Chapter 29: Clinical Virology Answers Explained

1. The genome of a virus is composed of: a. single-stranded DNA. b. RNA. c. double-stranded DNA. d. any of the above. D At a minimum, viruses contain a viral genome of either RNA or DNA and a protein coat—the ...

1. The genome of a virus is composed of: a. single-stranded DNA. b. RNA. c. double-stranded DNA. d. any of the above. D At a minimum, viruses contain a viral genome of either RNA or DNA and a protein coat—the capsid. The genome can be either double-stranded (ds) or single-stranded (ss). REF: 689 OBJ: Level 1: Recall 2. What requirements do viruses have for replication? a. They must be inside a living cell. b. They must be in an environment where all the necessary amino acids are present. c. They can use a dead cell to replicate. d. They need to be around dead, decaying flesh so that all the amino acids and enzymes are present. A Viruses are obligate intracellular parasites, meaning they must be inside a living cell to replicate. REF: 690 OBJ: Level 1: Recall 3. What is the correct sequence of viral infection, then destruction of a host cell? a. Attachment, penetration, replication, cell lysis b. Penetration, attachment, replication, cell lysis c. Replication, penetration, attachment, cell lysis d. Penetration, replication, attachment, cell lysis A The virus first attaches to the host cell. Next, the genome penetrates into the host cell. Once in the host cell, the virus uses the host cell machinery to replicate itself. Once replication is complete and the new viruses are assembled and ready to go, the cell is lysed to release the new viruses. REF: 690 OBJ: Level 2: Interpretation 4. When is the best time to collect a specimen for culture from a patient suspected of having a viral disease? a. 1 week after onset of symptoms b. 5 days after onset of symptoms c. Less than 3 days after onset of symptoms d. 2 weeks after onset of symptoms C Viral shedding is usually greatest during the early stages of infection, so the best specimens are those collected as early as possible. The sensitivity of viral culture may decrease rapidly 3 days after onset of symptoms. REF: 691 OBJ: Level 1: Recall 5. What is the composition of viral transport media? a. Amies media with charcoal b. Isotonic buffered saline with protein c. Cary-Blair d. Cooked meat broth B Several viral transport systems are commercially available. Most transport media consist of buffered isotonic solution with some type of protein, such as albumin, gelatin, or serum, to protect less stable viruses. REF: 691 OBJ: Level 1: Recall 6. What is an unsuitable storage temperature for viruses because it allows the development of ice crystals? a. 4 C b. –10 C c. –20 C d. –70 C C Specimens should not be stored at –20 C. This temperature facilitates the formation of ice crystals, which disrupts the host cells and results in significant loss of viral viability. REF: 691 OBJ: Level 1: Recall 7. All the following methods are used by the laboratory to diagnose viral infections except: a. chemiluminescence. b. direct detection. c. culture. d. serologic assays. A The laboratory uses three major methods to diagnose viral infections: direct detection of the virus in the clinical specimens, isolation of the virus in culture, and serologic assays to detect viral antibodies. REF: 692 OBJ: Level 1: Recall 8. Which of the following is the description of cytopathic effects in viral culture? a. The way viruses kill the infected host cell b. The visual changes produced in an infected cell by a virus c. The tears that the virus puts in an infected host cell’s membrane d. The way the virus lyses the infected cell after all the new virus particles are formed and ready to be released. B Many viruses produce characteristic visual changes in infected cells, referred to as cytopathic effect. REF: 692 OBJ: Level 1: Recall 9. All the following are direct methods for diagnosing viral infections except: a. indirect fluorescent antibody (IFA). b. direct fluorescent antibody (DFA). c. radioimmunoassay (RIA). d. enzyme immunoassay (EIA). C In DFA tests, host cells are fixed to a microscope slide and fluorescence-labeled antibodies are added. The IFA test for antigen detection can also be used. Many EIA tests for viral detection are commercially available; most are packaged as microtiter