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    Question micro the best review(115 usmle level mcqs)

    Virology

    Questions

    DIRECTIONS: Each question below contains five suggested responses.
    Please choose the one best response to each question.


    1. An HIV-positive patient asks you if you can tell him the chances of him
    progressing to symptomatic AIDS. Which one of the following tests would
    be most useful?
    a. CD4 lymphocyte count
    b. HIV antibody test
    c. HIV RT PCR
    d. Neopterin
    e. HIV p24 antigen


    2. Which of the following viruses causes an acute febrile rash and produces
    disease in immunocompetent children but has been associated with
    transient aplastic crises in persons with sickle cell disease?
    a. Rubeola
    b. Varicella-zoster
    c. Parvovirus
    d. Rubella
    e. Herpes simplex


    3. Infection with herpes simplex virus, a common human pathogen, is
    best described by which of the following statements?
    a. The CNS and visceral organs are usually involved
    b. It rarely recurs in a host who has a high antibody titer
    c. It can be reactivated by emotional disturbances or prolonged exposure to sunlight
    d. Initial infection usually occurs by intestinal absorption of the virus
    e. Infection with type 1 virus is most common



    4. The latest and most effective therapy for AIDS patients includes azidothymidine
    (AZT), dideoxyinosine (DDI), and saquinavir or similar
    agents. Use of these three drugs would inhibit which of the following viral
    processes?
    a. RNase, DNase
    b. gp120 formation
    c. p24 antibody expression
    d. All membrane synthesis
    e. Reverse transcriptase, protease


    5. An HIV-positive patient prior to being treated with AZT, DDI, and
    saquinavir has a CD4 lymphocyte count and an HIV RNA viral load test
    done. Results are as follows:
    CD4: 50 CD4 lymphocytes per microliter
    HIV RNA: 750,000 copies per ml
    Which of the following statements best describes the above patient?
    a. This patient is no longer in danger of opportunistic infection
    b. The 5-year prognosis is excellent
    c. The patient’s HIV screening test is most likely negative
    d. The patient is not infectious
    e. The viral load of 750,000 copies per ml suggests that the patient will respond
    to triple therapy



    6. This HIV-positive patient with a viral load of 750,000 copies of HIV
    RNA/ml and a total CD4 count of 50 is at an increased risk for a number of
    infectious diseases. For which of the following diseases is the patient at no
    more added risk than an immunocompetent host?
    a. Pneumocystic pneumonia
    b. Mycobacterial disease
    c. Kaposi’s sarcoma
    d. Pneumococcal pneumonia
    e. Herpes simplex virus



    7. Infectious mononucleosis, a viral disorder that can be debilitating, is
    characterized by which of the following statements?
    a. It is most prevalent in children less than 14 years old
    b. It is caused by a rhabdovirus
    c. The causative pathogen is an Epstein-Barr virus
    d. Affected persons respond to treatment with the production of heterophil antibodies
    e. Ribavirin is the treatment of choice



    8. A tube of monkey kidney cells is inoculated with nasopharyngeal secretions.
    During the next 7 days, no cytopathic effects (CPEs) are observed.
    On the eighth day, the tissue culture is infected accidentally with a picornavirus;
    nevertheless, the culture does not develop CPEs. The most likely
    explanation of this phenomenon is that
    a. The nasopharyngeal secretions contained hemagglutinins
    b. The nasopharyngeal secretions contained rubella virus
    c. Picornavirus does not produce CPEs
    d. Picornavirus does not replicate in monkey kidney cells
    e. Monkey kidney cells are resistant to CPEs



    9. The clinical picture of arbovirus infection fits one of three categories:
    encephalitis, hemorrhagic fever, or fever with myalgia. One of the characteristics
    of arboviruses is that they
    a. Are transmitted by arthropod vectors
    b. Are usually resistant to ether
    c. Usually cause symptomatic infection in humans
    d. Are closely related to parvoviruses



    10. Which one of the following statements best describes interferon’s suspected
    mode of action in producing resistance to viral infection?
    a. It stimulates a cell-mediated immunity
    b. It stimulates humoral immunity
    c. Its direct antiviral action is related to the suppression of messenger RNA formation
    d. Its action is related to the synthesis of a protein that inhibits translation or transcription
    e. It alters the permeability of the cell membrane so that viruses cannot enter the
    cell




    11. Coronaviruses are recognized by club-shaped surface projections that
    are 20 nm long and resemble solar coronas. These viruses are characterized
    by their ability to
    a. Infect infants more frequently than adults
    b. Cause the common cold
    c. Grow well in the usual cultured cell lines
    d. Grow profusely at 50°C
    e. Agglutinate human red blood cells



    12. Delta hepatitis only occurs in patients who also have either acute or
    chronic infection with hepatitis B virus. The delta agent is
    a. An incomplete hepatitis B virus
    b. Related to hepatitis A virus
    c. A hepatitis B mutant
    d. An incomplete RNA virus
    e. Hepatitis C



    13. Which of the following antiviral agents is a purine nucleoside analogue
    that has shown promise with Lassa fever, influenza A and B, and respiratory
    syncytial virus (RSV)?
    a. Amantadine
    b. Rimantadine
    c. Vidarabine
    d. Ribavirin
    e. Acyclovir



    14. Echoviruses are cytopathogenic human viruses that mainly infect the
    a. Respiratory system
    b. Central nervous system
    c. Blood and lymphatic systems
    d. Intestinal tract
    e. Bladder and urinary tract



    15. The most sensitive test for the diagnosis of herpes simplex (HSV)
    meningitis in a newborn infant is
    a. HSV IgG antibody
    b. HSV polymerase chain reaction (PCR)
    c. HSV culture
    d. Tzanck smear
    e. Cerebrospinal fluid (CSF) protein analysis




    16. Acute hemorrhagic conjunctivitis (AHC) is a contagious ocular infection
    characterized by pain, swelling of the eyelids, and subconjunctival
    hemorrhages. AHC has been reported to be caused by which of the following
    viruses?
    a. Coronavirus
    b. Reovirus
    c. Rhinovirus
    d. Enterovirus
    e. Respiratory syncytial virus




    17. Mumps virus accounts for 10 to 15% of all cases of aseptic meningitis
    in the United States. Infection with mumps virus
    a. Is apt to recur periodically in many affected persons
    b. Will usually cause mumps orchitis in postpubertal males
    c. Is maintained in a large canine reservoir
    d. Usually produces severe systemic manifestations
    e. Is preventable by immunization




    18. The serum of a newborn infant reveals a 1:32 cytomegalovirus (CMV)
    titer. The child is clinically asymptomatic. Which of the following courses
    of action would be advisable?
    a. Repeat the CMV titer immediately
    b. Wait 6 months and obtain another titer on the baby
    c. Obtain a CMV titer from all siblings
    d. Obtain an anti-CMV IgM titer from the mother
    e. Obtain an anti-CMV IgM titer from the baby




    19. A 3-year-old child presents at the physician’s office with symptoms of
    coryza, conjunctivitis, low-grade fever, and Koplik’s spots. The causative
    agent of this disease belongs to which group of viruses?
    a. Adenovirus
    b. Herpesvirus
    c. Picornavirus
    d. Orthomyxovirus
    e. Paramyxovirus





    20. One of the most common sexually transmitted diseases that may lead
    to cervical carcinoma is caused by which of the following viruses?
    a. Cytomegalovirus
    b. Papillomavirus
    c. Epstein-Barr virus
    d. Herpes simplex virus
    e. Adenovirus




    21. Which virus is the leading cause of the croup syndrome in young children
    and, when infecting mammalian cells in culture, will hemabsorb red
    blood cells?
    a. Group B coxsackievirus
    b. Rotavirus
    c. Parainfluenza virus
    d. Adenovirus

    e. Rhinovirus




    22. Hepatitis E, a recently characterized hepatitis virus, is best described
    by which of the following statements?
    a. It is not a threat to the blood supply
    b. It is a major cause of blood-borne hepatitis
    c. It is prevalent in North America
    d. It is a single-stranded DNA virus
    e. The disease resembles hepatitis C




    23. Meningitis is characterized by the acute onset of fever and stiff neck.
    Aseptic meningitis may be caused by a variety of microbial agents. During
    the initial 24 h of the course of aseptic meningitis, an affected person’s cerebrospinal
    fluid is characterized by
    a. Decreased protein content
    b. Elevated glucose concentration
    c. Lymphocytosis
    d. Polymorphonuclear leukocytosis
    e. Eosinophilia




    24. Infection with hepatitis D virus (HDV; delta agent) can occur simultaneously
    with infection with hepatitis B virus (HBV) or in a carrier of hepatitis
    B virus because HDV is a defective virus that requires HBV for its
    replicative function. What serologic test can be used to determine whether
    a patient with HDV is an HBV carrier?
    a. HBsAg
    b. HBc IgM
    c. HBeAg
    d. HBs IgM
    e. HBs IgG




    25. A nurse develops clinical symptoms consistent with hepatitis. She
    recalls sticking herself with a needle approximately 4 months before after
    drawing blood from a patient. Serologic tests for HBsAg, antibodies to
    HBsAg, and hepatitis A virus (HAV) are all negative; however, she is positive
    for IgM core antibody. The nurse
    a. Does not have hepatitis B
    b. Has hepatitis A
    c. Is in the late stages of hepatitis B infection
    d. Is in the “window” (after the disappearance of HBsAg and before the appearance
    of anti-HBsAg)
    e. Has hepatitis C




    26. Eastern equine encephalitis virus is associated with a high fatality rate.
    Control of the disease could be possible by eradication of
    a. Horses
    b. Birds
    c. Mosquitoes
    d. Fleas
    e. Ticks




    27. Adults who have had varicella as children occasionally suffer a recurrent
    form of the disease, shingles. The agent causing these diseases is a
    member of which of the following viral families?
    a. Herpesvirus
    b. Poxvirus
    c. Adenovirus
    d. Myxovirus
    e. Paramyxovirus




