Arbovirus Test

Questions on viral zoonoses and arboviruses. Answers are in bold 1. You are practicing medicine in Mississippi and one of your patients wishing to see something higher than Woodall Mountain (806 feet) spends her summer vacation hiking in the Grand Tetons (Wyoming). A few days after her return home, she complains of fever, headache, muscle and joint pain. Which of the following viral diseases might be the most likely cause? A. St. Louis Encephalitis virus B. Kern Canyon virus C. LaCrosse virus D. Colorado Tick Fever virus E. Coxsackie virus A14 2. Concerning rabies virus, which of the following statements is correct? A. A bite from an infected animal invariable results in a fatal case of rabies encephalitis. B. The virus enters the CNS by crossing the blood brain barrier. C. Recommended post-exposure rabies prophylaxis requires only that the rabies vaccine (HDCV) be administered. D. In about 20% of human cases, paralysis and coma follow the prodrome thus bypassing the "sensory excitation phase". E. None of the above. 3. St. Louis Encephalitis virus infections A. causes most severe disease in young patients. B. can be treated with ribavirin. C. Both A and B. D. Neither A nor B. 4. Arenaviruses are transmitted by A. the bites of infected animals. B. ticks and other biting insects. C. contact with the excretions and secretions of infected rodents. D. infected blood products. E. None of the above. 5. With reference to illnesses caused by "arboviruses", which of the following statements is correct? A. Effective vaccines exist to prevent most serious infections. B. Phosphonecrotic acid has broad-spectrum antiviral effect and is clinically useful against these viruses. C. A single serum sample taken at the time of presentation is sufficient to make an accurate diagnosis. D. Eastern Equine Encephalitis infects many patients, but few show clinical disease. E. None of the above. 6 Dengue Shock Syndrome is due to A. a highly virulent strain of Dengue 4 B. infection of an immunocompromised host C. infection in elderly patients D. the presence of non-neutralizing antibody in a young patient infected with a heterologous subtype of Dengue. E. none of the above 7. In September of 1996, your patient, a 55 year old man in otherwise good health, presents with severe headache, fever, and a stiff neck. Within a few days he develops symptoms consistent with encephalitis. Subsequently, his illness worsens and he dies. His medical history shows that he worked extensively outdoors, but that he did not travel far from the Jackson area. In considering a possible viral etiology for his illness, which virus should be viewed as a most likely causative agent. A. Colorado Tick Fever virus B. California encephalitis virus C. St. Louis encephalitis virus D. Herpes simplex virus type 1 E. Eastern Equine Encephalitis virus 8. Standard treatment for the bite of an animal suspected to be rabid includes A. prompt and aggressive first aid (i.e. cleaning the wound) B. administration of human anti-rabies immunoglobulin C. vaccination with the human diploid cell vaccine D. none of the above E. all of the above 9. Which one of the following viruses is LEAST likely to be transmitted by an arthropod vector? A. Togaviruses B. Flaviviruses C. Powassan virus D. St. Louis encephalitis E. Hantaan virus 410. A child reports to you with obvious signs of encephalitis which progresses to coma and death. The child lives near a swamp. There have been several other cases of encephalitis in this area in recent weeks as well as unexplained horse and pheasant deaths. Which is the most likely viral cause of this illness? A. Herpes simplex virus B. Dengue type 4 C. Human immunodeficiency virus D. Eastern equine encephalitis E. St. Louis encephalitis 11. Which statement pertaining to Togaviruses is INCORRECT? A. They are enveloped. B. They express a subgenomic mRNA. C. They have viral glycoproteins embedded in their envelope. D. They contain three single stranded RNA genome segments of negative polarity. E. They can be transmitted by arthropod vectors. 12 Which statement pertaining to Hantaviruses is CORRECT? A. They are readily transmissible from human to human. B. They are not associated with renal failure. C. They are transmitted by infected rodent feces and urine. D. They have not been found in rats. E. They are present in 10% of bats. 13. All of the following statements concerning rabies are true EXCEPT A. bats harbor rabies but show no symptoms. B. aggressive cleansing of a rabid animal bite is of little value because the virus enters the nerve cells. C. rabies has a very wide host range in nature. D. rodents are not a significant reservoir of rabies. E. rabies is a zoonosis. 