plate assays. REF: 692 OBJ: Level 1: Recall 10. All of the following methods are used as culture techniques to detect viruses except: a. cell culture. b. animal inoculation. c. embryonated eggs. d. media culture. D Traditionally, three methods are used for isolation of viruses in diagnostic virology: cell culture, animal inoculation, and embryonated eggs. REF: 693 OBJ: Level 1: Recall 11. Which of the following is the best description of a primary cell culture? a. It is a culture where tissue is removed from an animal, arranged in a monolayer, and in which very little cell division occurs. b. It is a culture that can divide, but passage is limited to 50 generations. c. It often has variable numbers of chromosomes and can be subcultured indefinitely. d. This describes the only cells the specimen will be plated on. A Primary cell cultures are obtained from tissue and removed from an animal. The tissue is finely minced and then treated with an enzyme such as trypsin to disperse further individual cells. The cells are then seeded onto a surface to form a monolayer. With primary cell lines, only minimal cell division occurs. REF: 694 OBJ: Level 1: Recall 12. Which of the following describes a diploid cell culture that is not a primary culture? a. It is a culture where tissue is removed from an animal, arranged in a monolayer, and very little cell division occurs. b. It is a culture that can divide, but passage is limited to 50 generations. c. It often has variable numbers of chromosomes and can be subcultured indefinitely. d. This describes the only cells the specimen will be plated on. B Diploid cell cultures can divide, but passage is limited to about 50 generations. With increasing passage, diploid cells become more insensitive to viral infection. REF: 694 OBJ: Level 1: Recall 13. Which of the following is the description of continuous cell cultures? a. It is a culture where tissue is removed from an animal, arranged in a monolayer, and in which very little cell division occurs. b. It is a culture that can divide, but passage is limited to 50 generations. c. It often has variable numbers of chromosomes and can be subcultured indefinitely. d. This describes the only cells the specimen will be plated on. C Continuous cell cultures have variable numbers of chromosomes and are capable of indefinite passage. Continuous cell lines are heteroploid, meaning they have an abnormal and a variable number of chromosomes that are not a multiple of the normal haploid number. REF: 694 OBJ: Level 1: Recall 14. What are giant multinucleated cells formed from cell fusion as a result of viral infection? a. Giant cells b. Macrophages c. Glial cells d. Syncytia D The respiratory viruses may not produce characteristic cytopathic effect. Respiratory syncytial virus (RSV) can produce a classic syncytial formation in Hep2 cells or even in monkey kidney cells. Syncytia are giant multinucleated cells formed from cell fusion as a result of virus infection. REF: 695 OBJ: Level 1: Recall 15. All of the following are common problems associated with using serologic methods to diagnose viral infections except: a. the host does not produce specific antibodies to viruses. b. serologic assays measure host response rather than directly detecting the virus. c. the antibody-producing capabilities of human hosts vary widely. d. the antibody level does not correlate with the activity level of the infection. A Viral serology provides limited information, and certain problems are inherent in the methods. First, serologic assays measure host response rather than directly detecting the virus. Second, the antibody-producing capabilities of human hosts vary widely and the antibody level does not necessarily correlate with the acuteness or acuity level of the infection. REF: 696 OBJ: Level 1: Recall 16. Adenoviruses produce all the following types of infections except: a. acute hemorrhagic cystitis. b. meningitis. c. acute respiratory distress. d. epidemic keratoconjunctivitis. B Although half of all adenovirus infections are asymptomatic, the virus causes about 10% of all pneumonia and 5% to 15% of all gastroenteritis in children. The virus causes upper respiratory tract infections, acute respiratory distress, epidemic keratoconjunctivitis, acute hemorrhagic cystitis, and pharyngoconjunctival