    28. Rhinovirus is primarily transmitted by
    a. Droplet aerosolization
    b. Sexual activity
    c. Fecal-oral route
    d. Fomites
    e. Vertical transmission from mother to child




    29. German measles virus (rubella), a common cause of exanthems in
    children, is best described by which of the following statements?
    a. Measles (rubeola) and German measles (rubella) are caused by the same virus
    b. Incubation time is approximately 3 to 4 weeks
    c. Vesicular rashes are characteristic
    d. Onset is abrupt with cough, coryza, and fever
    e. Specific antibody in the serum does not prevent disease




    30. The presence of Negri inclusion bodies in host cells is characteristic of
    a. Mumps
    b. Infectious mononucleosis
    c. Congenital rubella
    d. Aseptic meningitis
    e. Rabies




    31. Kuru is a fatal disease of certain New Guinea natives and is characterized
    by tremors and ataxia; Creutzfeldt-Jakob disease (CJD) is characterized
    by both ataxia and dementia. These diseases are thought to be caused
    by
    a. Slow viruses
    b. Cell wall–deficient bacteria
    c. Environmental toxins
    d. Prions
    e. Flagellates




    32. According to recommendations issued by the U.S. Public Health Service,
    which of the following statements regarding vaccination against
    smallpox is true?
    a. Pregnant women should be vaccinated in the first trimester
    b. Persons who have eczema should be vaccinated soon after diagnosis
    c. Persons who have immune deficiencies should be vaccinated every 5 years
    d. Persons traveling abroad need not be vaccinated
    e. Children should be vaccinated before they begin school




    33. Hepatitis D virus (delta agent) is a defective virus that can replicate
    only in cells already infected with which of the following viruses?
    a. Hepatitis A virus
    b. Epstein-Barr virus
    c. Hepatitis G virus
    d. Hepatitis B virus
    e. HIV




    34. A patient presents with keratoconjunctivitis. The differential diagnosis
    should include infection with which of the following viruses?
    a. Parvovirus
    b. Adenovirus
    c. Epstein-Barr virus
    d. Respiratory syncytial virus
    e. Varicella-zoster virus





    35. A hospital worker is found to have hepatitis B surface antigen. Subsequent
    tests reveal the presence of e antigen as well. The worker most likely
    a. Is infective and has active hepatitis
    b. Is infective but does not have active hepatitis
    c. Is not infective
    d. Is evincing a biologic false-positive test for hepatitis
    e. Has both hepatitis B and C




    36. Alphavirus causes which one of the following viral diseases?
    a. Marburg virus disease
    b. St. Louis encephalitis
    c. Western equine encephalitis
    d. Dengue
    e. Yellow fever





    37. Several antiviral compounds have been developed during the last
    decade. One such compound is ribavirin, a synthetic nucleoside structurally
    related to guanosine. Ribavirin therapy has been successfully used
    against
    a. Respiratory syncytial virus
    b. Herpes simplex virus
    c. Hepatitis B
    d. Group A coxsackievirus
    e. Parvovirus





    38. An immunocompromised person with history of seizures had an MRI
    that revealed a temporal lobe lesion. Brain biopsy results showed multinucleated
    giant cells with intranuclear inclusions. The most probable cause of
    the lesion is
    a. Hepatitis C virus
    b. Herpes simplex virus
    c. Listeria monocytogenes
    d. Coxsackievirus
    e. Parvovirus




    39. Which of the following procedures or clinical signs is most specific for
    the diagnosis of infectious mononucleosis caused by the Epstein-Barr
    virus?
    a. Laboratory diagnosis is based on the presence of “atypical lymphocytes” and
    EBV-specific antibody
    b. Growth in tissue culture cells
    c. Heterophile antibodies in serum
    d. Lymphadenopathy and splenomegaly on physical examination
    e. B-cell lymphocyte proliferation





    40. An infant, seen in the ER, presents with a fever and persistent cough.
    Physical examination and a chest x-ray suggest pneumonia. Which of the
    following is most likely the cause of this infection?
    a. Rotavirus
    b. Adenovirus
    c. Coxsackievirus
    d. Respiratory syncytial virus
    e. Rhinovirus





    41. Which one of the following groups of people may be at increased risk
    for HIV infection?
    a. Members of a household in which there is a person who is HIV-positive
    b. Receptionists at a hospital
    c. Factory workers whose coworkers are HIV-positive
    d. Foreign service employees who are hospitalized in Zaire for bleeding ulcers
    e. Homosexual females





    42. An obstetrician sees a pregnant patient who was exposed to rubella
    virus in the eighteenth week of pregnancy. She does not remember getting
    a rubella vaccination. The best immediate course of action is to
    a. Terminate the pregnancy
    b. Order a rubella antibody titer to determine immune status
    c. Reassure the patient because rubella is not a problem until after the thirtieth
    week
    d. Administer rubella immune globulin
    e. Administer rubella vaccine





    43. Mad Cow Disease has been highly publicized in Great Britain. This
    disease, which is similar to scrapie, is caused by
    a. A prion
    b. A virus
    c. Rickettsiae
    d. An autoimmune reaction
    e. A bacterium with a defective cell wall





    44. A patient has all the gastrointestinal symptoms of infection with
    hepatitis A virus (HAV), yet all the tests for HAV-IgG and HAV-IgM are nonreactive.
    A possible cause of this infection is
    a. Hepatitis B surface antigen
    b. Hepatitis C
    c. Hepatitis D
    d. Hepatitis E
    e. Rotavirus





    45. A 70-year-old nursing home patient refused the influenza vaccine and
    subsequently developed influenza. She died of acute pneumonia 1 week
    after contracting the “flu.” The most common cause of acute postinfluenzal
    pneumonia is
    a. Legionella
    b. Listeria
    c. Staphylococcus aureus
    d. Klebsiella
    e. Escherichia coli





    46. Which of the following viruses is primarily transmitted by the fecaloral
    route?
    a. St. Louis encephalitis virus
    b. Colorado tick fever virus
    c. Coxsackievirus
    d. Yellow fever virus
    e. Dengue fever virus





    47. Hantavirus is an emerging pathogen that is best described by which of
    the following statements?
    a. Influenza-like symptoms are followed rapidly by acute respiratory failure
    b. Hemolysis is common in infected patients
    c. It is acquired by inhalation of aerosols of the urine and feces of deer
    d. Transmission from human to human is common
    e. There is effective antiviral therapy available





    48. Erythema infectiosum (fifth disease), a self-limited disease of children,
    is caused by
    a. Measles
    b. Parvovirus
    c. Rubella
    d. Human herpesvirus type 6
    e. Norwalk virus





    49. Which one of the following viruses may be human tumor virus?
    a. Epstein-Barr virus (EBV)
    b. HIV
    c. Papillomavirus
    d. Varicella-zoster virus (VZV)
    e. Herpes simplex virus, type 2 (HSV)




    50. Parvovirus infection, the cause of a mild exanthem in children, is
    characterized by
    a. Epidemic acute respiratory disease
    b. Gastroenteritis
    c. Whooping cough–like disease
    d. Keratoconjunctivitis
    e. Acute hemolytic anemia






    51. Cytomegalovirus (CMV) infection is common. Which one of the following
    statements best characterizes CMV?
    a. It can be transmitted across the placental barrier
    b. While a common infection, CMV is almost always symptomatic
    c. The CMV can be cultured from red blood cells of infected patients
    d. Unlike other viral infections, CMV is not activated by immunosuppressive therapy
    e. There is no specific therapy for CMV





    52. Human rotaviruses are characterized by which of the following statements?
    a. They produce an infection that is primarily seen in adults
    b. They produce cytopathic effects in many conventional tissue culture systems
    c. They are lipid-containing RNA viruses possessing a double-shelled capsid
    d. They can be sensitively and rapidly detected in stools by the enzyme-linked
    immunosorbent assay (ELISA) technique
    e. They have been implicated as a major etiologic agent of infantile respiratory disease





    53. Subacute sclerosing panencephalitis virus (SSPE) is best described by
    which of the following statements?
    a. It is a progressive disease involving both white and gray matter
    b. It is a late CNS manifestation of mumps
    c. It is a common event occurring in 1 of 300,000 cases of mumps
    d. Viral DNA can be demonstrated in brain cells
    e. Demyelination is characteristic





    54. Rotavirus is a double-stranded RNA virus with a double-walled capsid.
    Which one of the following statements best describes rotavirus?
    a. There are no related animal viruses
    b. It is a major cause of neonatal diarrhea
    c. It is readily cultured from the stool of infected persons
    d. Maternal antibody does not appear to be protective
    e. Early breast-feeding offers no protection to neonates against it






    55. Paramyxoviruses are most commonly associated with which of the following
    diseases?
    a. Fifth disease
    b. Rubella
    c. Croup
    d. Tonsillitis
    e. Otitis media





    56. Human papillomavirus is most commonly associated with
    a. Rectal polyps
    b. Prostate cancer
    c. Condyloma acuminatum
    d. Hepatic carcinoma
    e. Carcinoma of the lung





    57. Reverse transcriptase is an enzyme unique to the retroviruses. Which
    one of the following is a function of the enzyme reverse transcriptase?
    a. DNase activity
    b. RNA-dependent RNA polymerase activity
    c. RNA isomerase activity
    d. RNA-dependent DNA polymerase activity
    e. Integration activity





    58. St. Louis encephalitis, a viral infection, was first recognized as an
    entity in 1933. Which of the following best describes SLE?
    a. It is transmitted to humans by the bite of an infected tick
    b. It is caused by a togavirus
    c. It is the major arboviral cause of central nervous system infection in the United
    States
    d. It may present initially with symptoms similar to influenza
    e. Laboratory diagnosis is routinely made by cultural methods