14. Which one of the following is most likely to be transmitted by a tick? A. Arenaviruses. B. Connecticut tick fever virus. C. Powassan virus. D. St. Louis encephalitis virus. E. Hantaan virus. 15. Human viral zoonoses are present in all of the following families EXCEPT: A. Arenaviridae. B. Bunyaviridae. C. Rhabdoviridae. D. Flaviviridae. E. Filoviridae. 16. All of the following statements pertaining to Arenaviruses are true EXCEPT: A. They are enveloped. B. They can be transmitted in the feces and urine of infected rodents. C. They have viral glycoproteins embedded in their envelope. D. They contain two single-stranded RNA genome segments of negative polarity. E. They have a nucleocapsid structure with protruding fibers that looks like a satellite or a World War Two mine. 17. All of the following statements pertaining to Hantaviruses are correct EXCEPT: A. They are not readily transmissible from human to human. B. They are present in 10% of bats. C. They are transmitted in the feces and urine of infected rodents. D. They are associated with renal failure. E. Korean Hemorrhagic fever is caused by the Hantaan Hantavirus. 18. Which of the following statements concerning rabies is correct? A. Rats harbor rabies but shown no symptoms. B. Aggressive cleansing of a rabid animal bite is of little value because the virus enters nerve cells quickly. C. It is caused by a bullet shaped virus. D. Rodents are significant reservoirs of rabies. E. Rabies has a very narrow host range in nature. 19. Which one of the following statements BEST describes BOTH the Bunyaviridae and the Arenaviridae? A. They are usually transmitted by insect vectors. B. They are non-enveloped. C. They are a major cause of pediatric encephalitis in the U.S. D. They contain multi-segmented, single stranded RNA genomes. E. They are commonly associated with renal syndromes. 91% answered correctly; answer and explanation 20. Which one of the following families of viruses does NOT contain an arbovirus which is active in the U.S. ? A. Bunyaviridae B. Reoviridae C. Togaviridae D. Filoviridae E. Flaviviridae 97% answered correctly, answer and explanation 21. Which one of the following virus / natural host pairs is WRONG? A. St. Louis Encephalitis / birds B. Eastern equine encephalitis / horses C. Arenaviruses / rodents D. Rabies / bats E. California encephalitis / small mammals 73% answered correctly, answer and explanation 22. Which one of the following statements concerning virus transmission is CORRECT? A. Hantaviruses are normally transmitted by an animal bite. B. Powassan encephalitis is transmitted by a mosquito vector. C. Western equine encephalitis is transmitted by a tick vector. D. Rabies is transmitted by aerosols of rodent excretions. E. Ebola is transmitted from human to human by bodily fluids. 88% answered correctly, answer and explanation 23. The average incubation period for rabies is six days. The natural host of the Ebola virus is thought to be the monkey. A. Both statements are TRUE. B. Both statements are FALSE. C. The first statement is TRUE, the second statement is FALSE. D. The first statement is FALSE, the second statement is TRUE. 23% answered correctly, answer and explanation 24. Which one of the following statements concerning rabies is CORRECT? A. There is an extensive viremia during disease progression. B. Rodents are a common reservoir of rabies. C. It is a Rhabdovirus with a multi-segmented RNA genome. D. It can occur as two distinct clinical forms: dumb or furious E. Rabies has been demonstrated in raccoons and skunks in Mississippi since 1990. 31% answered correctly, answer and explanation 25. The culturing of Epstein-Barr virus (EBV) from throat washes is useful during diagnosis of infectious mononucleosis. 90% of acute EBV patients are positive for heterophile antibody. A. Both statements are TRUE. B. Both statements are FALSE. C. The first statement is TRUE, the second statement is FALSE. D. The first statement is FALSE, the second statement is TRUE. 16% answered correctly, answer and explanation 26. Which one of the following statements is CORRECT? A. Aseptic meningitis occurs in the majority of primary genital herpes infections. B. Acyclovir is the antiviral agent that can be used to suppress recurrent HSV infections. C. Recurrences of genital herpes are usually more severe than the primary infection. D. HSV-1 is more frequently associated with genital herpes than HSV-2. E. Herpetic encephalitis is usually caused by HSV-2. 