fever. REF: 696 OBJ: Level 1: Recall 17. What type of genome do herpesviruses have? a. ssDNA b. ssRNA c. dsDNA d. Both dsDNA and ssRNA C The herpesviruses have a genome of linear dsDNA, an icosahedral capsid, an amorphous integument surrounding the capsid, and an outer envelope. REF: 697 OBJ: Level 1: Recall 18. What is another name for HHV-4? a. Varicella-zoster b. Cytomegalovirus c. Herpes simplex d. Epstein-Barr D Eight species of human herpesviruses (HHV) are currently known: herpes simplex virus type I (HSV-1); herpes simplex virus type 2 (HSV-2); varicella-zoster virus (VZV), also known as HHV-3; Epstein-Barr virus (EBV), also known as HHV-4; cytomegalovirus (CMV), also known as HHV-5; human herpesvirus 6 (HHV-6); human herpesvirus 7 (HHV-7); and human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma herpes virus (KSHV). REF: 697 OBJ: Level 1: Recall 19. What is another name for HHV-5? a. Varicella-zoster b. Cytomegalovirus c. Herpes simplex d. Epstein-Barr B Eight species of human herpesviruses (HHV) are currently known: herpes simplex virus type I (HSV-1); herpes simplex virus type 2 (HSV-2); varicella-zoster virus (VZV), also known as HHV-3; Epstein-Barr virus (EBV), also known as HHV-4; cytomegalovirus (CMV), also known as HHV-5; human herpesvirus 6 (HHV-6); human herpesvirus 7 (HHV-7), and human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma herpes virus (KSHV). REF: 697 OBJ: Level 1: Recall 20. What is another name for HHV-3? a. Varicella-zoster b. Cytomegalovirus c. Herpes simplex d. Epstein-Barr A Eight species of human herpesviruses (HHV) are currently known: herpes simplex virus type I (HSV-1); herpes simplex virus type 2 (HSV-2); varicella-zoster virus (VZV), also known as HHV-3; Epstein-Barr virus (EBV), also known as HHV-4; cytomegalovirus (CMV), also known as HHV-5; human herpesvirus 6 (HHV-6); human herpesvirus 7 (HHV-7), and human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma herpes virus (KSHV). REF: 697 OBJ: Level 1: Recall 21. What virus causes genital herpes? a. Human herpesvirus 6 (HHV-6) b. Cytomegalovirus (CMV) c. Herpes simplex virus type 2 (HSV-2 or HHV-2) d. Human herpesvirus (HHV-5) C Genital herpes are usually caused by HSV-2, although HSV-1 can cause as many as one third of the infections. REF: 697 OBJ: Level 1: Recall 22. A symptomatic congenital infection with cytomegalovirus (CMV) includes all the following symptoms except: a. hepatosplenomegaly. b. microcephaly. c. chorioretinitis. d. meningitis. D Congenital infections and infections in immunocompromised patients are often symptomatic and can be serious. Symptomatic congenital infection is characterized by petechiae, hepatosplenomegaly, microcephaly, and chorioretinitis. REF: 698 OBJ: Level 1: Recall 23. Complications of Epstein-Barr virus (EBV) infection include all the following except: a. acute glomerulonephritis. b. Reye’s syndrome. c. thrombocytopenia purpura with hemolytic anemia. d. splenic hemorrhage and rupture. A Complications of EBV infections are splenic hemorrhage and rupture, hepatitis, thrombocytopenia purpura with hemolytic anemia, Reye’s syndrome, encephalitis, and other neurologic syndromes. REF: 699 OBJ: Level 1: Recall 24. Which cancer is associated with Epstein-Barr virus (EBV)? a. Hepatocellular carcinoma b. Burkitt’s lymphoma c. Non-Hodgkin’s lymphoma d. T-cell leukemia B EBV has been associated with some cancers, including Burkitt’s lymphoma and nasopharyngeal carcinoma (NPC). Burkitt’s lymphoma is a malignant disease of the lymphoid tissue seen most commonly in African children. REF: 699 OBJ: Level 1: Recall 25. What disease does the varicella zoster virus (VZV) cause? a. Mumps b. Genital warts c. Chickenpox d. Rubella C VZV, in the genus Varicellovirus, spreads by droplet inhalation or direct contact with infectious lesions. The virus causes two different clinical manifestations: varicella (chickenpox) and zoster (shingles). REF: 700 OBJ: Level 1: Recall 26. What type of cancer is associated with human papilloma virus (HPV)? a. Lung b. Ovarian c. Skin d. Cervical D Although associated with the common wart, some of the HPV types are associated with cancer, including cervical cancer. REF: 701 OBJ: Level 1: Recall 27. What virus is the most common cause of viral gastroenteritis in infants and children? a. Rotavirus