    59. There is considerable overlap of signs and symptoms seen in congenital
    and perinatal infections. In a neonate with “classic” symptoms of congenital
    cytomegalovirus (CMV) infection, which one of the following tests
    would be most useful in establishing a diagnosis?
    a. CMV IgG titer on neonate’s serum at birth
    b. CMV IgG titer on mother’s serum at birth of infant
    c. CMV IgM titer on neonate’s serum at birth and at 1 month of age
    d. Total IgM on neonate’s serum at birth
    e. Culture of mother’s urine





    60. Interferon, a protein that inhibits viral replication, is produced by cells
    in tissue culture when the cells are stimulated with which of the following?
    a. Botulinum toxin
    b. Synthetic polypeptides
    c. Viruses
    d. Chlamydiae
    e. Gram-positive bacteria






    61. Which one of the following statements best describes the cytopathic
    effects of viruses on host cells?
    a. Usually morphological in nature
    b. Often associated with changes in mitochondrial membranes
    c. Pathognomonic for an infecting virus
    d. Rarely fatal to the host cell
    e. Can only be seen with an electron microscope





    62. A 17-year-old girl presents with cervical lymphadenopathy, fever, and
    pharyngitis. Infectious mononucleosis is suspected. The most rapid and
    clinically useful test to make this diagnosis is
    a. IgM antibody to viral core antigen (VCA)
    b. IgG antibody to VCA
    c. Antibody to Epstein-Barr nuclear antigen (EBNA)
    d. Culture
    e. C reactive protein (CRP)





    63. Which one of the following viruses would be most likely to establish a
    latent infection?
    a. Adenovirus
    b. Measles virus
    c. Influenza virus
    d. Parvovirus
    e. Coxsackievirus group B





    64. A regimen that includes appropriately administered gamma globulin
    may be contraindicated in which one of the following diseases?
    a. Hepatitis A
    b. Hepatitis B
    c. Rabies
    d. Poliomyelitis
    e. Infectious mononucleosis





    65. Atypical lymphocytosis is most likely to be found in which one of the
    following diseases?
    a. Encephalitis caused by herpes simplex virus (HSV)
    b. Mononucleosis induced by Epstein-Barr virus
    c. Parvovirus infection
    d. Chronic hepatitis C
    e. Rotavirus gastroenteritis





    66. A patient has arthralgia, a rash, lymphadenopathy, pneumonia but no
    fever. Which of the following diseases is most likely based on these symptoms?
    a. Dengue fever
    b. St. Louis encephalitis
    c. Infectious mononucleosis
    d. Hepatitis
    e. HIV infection






    67. Hepatitis C (HCV) is usually a clinically mild disease, with only minimal
    elevation of liver enzymes. Hospitalization is unusual. Which one of
    the following statements best characterizes HCV?
    a. Few cases progress to chronic liver disease
    b. It often occurs in posttransfusion patients
    c. HBV but not HCV infections occur in IV drug abusers
    d. It is a DNA virus
    e. Blood products are not tested for antibody to HCV





    68. Which of the following markers is usually the first viral marker
    detected after hepatitis B infection?
    a. HBeAg
    b. HBsAg
    c. HBcAg
    d. Anti-HBc
    e. HbeAb




    69. Which of the following may be the only detectable serological marker
    during the early convalescent phase of HBV infection (window phase)?
    a. HBeAg
    b. HBsAg
    c. HBcAg
    d. Anti-HBc
    e. HbeAb





    70. Which one of the following markers is closely associated with HBV
    infectivity and DNA polymerase activity?
    a. HBeAg
    b. HBsAg
    c. HBcAg
    d. Anti-HBc
    e. HBeAb




    71. Which of the following is found within the nuclei of infected hepatocytes
    and not usually in the peripheral circulation?
    a. HBeAg
    b. HBsAg
    c. HBcAg
    d. Anti-HBc
    e. HbeAb






    72. Which one of the following viruses is the leading cause of congenital
    malformations?
    a. Rabies
    b. Rhinovirus
    c. Cytomegalovirus
    d. Respiratory syncytial virus
    e. Mumps




    73. Orchitis, which may cause sterility, is a possible manifestation of
    which of the following?
    a. Rabies
    b. Rhinovirus
    c. Cytomegalovirus
    d. Respiratory syncytial virus
    e. Mumps




    74. Which of the following is a leading cause of pneumonia primarily in
    infants?
    a. Rabies
    b. Rhinovirus
    c. Cytomegalovirus
    d. Respiratory syncytial virus
    e. Mumps





    75. Which of the following causes a fatal encephalitis for which a vaccine
    is available?
    a. Rabies
    b. Rhinovirus
    c. Cytomegalovirus
    d. Respiratory syncytial virus
    e. Mumps





    76. Traditional vaccination for the common cold is virtually impossible
    because there are multiple serotypes of which one of the following viruses?
    a. Rabies
    b. Rhinovirus
    c. Cytomegalovirus
    d. Respiratory syncytial virus
    e. Mumps






    77. Which of the following is available and effective for hepatitis A?
    a. Acyclovir
    b. Killed virus vaccine
    c. Inactivated virus vaccine
    d. Live virus vaccine
    e. Recombinant viral vaccine





    78. Patients should be vaccinated annually for influenza with which of the
    following vaccines?
    a. Immune serum globulin
    b. Killed virus vaccine
    c. Inactivated virus vaccine
    d. Live virus vaccine
    e. Recombinant viral vaccine





    79. The vaccine for measles is best characterized as a
    a. Bacterin
    b. Killed virus vaccine
    c. Inactivated virus vaccine
    d. Live virus vaccine
    e. Recombinant viral vaccine





    80. Which one of the following would be the treatment of choice for HSV
    infection?
    a. Acyclovir
    b. Killed virus vaccine
    c. Herpes immune globulin
    d. Azythromycin
    e. Recombinant viral vaccine




    81. Which of the following best describes the presently available vaccine
    for hepatitis B?
    a. Synthetic peptide vaccine
    b. Killed virus vaccine
    c. Inactivated virus vaccine
    d. Live virus vaccine
    e. Recombinant viral vaccine






    82. Chicken pox is a common disease of childhood. It is caused by which
    of the following viruses?
    a. Cytomegalovirus
    b. Rotavirus
    c. Varicella-zoster virus
    d. Adenovirus
    e. Papillomavirus





    83. Excluding influenza, which one of the following viruses is a common
    cause of acute respiratory disease?
    a. Cytomegalovirus
    b. Rotavirus
    c. Varicella-zoster virus
    d. Adenovirus
    e. Papillomavirus





    84. Human warts are not only cosmetically unsightly but may lead to cancer
    of the cervix. They are caused by which one of the following viruses?
    a. Cytomegalovirus
    b. Rotavirus
    c. Varicella-zoster virus
    d. Adenovirus
    e. Papillomavirus





    85. A vaccine is available for one of the most common causes of infantile
    gastroenteritis. However, it has recently been recalled. The virus is
    a. Cytomegalovirus
    b. Rotavirus
    c. Varicella-zoster virus
    d. Adenovirus
    e. Papillomavirus





    86. A child has mononucleosis-like symptoms yet the test for mononucleosis
    and the EBV titers are negative. One of the causes of heterophilenegative
    mononucleosis is
    a. Cytomegalovirus
    b. Herpes simplex virus
    c. Varicella-zoster virus
    d. Adenovirus
    e. Coxsackievirus
    24 Microbiology





    87. Malaise and fatigue with increased “atypical” lymphocytes and a reactive
    heterophil antibody test is most commonly caused by
    a. Toxoplasma
    b. Borrelia burgdorferi
    c. Epstein-Barr virus
    d. Parvovirus
    e. Rubella virus






    88. Lethargy, malaise, and fatigue are observed in a patient 2 weeks after
    eating raw hamburger at a restaurant. The most likely infectious cause is
    a. Toxoplasma
    b. Cytomegalovirus
    c. E. coli
    d. Salmonella
    e. Clostridium





    89. Burkitt’s lymphoma is characterized by elevated “early antigen” tests
    with a restricted pattern of fluorescence. This disease is caused by
    a. Cytomegalovirus
    b. B. burgdorferi
    c. Epstein-Barr virus
    d. Lymphogranuloma venereum
    e. Herpes simplex virus






    90. This virus may be detected by the polymerase chain reaction (PCR) in
    a variety of cells of patients with nasopharyngeal carcinoma.
    a. Measles
    b. Mumps
    c. Rubella
    d. Parvovirus
    e. Epstein-Barr virus






    91. This virus causes a mononucleosis-like syndrome caused by a latent
    herpesvirus; it is often a congenital infection. Large amounts of the virus
    are excreted in the urine; thus, urine becomes the fluid of choice for diagnosis
    of this disease.
    a. Epstein-Barr virus
    b. Cytomegalovirus
    c. HHV-6
    d. Parvovirus
    e. Norwalk virus





    Questions 92–96



    Assume you are asked by a resident what the most appropriate specimen is
    for the detection of a particular virus.