94% answered correctly, answer and explanation 19. The correct answer is D. The Bunyaviridae contain three single stranded RNA genome segments and the Arenaviridae contain two. A. The Arenaviridae are viral zoonoses and are transmitted by aerosols of infected rodent excretions or secretions not by insect vectors. B. Both viruses are enveloped. C. California encephalitis (Lacrosse virus) is a Bunyavirus which is the major cause of pediatric encephalitis in the U.S. E. The Hantavirues which are members of the Bunyaviridae have been commonly associated with renal syndromes but the Arenaviruses have not, in fact the Arenaviruses are usually associated with fevers including hemorrhagic fevers such as Junii and Machupo. 20. The correct answer is D. The Filoviruses include Ebola and Marburg these are viral zoonoses which have not been shown to be transmitted by insect vectors but which can be transmitted from human to human by infected bodily fluids. The four virus families that contain arbo viruses (Better Remember These Four) are Bunyaviridae, Reoviridae, Togaviridae and Flaviridae. 21. The correct answer is B. Horses are a dead-end hosts for EEE because levels of viremia are not sufficient to result in horse to vector transmission. The natural hosts for EEE are birds that nest in swampy areas. The natural host for a virus is the organism that harbors the virus in the wild. Most natural hosts do not show symptoms of disease and can become chronic carriers of the virus. But care must be taken not to overgeneralize because some creatures that are considered natural hosts do show symptoms; for example raccoons and rabies, or humans and measles or humans and YF. 22. The correct answer is E. Although there is evidence for aerosol transmission of Ebola in caged monkey colonies there is no evidence that it is transmitted by aerosol in humans. Contact with bodily fluids of infected patients is the major risk of infection. These is particularly acute for relatives and hospital staff who come in contact with the infected patient. Hantaviruses are transmitted by aerosols of infected rodent urine or fesces. Powassan is transmitted by the tick; WEE is transmitted by the mosquito, and rabies is transmitted by the bite or scratch of an infected animal. 23. The correct answer is B, both statements are false. The low percentage of the class who answered this question correctly (23%) led to the exclusion of this question from the grade average. Statement 1: The incubation period for rabies ranges from 6 days to one year, but the average is 5 weeks. This long incubation time permits the vaccine to be given and immunity to be generated even after the virus has been transmitted. Statement2: The natural host or reservoir for Ebola has not been determined. Many monkey species are rapidly killed by the virus, for example ebola has almost 100% mortality in chimpanzees. The possibility that this virus is found in insects or in plants is also being considered. 24. The correct answer is D. Their are two clinical presentations of rabies in humans, classical also known as furious and dumb (paralytic symptoms). A. Rabies is an acute encephalitis and in humans there is no viremia. In fact it has been shown that in infected animals severing the nerves leading to the salivary glands can prevent infection of these glands. B. Rodents are not a significant source of rabies and individuals who have been bitten by a rodent are not at risk for rabies. C. Rabies is a Rhabdovirus but this family contains a ssRNA genome which is NOT segmented. E. Cases of rabies in terrestrial animals have not been seen in Mississippi in over 30 years but 10% of bats in Mississippi are positive for rabies. 25. The correct answer is D. Only 16% of the class chose the correct answer, this question was tossed. The question was based on the virology case studies that were presented to the class. EBV is a herpesvirus which can remain latent in B lymphocytes. Most adults are positive for the virus, and EBV is normally shed into the saliva in virus positive individuals, therefore culturing of the virus is not useful in diagnosis, Statement is False. Heterophile antibody is a classic indicator of infectious mononucleosis (that is primary EBV infection). 90% of mononucleosis patients are positive for heterophile antibody. Statement 2 is true. 26. The correct answer is B. Acyclovir is routinely used to treat HSV infections. This question was also based on the virology case studies. A. Aseptic meningitis occurs is less than one third of primary genital herpes infections. C. Recurrences of genital herpes are usually milder and some infected individuals never get recurrent lesions. D.HSV-2 is most commonly associated with genital herpes and HSV-1 with oral herpes lesions. E. Most cases of herpetic encephalitis are caused by HSV-1. Back to the Rays Virology Home Page Please Send Any Comments Or Suggestions To The PageWeaver