b. Influenzae virus c. Torovirus d. Respiratory syncytial virus (RSV) A Rotaviruses are the most common cause of viral gastroenteritis in infants and children. REF: 704 OBJ: Level 1: Recall 28. Which was the first arenavirus found to cause hemorrhagic fever? a. Ebola b. Malta c. Junin d. Marburg C The first of the arenaviruses found to cause hemorrhagic fever was the Junin virus, which causes Argentine hemorrhagic fever. REF: 704 OBJ: Level 1: Recall 29. All the following viruses cause hemorrhagic fever with renal syndrome (HFRS) except: a. Hantaan virus. b. Seoul virus. c. Dobrava virus. d. calicivirus. D The genus Hantavirus includes Hantaan virus, Seoul virus, Puumala virus, and Dobrava virus. These viruses cause a disease referred to as hemorrhagic fever with renal syndrome. REF: 705 OBJ: Level 1: Recall 30. What virus causes the Hantavirus pulmonary syndrome? a. Sin Nombre virus b. Dobrava virus c. Junin d. Lassa A The virus that occurred in mice and had infected the couple in New Mexico was ultimately characterized as a new Hantavirus; it was named Sin Nombre (“no name”) virus. The disease caused by this virus is now known as Hantavirus pulmonary syndrome. REF: 705 OBJ: Level 1: Recall 31. What virus is the most common cause of arboviral encephalitis in the world? a. Ebola b. Japanese encephalitis virus c. Venezuelan equine encephalitis virus d. Eastern equine encephalitis virus B Japanese encephalitis (JE) virus is a major cause of encephalitis in Asia and is the most common cause of arboviral encephalitis in the world. REF: 708 OBJ: Level 1: Recall 32. What is the most common flavivirus infection in the United States? a. West Nile virus b. Eastern equine encephalitis virus c. St. Louis encephalitis d. Rocky Mountain spotted fever C In the United States, the most common flavivirus is St. Louis encephalitis (SLE). Since the mid-1970s, an average of 193 cases of SLE has been reported annually in the United States. REF: 709 OBJ: Level 1: Recall 33. What virus causes the measles? a. Mumps b. Respiratory syncytial virus (RSV) c. Herpes virus 6 d. Rubeola virus D The measles virus (rubeola) is an enveloped virus classified in the genus Morbillivirus. REF: 711 OBJ: Level 1: Recall 34. What is the most common virus isolated from infants with lower respiratory infections and causes croup, bronchitis, bronchiolitis, and interstitial pneumonia? a. Respiratory syncytial virus (RSV) b. Lassa c. Rotavirus d. Norovirus A RSV is the most common virus isolated from infants with lower respiratory tract infections and causes croup, bronchitis, bronchiolitis, and interstitial pneumonia. REF: 712 OBJ: Level 2: Interpretation 35. What virus is the major cause of the common cold? a. Rotavirus b. Respiratory syncytial virus (RSV) c. Rhinovirus d. Norovirus C Rhinoviruses are the major cause of the common cold. REF: 714 OBJ: Level 1: Recall 36. What virus causes acquired immunodeficiency syndrome (AIDS)? a. Hepatitis C virus (HCV) b. Hepatitis B virus (HBV) c. Respiratory syncytial virus (RSV) d. Human immunodeficiency virus (HIV) D HIV causes AIDS. REF: 714 OBJ: Level 1: Recall 37. What viral genus causes rabies? a. Lyssavirus b. Lassa virus c. Marburg virus d. Calicivirus A Rabies is caused by several strains of viruses belonging to the genus Lyssavirus. REF: 716 OBJ: Level 1: Recall 38. Which virus is a bloodborne pathogen? a. Hepatitis A virus (HAV) b. Rabies c. Hepatitis C virus (HCV) d. Norovirus C Hepatitis C is spread through blood and blood products. REF: 693 OBJ: Level 1: Recall 39. What is a prion? a. A virion b. A viroid c. A proteinaceous infectious particle d. A lipopolysaccharide infectious particle C Prions, proteinaceous infectious particles, cause a group of diseases in mammals called transmissible spongiform encephalopathies. REF: 723 OBJ: Level 1: Recall 40. What infectious agent causes Creutzfeldt-Jakob disease, Kuru, and “mad cow” disease? a. Prion b. Bacteria c. Virus d. Parasite A Prions, proteinaceous infectious particles, cause a group of disease in mammals called transmissible spongiform encephalopathies (TSEs). Examples of TSEs include Kuru and Creutzfeldt-Jakob disease in humans, scrapie in sheep, bovine spongiform encephalopathy (BSE, or mad cow disease) in cattle, and chronic wasting disease in elk. REF: 723 OBJ: Level 2: Interpretation