    92. Human papillomavirus
    a. Cervical tissue
    b. Synovial fluid
    c. Blood
    d. Skin




    93. Cytomegalovirus
    a. Cervical tissue
    b. Synovial fluid
    c. Blood
    d. Skin
    e. Cerebrospinal fluid




    94. Enterovirus
    a. Cervical tissue
    b. Synovial fluid
    c. Blood
    d. Skin
    e. Cerebrospinal fluid






    95. Varicella-zoster virus (VZV)
    a. Cervical tissue
    b. Synovial fluid
    c. Blood
    d. Skin
    e. Cerebrospinal fluid





    96. Adenovirus 40/41
    a. Cervical tissue
    b. Synovial fluid
    c. Blood
    d. Stool
    e. Cerebrospinal fluid





    97. Which of the following is transmitted by the fecal-oral route; can be
    acquired from shellfish; and often causes acute jaundice, diarrhea, and liver
    function abnormalities?
    a. Rotavirus
    b. Adenovirus 40/41
    c. Norwalk virus
    d. Astrovirus
    e. Hepatitis A virus





    98. Which of the following is the second most common cause of pediatric
    gastroenteritis? Unlike other similar viruses, this virus causes only gastroenteritis.
    a. Rotavirus
    b. Adenovirus 40/41
    c. Norwalk virus
    d. Astrovirus
    e. Hepatitis A virus




    99. Which of the following is the most common cause of pediatric gastroenteritis?
    It is difficult to grow in cell culture but can be detected easily
    by immunologic methods (ELISA).
    a. Rotavirus
    b. Adenovirus 40/41
    c. Norwalk virus
    d. Astrovirus
    e. Hepatitis A virus






    100. Which of the following is a common cause of epidemic gastroenteritis,
    particularly aboard cruise ships and in summer camps? It may be
    detected by ELISA methods or electron microscopy.
    a. Rotavirus
    b. Adenovirus 40/41
    c. Norwalk virus
    d. Astrovirus
    e. Hepatitis A virus





    101. Which of the following is a cause of mild gastroenteritis? It can be
    transmitted by the fecal-oral route but not by food consumption.
    a. Rotavirus
    b. Adenovirus 40/41
    c. Norwalk virus
    d. Astrovirus
    e. Hepatitis A virus






    102. IgM antibody to the viral particle is the method of choice for laboratory
    diagnosis of which one of the following hepatitis viruses?
    a. Hepatitis A
    b. Hepatitis B
    c. Hepatitis C
    d. Hepatitis D
    e. Hepatitis E






    103. This virus belongs to the family of flaviviruses and its reservoir is
    strictly human. Transmission is blood-borne so the blood supply is routinely
    screened for this virus.
    a. Hepatitis A
    b. Hepatitis B
    c. Hepatitis C
    d. Hepatitis D
    e. Hepatitis E







    104. Vaccination for this hepatic disease is with viral surface antigen and
    usually provides immunity.
    a. Hepatitis A
    b. Hepatitis B
    c. Hepatitis C
    d. Hepatitis D
    e. Hepatitis E





    105. This hepatitis virus is a calicivirus. The reservoir is in pigs, and
    humans acquire it via the fecal-oral route.
    a. Hepatitis A
    b. Hepatitis B
    c. Hepatitis C
    d. Hepatitis D
    e. Hepatitis E





    106. This hepatitis virus is a defective virus in that it cannot replicate
    independently without the presence of hepatitis B virus.
    a. Hepatitis A
    b. Hepatitis B
    c. Hepatitis C
    d. Hepatitis D
    e. Hepatitis E






    107. Which of the following is the causative agent of a variety of cutaneous
    warts (plantar, common, and flat) and is associated with cervical neoplasia?
    a. Human papillomavirus
    b. West Nile virus
    c. Tick-borne encephalitis virus
    d. Polyomavirus
    e. Subacute sclerosing panencephalitis virus (SSPE)







    108. Recently appearing in the United States, this virus is carried by birds,
    transmitted by mosquitoes, and infects humans and horses.
    a. Human papillomavirus
    b. West Nile virus
    c. Tick-borne encephalitis virus
    d. Polyomavirus
    e. SSPE






    109. Which of the following viruses causes progressive multifocal
    leukoencephalopathy (PML), a disease causing demyelination in the central
    nervous system?
    a. Human papillomavirus
    b. West Nile virus
    c. Tick-borne encephalitis virus
    d. Polyomavirus
    e. SSPE







    110. This virus is transmitted by the same arthropod that transmits
    babesiosis and ehrlichiosis.
    a. Human papillomavirus
    b. West Nile virus
    c. Tick-borne encephalitis virus
    d. Polyomavirus
    e. SSPE






    111. This virus is a single-stranded RNA orthomyxovirus. Annual vaccination
    is necessary because of antigenic drift and shift.
    a. Measles virus
    b. Influenza virus
    c. Respiratory syncytial virus
    d. Parainfluenza virus
    e. Adenovirus






    112. This virus is a single-stranded RNA paramyxovirus. The rash known
    as Koplik’s spots is pathognomonic.
    a. Measles virus
    b. Influenza virus
    c. Respiratory syncytial virus
    d. Parainfluenza virus
    e. Adenovirus







    113. This virus is the leading cause of bronchiolitis and communityacquired
    pneumonia in infants.
    a. Measles virus
    b. Influenza virus
    c. Respiratory syncytial virus
    d. Parainfluenza virus
    e. Adenovirus






    114. This is a paramyxovirus and causes the syndrome known as croup.
    a. Measles virus
    b. Influenza virus
    c. Respiratory syncytial virus
    d. Parainfluenza virus
    e. Adenovirus







    115. This is a double-stranded DNA virus. It is responsible for 15% of
    pediatric respiratory infections and 10 to 15% of acute diarrhea in children.
    a. Measles virus
    b. Influenza virus
    c. Respiratory syncytial virus
    d. Parainfluenza virus
    e. Adenovirus

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    Virology
    Answers
    [HIDE]1. The answer is c.

    (Ryan, pp 552–554.) HIV RT PCR, a nucleic acid
    amplification test for HIV RNA, has recently been shown to be the most
    valuable test for a) monitoring a patient’s progress during triple drug therapy
    and b) determining the chances of progression to AIDS. A viral load of
    750,000 copies per ml significantly increases the chance of progression to
    AIDS within 5 years. The other tests listed do not accurately predict progression
    to AIDS. The figure below shows the basic structure of HIV
    including the enzyme, reverse transcriptase.





    2. The answer is c.

    (Davis, pp 927–928. Raoult, p 785.) Parvovirus B 19 is
    the causative agent of erythema infectiosum (fifth disease). It is associated
    with transient aplastic crisis in persons with hereditary hemolytic anemia.
    In adults, it is also associated with polyarthralgia.





    3. The answer is c.

    (Davis, p 935. Raoult, pp 470–474.) The initial infection
    by herpes simplex virus is often inapparent and occurs through a
    break in the skin or mucous membranes, such as in the eye, throat, or genitals.
    Latent infection often persists at the initial site despite high antibody
    titers. Recurrent disease can be triggered by temperature change, emotional
    distress, and hormonal factors. Type 1 herpes simplex virus is usually, but
    not exclusively, associated with ocular and oral lesions; type 2 is usually,
    but not exclusively, associated with genital and anal lesions. Type 2 infection
    is more common. In addition to mucocutaneous infections, the CNS
    and occasionally visceral organs can be involved.




    4–6. The answers are 4-e, 5-e, 6-d.

    (Levinson, pp 271–279.) The advent
    of triple therapy or a therapeutic “cocktail” has had a marked effect on
    AIDS patients. The combination of drugs work together as reverse transcriptive
    inhibitors and a protease inhibitor. Patients improve rapidly, their
    CD4 lymphocyte counts increase, and their HIV viral load is drastically
    reduced, often to 50 copies per ml. On the other hand, an untreated HIVpositive
    patient with a low CD4 and a high viral load a) is at increased risk
    of opportunistic infection and b) has a much greater chance of developing
    AIDS than if the viral load was 50,000. The patient is infectious and his
    HIV antibody screening test will be positive. The high viral load, however,
    is not a predictor of response to therapy. Many patients with high viral
    loads do very well on triple therapy, although resistance to one or more of
    the agents may subsequently occur. A low CD4 count does not predict progression
    to AIDS but does indicate increased chance of opportunistic infection
    such as those listed. Kaposi’s sarcoma, which has been linked to
    herpesvirus type 8, pneumocystis, and mycobacterial disease are three of
    the most prevalent opportunistic infections. While HIV-positive patients
    contract pneumococcal pneumonia, they are probably at no more risk than
    the general population, as protection against pneumococcal disease is
    linked to the presence of anticapsular antibody.




    7. The answer is c.

    (Murray, pp 912–918.) All of Koch’s postulates have
    been verified for the relationship between infectious mononucleosis and
    Epstein-Barr virus, a herpesvirus. However, the relationship between this
    virus and Burkitt’s lymphoma, sarcoid, and systemic lupus erythematosus
    (SLE) is less clear. Infectious mononucleosis is most common in young
    adults (14 to 18 years of age) and is very rare in young children. There is
    no specific treatment. Heterophil antibody titer is helpful in diagnosis, but
    is not expressed as a function of clinical recovery.




    8. The answer is b.

    (Levinson, pp 231–232.) Rubella virus does not produce
    cytopathic effects (CPEs) in tissue-culture cells. Moreover, rubellainfected
    cells challenged with a picornavirus are resistant to subsequent
    infection and thus would not exhibit CPEs. Monkey kidney cells infected
    only with picornavirus would show CPEs.





    9. The answer is a.

    (Levinson, pp 252–256.) Arboviruses (arthropodborne
    viruses) may or may not be surrounded by a lipid envelope,
    although most are inactivated by lipid solvents such as ether and may contain
    either double-stranded or single-stranded RNA. Physicochemical studies
    have demonstrated a great heterogeneity among these viruses.
    Arboviruses cause disease in vertebrates; in humans, encephalitis is a frequent
    arbovirus illness. Most human infections with arbovirus, however,
    are asymptomatic.





    10. The answer is d.

    (Levinson, pp 190–191.) Interferon is a protein produced
    by cells in response to a viral infection or certain other agents. Entering
    uninfected cells, interferon causes production of a second protein that
    alters protein synthesis. As a result of inhibition of either translation or
    transcription, new viruses are not assembled following infection of interferon-
    protected cells.





    11. The answer is b.

    (Raoult, p 250.) Coronaviruses, discovered in 1965,
    are thought to be a major agent of the common cold, especially in older
    children and adults. The virion is known to contain RNA, but other elements
    of its structure are unclear. At 34C, viral multiplication is profuse;
    however, infectivity is greatly reduced at higher temperatures or following
    extended incubation.




    12. The answer is d.

    (Levinson, pp 249–250.) The delta agent was first
    described in 1977 and has recently been shown to be an incomplete RNA
    virus that requires HBsAg for replication. It is found most often in persons
    who have multiple parenteral exposures, for example, intravenous (IV)
    drug abusers, hemophiliacs, and multiply transfused patients.






    13. The answer is d.

    (Raoult, pp 555–557.) As an intravenous agent, ribavirin
    is effective against Lassa fever in the first week of onset of the disease.
    It may also be administered as an aerosol that is quite useful in infants with
    RSV. Unlike amantadine, which is efficacious only with influenza A, ribavirin
    has activity against both influenza A and B if administered by aerosol
    in the first 24 h of onset.





    14. The answer is d.

    (Levinson, p 239.) Echoviruses were discovered accidentally
    during studies on poliomyelitis. They were named enteric cytopathogenic
    human orphan (ECHO) viruses because, at the time, they had not been
    linked to human disease and thus were considered “orphans.” Echoviruses
    now are known to infect the intestinal tract of humans; they also can cause
    aseptic meningitis, febrile illnesses, and the common cold. Echoviruses
    range in size from 24 to 30 nm in diameter and contain a core of RNA.




    15. The answer is b.

    (Levinson, pp 208–216.) HSV meningitis or
    encephalitis is difficult to diagnose by laboratory tests as there is a low titer
    of virus present in the CSF. Neonatal HSV infects the child during the birth
    process. While culture, Tzanck smear, and even antibody tests may be useful
    in adults, particularly those with HSV-rich lesions, they are not useful
    for CSF testing. Only PCR is sensitive enough to detect HSV DNA in the
    CSF. Once diagnosed rapidly, HSV encephalitis or meningitis can be treated
    with acyclovir.





    16. The answer is d.

    (Levinson, pp 238–239.) Enterovirus and Coxsackievirus
    A can be recovered from conjunctival scrapings of patients with
    acute hemorrhagic conjunctivitis (AHC) during the first 3 days of illness.
    Isolation rates are somewhat higher for enterovirus than Coxsackievirus.
    Less than 5% of throat swab or fecal specimens have been positive for
    either virus.





    17. The answer is e.

    (Levinson, pp 228–229.) Much of the public’s understanding
    of mumps is based on suppositions that are without any scientific
    basis. For example, natural mumps infection confers immunity after a single
    infection, even if the infection was a unilateral, not bilateral, parotitis.
    Also, sterility from mumps orchitis is not assured; only 20% of males older
    than 13 years of age develop orchitis. The majority of patients with mumps
    do not develop systemic manifestations. In fact, some do not develop
    parotitis. Last, the virus is maintained exclusively in human populations;
    canine reservoirs are not known. The mumps vaccine is a live attenuated
    virus vaccine derived from chick-embryo tissue culture.





    18. The answer is e.

    (Levinson, pp 213–214.) Clinical manifestations of
    cytomegalovirus (CMV) infection may not be readily apparent at birth.
    Thus, in a newborn infant with a 1:32 titer of CMV, it is necessary to determine
    whether the antibodies were passed transplacentally from the mother
    (these antibodies would be IgG) or produced by the fetus in response to an
    in utero infection (IgM). A newborn infant who is infected excretes large
    numbers of virus particles in the urine and, therefore, places other
    neonates at risk for contracting CMV disease.





    19. The answer is e.


    (Raoult, pp 619–628.) Koplik’s spots are pathognomonic
    for measles. The measles virus is a paramyxovirus. In industrialized
    countries, vaccination has reduced the importance of this childhood infection
    (although U.S. incidence increased in 1989 and 1990). In developing
    countries, however, measles is a major killer of young children. In America,
    most states now require proof of immunity before school enrollment, and
    this has reduced the incidence of disease.







    20. The answer is b.

    (Levinson, pp 219–220.) Human papillomavirus
    (HPV) is the cause of genital warts. It is one of the most pervasive of all the
    sexually transmitted diseases. There is no specific cure or vaccine. There are
    multiple serotypes of papillomavirus and some serotypes are linked to cervical
    cancer. New techniques for molecular diagnosis of HPV show promise
    for rapid and sensitive detection and perhaps more aggressive treatment.




    21. The answer is c.

    (Levinson, pp 230–231.) Parainfluenza viruses are
    important causes of respiratory diseases in infants and young children. The
    spectrum of disease caused by these viruses ranges from a mild febrile cold
    to croup, bronchiolitis, and pneumonia. Parainfluenza viruses contain
    RNA in a nucleocapsid encased within an envelope derived from the host
    cell membrane. Infected mammalian cell culture will hemabsorb red blood
    cells owing to viral hemagglutinin on the surface of the cell.





    22. The answer is a.

    (Levinson, pp 250–251.) Hepatitis E is a newly recognized
    single-stranded RNA virus in the calicivirus family. Epidemics
    have been observed in Asia, Africa, India, and Mexico. Like HAV, it is enterically
    transmitted but there is no vaccine available nor routine detection
    test. Chronic liver disease does not occur, and because it is not blood-borne
    it is of no threat to the blood supply.





    23. The answer is d.

    (Levinson, pp 238–239.) Aseptic meningitis is characterized
    by a pleocytosis of mononuclear cells in the cerebrospinal fluid;
    polymorphonuclear cells predominate during the first 24 h, but a shift to
    lymphocytes occurs thereafter. The cerebrospinal fluid of affected persons is
    free of culturable bacteria and contains normal glucose and slightly elevated
    protein levels. Peripheral white blood cell counts usually are normal.
    Although viruses are the most common cause of aseptic meningitis, spirochetes,
    chlamydiae, and other microorganisms also can produce the disease.






    24. The answer is b.

    (Levinson, pp 189, 206, 246.) In a chronic HBV carrier,
    there would be no HB core IgM antibody, whereas it would be present
    in a new HBV infection. The HBe antigen could be present in either an HBV
    carrier or in acute infection. HBsAg would be present in either a new infection
    or in the carrier state, while HBsAb would not be present in either case.





    25. The answer is d.

    (Levinson, pp 243–247.) In a small number of
    patients with acute hepatitis B infection, HBsAg can never be detected. In
    others, HBsAg becomes negative before the onset of the disease or before
    the end of the clinical illness. In such patients with acute hepatitis, hepatitis
    B virus infection may only be established by the presence of antihepatitis
    B core IgM (anti-HBc IgM), a rising titer of anti-HBc, or the
    subsequent appearance of anti-HBsAg.






    26. The answer is c.

    (Levinson, pp 253–254.) Eastern equine encephalitis
    (EEE) is a severe disease usually seen in the summer months when Aedes
    mosquitoes are prevalent. In 1996 and 1997, there were several outbreaks
    in the Northeast United States. Control of EEE is a function of mosquito
    eradication. Horses and humans are accidental hosts. While draining of
    swamps helps, other measures to eliminate mosquitoes such as spraying
    are the most effective.





    27. The answer is a.

    (Levinson, pp 212–213.) Varicella-zoster virus, a
    member of the herpesvirus group, causes a usually mild, self-limited illness
    in children. Recurrent disease in adults who possess circulating antibody
    against varicella-zoster virus may be more severe and cause an inflammatory
    reaction in the sensory ganglia of spinal or cranial nerves. This disease,
    shingles, appears to result from the reactivation (by trauma or other stimuli)
    of latent varicella-zoster virus.






    28. The answer is d.

    (Levinson, pp 239–240.) Rhinovirus is a major cause
    of the common cold. The primary mode of transmission is the contact of
    contaminated hands, fingers, or fomites with the conjunctiva or nasal
    epithelium. While several studies have shown no evidence of aerosol transmission,
    a study by Dick and associates in 1986 did show aerosol transmission
    can occur. This is not, however, the main mode of transmission.





    29. The answer is d.

    (Levinson, pp 227–228.) Measles (rubeola) is an
    acute, highly infectious disease characterized by a maculopapular rash. German
    measles (rubella) is an acute, febrile illness characterized by a rash as
    well as suboccipital lymphadenopathy. Incubation time is 9 full days after
    exposure. Onset is abrupt and symptoms mostly catarrhal. Koplik’s spots,
    pale, bluish-white spots in red areolas, can frequently be observed on the
    mucous membranes of the mouth and are pathognomonic for measles.




    30. The answer is e.

    (Levinson, pp 232–234.) The definitive diagnosis of
    rabies in humans is based on the finding of Negri bodies, which are cytoplasmic
    inclusions in the nerve cells of the spinal cord and brain, especially
    in the hippocampus. Negri bodies are eosinophilic and generally spherical
    in shape; several may appear in a given cell. Negri bodies, although
    pathognomonic for rabies, are not found in all cases of the disease.




    31. The answer is d.

    (Levinson, pp 268–271.) Kuru and Creutzfeldt-
    Jakob disease (CJD) are similar but not identical diseases with very different
    epidemiology. Kuru is prevalent among certain tribes in New Guinea
    who practiced ritual cannibalism by eating the brains of the departed. CJD
    is found worldwide and has been transmitted by corneal transplants and in
    pituitary hormone preparations. There is some association between CJD
    and Mad Cow Disease in England. Prions are unconventional selfreplicating
    proteins, sometimes called amyloid. It is now thought that CJD,
    Kuru, and animal diseases such as scrapie, visna, and bovine spongiform
    encephalopathy (Mad Cow Disease) are caused by prions.






    32. The answer is d.

    (Levinson, pp 216–217.) Routine vaccination of
    infants and children for smallpox has been discontinued in the United
    States, both because the risk of contracting the disease is so low and
    because the complications of smallpox vaccination, including generalized
    vaccinia eruption, postvaccinal encephalitis, and fetal vaccinia, are significant.
    Owing to the extremely effective eradication of smallpox worldwide
    by the World Health Organization, U.S. citizens traveling abroad no longer
    require vaccination. Pregnancy, immune deficiencies, and eczema and
    other chronic dermatitides are contraindications to smallpox vaccination.






    33. The answer is d.

    (Ryan, pp 422–500.) Hepatitis D virus is a defective
    virus with an RNA genome and a hepatitis B surface antigen envelope. Two
    types of HDV infection occur: simultaneous HDV and HBV infection, or
    HDV superinfection with chronic HBV infection. Diagnosis is made by
    demonstrating IgM or IgG antibodies, or both.





    34. The answer is b.

    (Levinson, pp 218–219.) Adenovirus type 8 is associated
    with epidemic keratoconjunctivitis, while adenovirus types 3 and 4
    are often associated with “swimming pool conjunctivitis.” There are also
    reports of nosocomial conjunctivitis with adenovirus. Herpes simplex virus
    can infect the conjunctiva and is among the most common causes of blindness
    in North America and Europe.






    35. The answer is a.

    (Levinson, pp 243–246.) The e antigen seems to be
    related to the Dane particle, which is presumed to be the intact hepatitis B
    virus. Possession of the e antigen suggests active disease and, thus, an
    increased risk of transmission of hepatitis to others. HBsAg and e antigen
    are components of hepatitis B and are not shared by other hepatitis
    viruses.






    36. The answer is c.

    (Levinson, pp 253–255.) St. Louis encephalitis, yellow
    fever, and dengue are caused by flaviviruses. Western equine encephalitis
    is caused by an alphavirus. Laboratory diagnosis is usually made by
    demonstration of a fourfold rise in specific antibody titer in paired sera.






    37. The answer is a.

    (Levinson, p 201.) Ribavirin is effective to varying
    degrees against several RNA- and DNA-containing viruses in vitro. It has
    been approved for aerosol treatment of respiratory syncytial virus infec-
    tions in infants. Intravenous administration has proved effective in treating
    Lassa fever.





    38. The answer is b.

    (Ryan, p 505.) Herpes simplex virus causes primary
    and recurrent disease. The typical skin lesion is a vesicle that contains virus
    particles in serous fluid. Giant multinucleated cells are typically found at
    the base of the herpesvirus lesion. Encephalitis, which usually involves the
    temporal lobe, has a high mortality rate. Severe neurologic sequelae are
    seen in surviving patients.





    39. The answer is b.

    (Ryan, pp 514–515.) Contact with infected secretions
    such as saliva can result in infection with EBV, thus the term kissing
    disease. Laboratory diagnosis of EBV-induced infectious mononucleosis is
    usually determined by presence of atypical lymphocytes, heterophile antibodies,
    or specific antiviral antibodies such as VCA (viral capsid antibody).





    40. The answer is d.

    (Baron, pp 731–732.) Respiratory syncytial virus
    (RSV) is the most important cause of pneumonia and bronchiolitis in
    infants. The infection is localized to the respiratory tract. The virus can be
    detected rapidly by immunofluorescence on smears of respiratory epithelium.
    In older children, the infection resembles the common cold.
    Aerosolized ribavirin is recommended for severely ill hospitalized infants.





    41. The answer is d.


    (Howard, pp 838–840.) Many believe that casual
    contact with patients who are HIV-positive increases the risk of acquiring
    the disease. This is not the case. It is also clear that homosexual females
    have a low rate of HIV acquisition. Because a substantial portion of the
    blood supply in Central African countries is HIV-infected, hospitalization is
    risky particularly if transfusion is necessary.






    42. The answer is b.

    (Howard, pp 819–821.) The highest risk of fetal
    infection with rubella occurs during the first trimester. In seronegative
    patients, the risk of infection exceeds 90%. However, before other measures
    (such as termination of pregnancy) are considered, a rubella immune
    status must be performed. A rubella titer of 1:10 is protective.






    43. The answer is a.

    (Howard, pp 755–756.) Mad Cow Disease is related
    to both scrapie in sheep and bovine spongiform encephalopathy virus. The
    fear in Great Britain is the potential for acquiring Creutzfeldt-Jakob disease,
    which is a slowly progressive neurodegenerative disease. Theoretically, such
    acquisition could be through ingestion of beef from infected cows. A prion
    consists of protein material without nucleic acid. While related to a virus, a
    prion is a proteinaceous infectious particle that replicates within cells.






    44. The answer is d.

    (Howard, pp 755–756.) Hepatitis E virus (HEV) is a
    single-stranded RNA virus. It is transmitted enterically, and the disease is
    often referred to as enteric hepatitis C. There is no test for HEV routinely
    available. Diagnosis is clinical and also one of exclusion.




    45. The answer is c.

    (Levinson, pp 47, 87.) Staphylococcus aureus is the
    most common cause of postinfluenzal secondary bacterial pneumonia. It
    most often affects the elderly, although patients of any age may be afflicted.
    The pneumococcus as well as group A streptococci and Haemophilus
    influenzae may also cause pneumonia.





    46. The answer is c.

    (Levinson, pp 253–256.) St. Louis encephalitis virus
    is spread by mosquitoes and causes a severe encephalitis with a near 10%
    fatality rate. Colorado tick fever, spread by the wood tick, causes fever,
    headache, retro-orbital pain, and severe myalgia. Fever and jaundice characterize
    yellow fever, a life-threatening disease spread by mosquitoes. Following
    fever, headache, myalgias, and photophobia, the symptoms
    progress to the liver, kidney, and heart. Mortality rate is high. Dengue fever
    shares the same mosquito vector as yellow fever. Classic dengue fever
    (breakbone fever) includes flu-like symptoms. Severe muscle and joint
    (breakbone) pain occurs. Coxsackievirus is spread by the fecal-oral route.






    47. The answer is a.

    (Levinson, p 280.) In 1993, an outbreak of a fatal
    respiratory disease occurred in the southwestern United States. This disease
    is caused by a Hantavirus endemic in deer mice. It is not transmitted
    from person to person. The mortality rate is 60%. Ribavirin has been used
    but is not effective. A vaccine is not available.






    48. The answer is b.

    (Levinson, pp 221–222.) Parvovirus B19 causes the
    common disease erythema infectiosum, characterized by a “slapped cheek”
    rash. Called fifth disease, it is the fifth childhood rash disease; the other four
    are measles, rubella, scarlet fever, and roseola.






    49. The answer is c.

    (Levinson, pp 257–267.) Only two human viruses
    have been confirmed as human tumor viruses. They include human T-cell
    lymphoma/leukemia virus (HTLV) and papillomavirus. Others, such as
    EBV, HSV, and hepatitis B and C, have been implicated as tumor viruses.
    The virus that causes chicken pox (VZV) is not know to be oncogenic.





    50. The answer is e.

    (Howard, pp 781–783.) Adenoviruses are widespread
    and cause a variety of clinical problems. Many of the “viral sore
    throats” among young people living in close quarters are due to adenovirus.
    Parvovirus B19, not adenovirus, causes acute hemolytic anemia.






    51. The answer is a.

    (Davis, pp 1071–1073. Tilton, 276–278.) Although
    infection with cytomegalovirus (CMV) is common, it only rarely causes
    clinically apparent disease. Lesions characteristic of infection with CMV are
    found in up to 10% of stillborn babies; however, CMV, which can be transmitted
    transplacentally, usually is not the cause of death. Children and
    adults with immunosuppressive problems are susceptible to active disease.
    In severely immunodeficient patients such as those with AIDS, CMV ocular
    disease may occur. The patient suffers blurring of vision or vision loss,
    and ophthalmic examination reveals large yellowish-white areas with
    flame-shaped hemorrhages. Ganciclovir is now licensed for treatment of
    CMV retinitis in AIDS patients.






    52. The answer is d.

    (Levinson, pp 240–241.) Rotaviruses were initially
    identified by direct electron microscopy (EM) of duodenal mucosa of
    infants with gastroenteritis. Subsequent studies in several countries have
    shown them to be the cause of 30 to 40% of acute diarrhea in infants. They
    are non-lipid-containing RNA viruses with a double-shelled capsid.
    Although the virus has been serially propagated in human fetal intestinal
    organ cultures, cytopathic changes are minimal or absent; multiplication is
    detected by immunofluorescence. Numerous methods for rotavirus antigen
    detection, including radioimmunoassay, counterimmunoelectrophoresis,
    and enzyme-linked immunosorbent assay, have been developed and
    found to be about as effective as EM.






    53. The answer is a.

    (Levinson, pp 268–269.) SSPE is a late and rare manifestation
    of measles. It is a progressive encephalitis involving both white
    and gray matter. Demyelination is seen only at an advanced stage of the dis-
    42 Microbiology
    ease in a few cases. In 1985, viral RNA was demonstrated in brain cells
    from a patient with SSPE by the use of in situ hybridization.






    54. The answer is b.

    (Howard, pp 834–835.) Rotavirus is a viral entity
    that is similar to Nebraska calf diarrhea virus and is thought to be a major
    cause of acute diarrhea in newborn infants. Three-quarters of all adults
    have antibodies against rotavirus; passive transfer of these antibodies to the
    baby, especially through the colostrum, seems to be protective. Although
    vaccination would be expected to be of little use to the neonate, it might
    effectively immunize pregnant mothers.







    55. The answer is c.

    (Levinson, pp 226–231.) Both mumps and measles
    are well-recognized paramyxovirus infections. This group also includes
    parainfluenza virus, which causes laryngotracheobronchitis (croup) in
    children, and respiratory syncytial virus, which can cause bronchiolitis in
    infants. Paramyxoviruses have glycoprotein spikes that extend their lipid
    membrane and are responsible for hemagglutination activities.







    56. The answer is d.

    (Levinson, pp 219–220.) Papillomavirus infects the
    skin or mucosa and causes benign tumors. The lesion is termed condyloma
    acuminatum. These tumors may undergo malignant conversion and
    become squamous cell carcinomas. Classification of the human papillomavirus
    is done by DNA hybridization, and to date 46 types have been recognized.
    Some types, such as 16 and 18, are more frequently associated
    with carcinoma, while others, such as 6 and 11, are associated with benign
    tumors or warts.





    57. The answer is d.

    (Raoult, p 482.) The replication of a retroviral
    genome is dependent on the reverse transcriptase enzyme, which performs
    a variety of functions. It builds a complementary strand of DNA for the
    viral RNA template; it builds a second DNA strand complementary to the
    previous DNA; it degrades the original RNA, leaving a DNA-DNA duplex;
    and, finally, it is responsible for integrating the new viral DNA hybrid into
    the host genome.





    58. The answer is c.

    (Levinson, p 254.) St. Louis encephalitis virus has
    structural and biologic characteristics in common with other flaviviruses. It
    is the most important arboviral disease in North America. St. Louis
    encephalitis virus was first isolated from mosquitoes in California. Patients
    who contract the disease usually present with one of three clinical manifestations:
    febrile headache, aseptic meningitis, or clinical encephalitis.






    59. The answer is c.

    (Howard, pp 791–793.) (See figure below.) Presently,
    cytomegalovirus (CMV) is the most common cause of congenital and perinatal
    viral infections. Culture of the virus is a sensitive diagnostic technique;
    in the case of a neonate with classic symptoms, serum samples from
    the mother and neonate are obtained at birth. The IgM antibody titer in the
    infant’s serum should be higher than the mother’s titer, but they may be
    similar. For this reason, another sample from the infant at 1 month of age
    is tested simultaneously with the initial sample. The results should indicate
    a rise in IgM titer. Measurement of total IgM in the infant’s sera at birth is
    nonspecific and may show false-negative and false-positive reactions.







    60. The answer is c.

    (Levinson, pp 190–191.) Interferon is a protein that
    alters cell metabolism to inhibit viral replication. It induces the formation
    of a second protein that interferes with the translation of viral messenger
    RNA. Production of interferon has been demonstrated when cells in tissue
    culture are challenged with viruses, rickettsiae, endotoxin, or synthetic
    double-stranded polynucleotides. Interferon confers species-specific, not
    virus-specific, protection for cells.






    61. The answer is a.

    (Murray, p 79.) Viral cytopathic effects are thought
    to include a change in the host cell’s macromolecular synthesis and the
    structure of the cell membrane. Viruses may produce cytopathic changes
    without forming infectious virions and without replicating infectious virus,
    although the cytopathology is usually fatal to the cell. A particular cytopathic
    effect is not necessarily associated with a specific virus.






    62. The answer is a.

    (Raoult, p 356.) With an acute case of primary
    infection by Epstein-Barr virus (EBV), such as infectious mononucleosis,
    IgM antibodies to VCA should be present. Antibodies to EBNA should be
    absent, as they usually appear 2 to 3 months after onset of illness. Culture
    is not clinically useful because it (1) requires freshly fractionated cord
    blood lymphocytes, (2) takes 3 to 4 weeks for completion, and (3) is reactive
    in the majority of seropositive patients.





    63. The answer is a.

    (Raoult, pp 470–474.) While the herpesviruses
    (HSV, CMV, VZV) are all well known for latency, adenovirus can also form
    a latent infection in the lymphoid tissue. In 50 to 80% of surgically
    removed tonsils or adenoids, adenovirus can be cultured. The virus has
    also been cultured from mesenteric lymph nodes, and, in rare cases, viral
    DNA has been detected in peripheral lymphocytes. Recurrent illness usually
    does not arise from these latent infections; however, activation can
    occur in the immunosuppressed.





    64. The answer is e.

    (Raoult, p 464.) A therapeutic regimen that includes
    appropriately administered gamma globulin is effective in the treatment of
    viral hepatitis A and B. Hyperimmune rabies antiserum prolongs the incubation
    period of rabies and allows the patient more time to mount an
    immune response to the vaccine. Although it is not a primary form of treatment
    for patients with poliomyelitis, passive immunization with pooled
    gamma globulin can offer adequate protection against the disease.




    65. The answer is b.

    (Levinson, pp 214–215) Atypical lymphocytes are
    the hematologic hallmark of infectious mononucleosis with 90% or more
    of the circulating lymphocytes being atypical in some cases. These abnor-
    mal lymphocytes are not pathognomonic for infectious mononucleosis.
    They are also seen in other diseases, including cytomegalovirus infection,
    viral hepatitis, toxoplasmosis, rubella, mumps, and roseola.






    66. The answer is a.

    (Raoult, pp 284–285.) Dengue (breakbone fever) is
    caused by a group B togavirus that is transmitted by mosquitoes. The clinical
    syndrome usually consists of a mild systemic disease characterized by
    severe joint and muscle pain, headache, fever, lymphadenopathy, and a
    maculopapular rash. Hemorrhagic dengue, a more severe syndrome, may
    be prominent during some epidemics; shock and occasionally death result.





    67. The answer is b.

    (Levinson, pp 248–249.) HCV is a positive-stranded
    RNA virus, tentatively classified as a flavivirus. About half of HCV patients
    develop chronic hepatitis. A large number of infections appear among IV
    drug abusers. About 90% of the cases of transfusion-associated hepatitis
    are thought to be caused by HCV.



    68–71. The answers are 68-b, 69-d, 70-a, 71-c.

    (Levinson, pp 244–248.) Advances in the serodiagnosis of viral hepatitis have been dramatic,
    and the findings of specific viral antigens have led to further elucidation
    of the course of infections. The “Australia antigen,” discovered in
    1960, was first renamed hepatitis-associated antigen (HAA) and then,
    finally, hepatitis B surface antigen (HBsAg). It appears in the blood early
    after infection, before onset of acute illness, and persists through early convalescence.
    HBsAg usually disappears within 4 to 6 months after the start
    of clinical illness except in the case of chronic carriers.
    Hepatitis B 37 antigen (HBeAg) appears during the early acute phase
    and disappears before HBsAg is gone, although it may persist in the
    chronic carrier. Persons who are HBeAg-positive have higher titers of HBV
    and therefore are at a higher risk of transmitting the disease. HBeAg has a
    high correlation with DNA polymerase activity.
    The hepatitis B core antigen (HBcAg) is found within the nuclei of
    infected hepatocytes and not generally in the peripheral circulation except
    as an integral component of the Dane particle. The antibody to this antigen,
    anti-HBc, is present at the beginning of clinical illness. As long as there is
    ongoing HBV replication, there will be high titers of anti-HBc. During the
    early convalescent phase of an HBV infection, anti-HBc may be the only
    detectable serologic marker (window phase) if HBsAg is negative and anti-
    HBsAg has not appeared.






    72–76. The answers are 72-c, 73-e, 74-d, 75-a, 76-b.

    (Levinson, pp 232–234, 239–240, 213–214, 229–230.) The rabies virus is transmitted by
    the bite of a rabid animal. It almost always causes a fatal encephalitis if
    untreated. Postexposure treatment includes use of a killed vaccine and
    human rabies globulin (HIG). Rhinoviruses are the most prominent cause
    of the common cold. Many serotypes exist, which may account for their
    ability to cause frequent disease. Cytomegalovirus causes cytomegalic
    inclusion disease (CID), especially congenital abnormalities, in neonates.
    Malformations include microencephaly. Seizures, deafness, jaundice, and
    purpura can also occur. CID is also one of the leading causes of mental
    retardation in the United States. Respiratory syncytial virus (RSV) is the
    leading cause of pneumonia and bronchiolitis in infants. Viremia does not
    occur and treatment in several ill infants is aerosolized ribavirin. Orchitis,
    a complication of mumps virus infection in postpubertal males, can cause
    sterility if bilateral.






    77–81. The answers are 77-b, 78-c, 79-d, 80-a, 81-e.

    (Levinson, pp 197–198, 203–205.) The original vaccine for hepatitis B was prepared by
    purifying hepatitis B surface antigen (HBsAg) from healthy HBsAg-positive
    carriers and treating it with viral-inactivating agents. The second-generation
    vaccine for hepatitis B is produced by recombinant DNA in yeast cells containing
    a plasmid into which the gene for HBsAg has been incorporated.
    Influenza usually occurs in successive waves of infection with peak
    incidences during the winter months. If only minor antigenic drift is
    expected for the next influenza season, then the most recent strains of A
    and B viruses representative of the main antigens are included in the vaccine.
    Influenza vaccine consists of killed viruses.
    Live attenuated measles virus vaccine effectively prevents measles.
    Protection is provided if given before or within 2 days of exposure. Vaccination
    confers immunity for at least 15 years.
    Acyclovir is an analogue of guanosine or deoxyguanosine that strongly
    inhibits herpes simplex virus (HSV) but has little effect on other DNA
    viruses. When employed for the treatment of primary genital infection by
    HSV, both oral and intravenous formulations have reduced viral shedding
    and shortened the duration of symptoms.
    The vaccine for hepatitis A virus (HAV) is prepared from virus grown
    in culture and inactivated with formalin. Passive immunization with
    immune serum globulin confers passive protection in 90% of those
    exposed when given within 1 to 2 weeks after exposure.







    82–86. The answers are 82-c, 83-d, 84-e, 85-b, 86-a.

    (Levinson, pp 212–213, 218–219, 219–220, 214–215.) Varicella-zoster virus is a herpesvirus.
    Chickenpox is a highly contagious disease of childhood that
    occurs in the late winter and early spring. It is characterized by a generalized
    vesicular eruption with relatively insignificant systemic manifestations.
    Adenovirus has been associated with adult respiratory disease among
    newly enlisted military troops. Crowded conditions and strenuous exercise
    may account for the severe infections seen in this otherwise healthy group.
    Papillomavirus is one of two members of the family Papovaviridae,
    which includes viruses that produce human warts. These viruses are hostspecific
    and produce benign epithelial tumors that vary in location and
    clinical appearance. The warts usually occur in children and young adults
    and are limited to the skin and mucous membranes.
    Rotavirus is worldwide in distribution and has been implicated as the
    major etiologic agent of infantile gastroenteritis. Infection with this virus
    varies in its clinical presentation from asymptomatic infection to a relatively
    mild diarrhea to a severe and sometimes fatal dehydration. The exact
    mode of transmission of this infectious agent is not known. Because of
    severe side effects, the rotavirus vaccine has been recalled and is temporarily
    unavailable.
    Infectious mononucleosis caused by cytomegalovirus (CMV) is clinically
    difficult to distinguish from that caused by Epstein-Barr virus. Lymphocytosis
    is usually present with an abundance of atypical lymphocytes.
    CMV-induced mononucleosis should be considered in any case of
    mononucleosis that is heterophil-negative and in patients with fever of
    unknown origin.








    87–91. The answers are 87-c, 88-a, 89-c, 90-e, 91-b.

    (Howard, pp 791–796.) Epstein-Barr virus (EBV) is a herpesvirus that causes a number
    of syndromes; the most common is infectious mononucleosis. It is a ubiquitous
    enveloped DNA virus. Only one serotype of EBV has been recognized,
    although molecular methods have reorganized a number of
    genotypes of EBV.
    Infectious mononucleosis is an acute disease most commonly seen in
    younger people. It is characterized by a proliferation of lymphocytes,
    lymph node enlargement, pharyngitis, fatigue, and fever. Infection in
    young children is usually either asymptomatic or characteristic of an acute
    upper respiratory infection. Diagnosis is usually made by a positive het-
    erophil test. Heterophil antibodies are those that occur in one species
    (human) and react with antigens of a different species. The heterophil test
    may be insensitive (30 to 60%) in children. Definitive diagnosis is made by
    detection of antibodies to EBV components.
    EBV causes a variety of other syndromes including Burkitt’s lymphoma,
    the most common childhood cancer in Africa, and nasopharyngeal
    carcinoma, commonly seen in China.
    Similar mononucleosis-like diseases are caused by cytomegalovirus
    (CMV) and Toxoplasma gondii, a parasite. CMV causes fewer than 10% of
    infectious mononucleosis-like diseases. CMV “mono” is primarily characterized
    by fatigue. Congenital infection with CMV almost always causes
    serious sequelae, such as retardation and hearing loss. T. gondii also causes
    a variety of clinical problems, among them encephalitis in AIDS patients
    and food poisoning from the ingestion of raw meat. Although CMV and T.
    gondii are relatively rare causes of infectious mononucleosis, they must be
    ruled out, particularly when EBV tests are nonreactive.






    92–96. The answers are 92-a, 93-c, 94-e, 95-d, 96-d.

    (Howard, pp 760–762.) The diagnosis of a viral infection is made easier by the creation
    of a greater number of diagnostic virology laboratories during the past few
    decades. In order for viral diagnosis to be successful, the most appropriate
    specimen must be collected for the disease in question.
    Human papillomavirus (HPV) is often detected microscopically in cervical
    biopsies. Alternatively, there are methods to detect HPV DNA in such
    tissues as well as to serotype the virus. Evidence suggests that some HPV
    serotypes are more likely than others to cause cervical cancer.
    Many viruses have a viremic phase, but only a few, such as CMV, persist
    after the patient becomes symptomatic. CMV can be isolated from
    lymphocytes and polymorphonuclear leukocytes. This usually requires
    special separation procedures particularly in those compromised patients
    who may be neutropenic.
    Enteroviruses such as echoviruses and coxsackieviruses are the predominant
    cause of aseptic viral meningitis. While enterovirus infections are
    often diagnosed by specific antibody response, it is possible to isolate the
    virus from CSF. Herpes simplex virus (HSV) can also be isolated from CSF
    in cases of herpes encephalitis or meningitis.
    VZV and HSV are most often recovered from skin lesions, although
    varicella IgM antibody detection may be the most rapid way to diagnose
    acute VZV infection. Detection and identification of these viruses is essential
    because of the availability of antiviral agents such as acyclovir. Other
    viruses, such as enteroviruses and paramyxoviruses, cause skin lesions.
    Many viruses can be isolated from feces. Of the viral groups in these
    questions, adenovirus 40/41 is the most common stool isolate. Norwalk
    agent and other caliciviruses may also be isolated or detected from stools,
    but usually only in specialized laboratories.







    97–101. The answers are 97-e, 98-b, 99-a, 100-c, 101-d.

    (Howard, pp 833–836.) A number of viruses that cause gastroenteritis are now being recognized.
    The table on page 51 summarizes the characteristics of rotavirus,
    Norwalk virus, adenovirus, calicivirus, and astrovirus.






    102–106. The answers are 102-a, 103-c, 104-b, 105-e, 106-d.

    (Levinson, pp 244–248.) Hepatitis A virus (HAV) possesses a single-stranded
    linear RNA genome while hepatitis B virus (HBV) contains a doublestranded
    DNA genome. Detection of anti-HAV IgM in a single serum specimen
    obtained in the acute or convalescent stage is the quickest and most
    reliable method to diagnose hepatitis A infection. This antibody is usually
    present at onset of symptoms and may persist 3 to 6 months. Demonstration
    of hepatitis B surface antigen (HBsAg) in serum is the most common
    method of diagnosing HBV infection. Other serologic markers helpful in
    characterizing infection with HBV include hepatitis B surface antibody
    (anti-HBs), anti-hepatitis B core (anti-HBc), anti-hepatitis B e antigen (anti-
    HBe), and hepatitis B e antigen (HBeAg). Several epidemiologic studies
    have demonstrated that immune serum globulin (ISG) can prevent clinical
    hepatitis A even when given up to 10 days after exposure. Similar studies
    have shown that ISG was able to decrease the incidence of hepatitis B infection
    in exposed persons. Purified, noninfectious HBsAg derived from
    healthy HBsAg carriers has been used as a vaccine for active immunization
    for HBV infection. Hepatitis C is a single-stranded RNA virus belonging to
    the family Flaviviridae. The viral reservoir is human. Recent retrospective
    “lookbacks” suggest that many people were infected with HCV before testing
    of the blood supply was initiated in the early 1990s. HCV is treatable
    with combinations of drugs. The genotype of the virus plays an important
    role in the determination of length of therapy. Hepatitis D virus is an
    incomplete or defective virus which requires HBsAg as a cofactor. Both
    coinfection and secondary delta infection exist with secondary infection
    being the most serious. Hepatitis E virus is an RNA virus. Transmission is
    by the fecal-oral route although maternal-fetal transmission has recently
    been described. Prognosis is usually favorable with rare cases of fulminant
    HEV reported.






    107–110. The answers are 107-a, 108-b, 109-b, 110-c. (Levinson, pp
    181, 220.) Human papillomaviruses (HPV) are the causative agents of cutaneous
    warts as well as proliferative squamous lesions of mucosal surfaces.
    Although most infections by human papillomavirus are benign, some
    undergo malignant transformation into in situ and invasive squamous cell
    carcinoma. Both HPV and polyomavirus have icosahedral capsids and
    DNA genomes. JC virus, a polyomavirus, was first isolated from the diseased
    brain of a patient with Hodgkin’s lymphoma who was dying of progressive
    multifocal leukoencephalopathy (PML). This demyelinating
    disease occurs usually in immunosuppressed persons and is the result of
    oligodendrocyte infection by JC virus. JC virus has also been isolated from
    the urine of patients suffering from demyelinating disease. Cryotherapy
    and laser treatment are the most popular therapies for warts, although
    surgery may be indicated in some cases. At the present time, there is no
    effective antiviral therapy for treatment of infection with polyomavirus or
    HPV. West Nile virus is an arbovirus. While prevalent in Europe, Africa,
    and the Middle East, it was not seen in the United States until the summer
    of 1999. It is transmitted by mosqitoes and birds, especially crows; these
    animals are a reservoir. WNV causes a rather mild encephalitis in humans,
    the exception being older patients or those who may be immunocompromised.






    111–115. The answers are 111-b, 112-a, 113-c, 114-d, 115-e.
    (Levinson, pp 222–226.) Orthomyxoviruses and paramyxoviruses are RNA
    viruses that contain a single-stranded RNA genome. The influenza viruses
    belong to the orthomyxoviruses. They cause acute respiratory tract infections
    that usually occur in epidemics. Isolated strains of influenza virus are
    named after the virus type (influenza A, B, or C) as well as the host and
    location of initial isolation, the year of isolation, and the antigenic designation
    of the hemagglutinin and neuraminidase. Both the hemagglutinin and
    neuraminidase are glycoproteins under separate genetic control, and
    because of this they can and do vary independently. The changes in these
    antigens are responsible for the antigenic drift characteristic of these
    viruses. The paramyxoviruses include several important human pathogens
    (mumps virus, measles virus, respiratory syncytial virus, and parainfluenza
    virus). Both paramyxoviruses and orthomyxoviruses possess an RNAdependent
    RNA polymerase that is a structural component of the virion
    and produces the initial RNA. Respiratory syncytial viruses (RSV) are not
    related to the paramyxoviruses. They are 150-nm single-stranded RNA
    viruses. There are 2 antigen groups, A and B, which play no role in diagnosis
    and treatment. While the overall mortality is 0.5%, at-risk groups
    may be 25 to 35% mortality if untreated. Some parainfluenza virus infections
    (type 3) may be indistinguishable from RSV, but most parainfluenza
    infections produce a laryngotracheobronchitis known as croup.[/HIDE]
    Last edited by sunny kothiwala; 04-19-2008 at 11:12 AM.

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    ghbgfhfhfghfh


    WARNING:This is the fourth post, you are doing this! Dont spam like this anymore, Follow the RULES or you will be banned!

    -MODERATOR
    Last edited by CøMa; 05-09-2008 at 12:11 AM. Reason: warning!!

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    thanks a lot, this is a good review

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    Default thank you

    thank you
    Quote Originally Posted by sunny kothiwala View Post
    Virology
    Answers
    hidden content may not be quoted

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    Where did these questions come from: First Aid, Kaplan, etc.?

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    wow, good find I need it

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