MLT GlobeVirology: Arboviruses & zoonotic viruses
28 Virology MCQs on Arboviruses & zoonotic viruses with answers and explanations.
The human diploid cell vaccine (HDCV), grown in fibroblasts and inactivated, is used before and after exposure to prevent which disease?
HDCV is an inactivated rabies vaccine given as pre-exposure and post-exposure prophylaxis. Yellow fever and varicella vaccines are live attenuated.
The term "arbovirus" describes viruses grouped by which shared feature?
Arboviruses (arthropod-borne) are carried by mosquitoes, ticks or sandflies, e.g. dengue and West Nile viruses. HIV, influenza and rhinovirus spread without vectors.
A brain biopsy shows eosinophilic cytoplasmic inclusions in hippocampal and Purkinje neurons. Which infection is indicated?
Negri bodies are cytoplasmic inclusions of rabies virus nucleocapsid in neurons, especially hippocampal pyramidal and cerebellar Purkinje cells.
Urban yellow fever passes from person to person through which vector?
In the urban cycle, Aedes aegypti transmits yellow fever between humans. Anopheles transmits malaria.
A traveller returns from South Asia with sudden high fever, retro-orbital pain, severe muscle and joint pain, a rash and low platelets. Which infection is most likely?
Dengue ("breakbone fever") causes fever, headache, retro-orbital pain, myalgia, arthralgia, rash, leukopenia and thrombocytopenia. NS1 antigen or RT-PCR confirms early infection.
Which of these viruses causes an almost uniformly fatal encephalitis that can be prevented by timely vaccination even after exposure?
Symptomatic rabies is nearly always fatal, but the long incubation allows post-exposure vaccine plus rabies immune globulin to prevent disease.
In the jungle (sylvatic) cycle of yellow fever in Africa and South America, which animals are the main reservoir?
Sylvatic yellow fever circulates between monkeys and tree-hole mosquitoes; humans entering the forest are infected incidentally.
Medically important arboviruses mostly belong to togaviruses, bunyaviruses and which other family?
Flaviviruses (dengue, Zika, yellow fever, West Nile) are a major arbovirus group, alongside alphaviruses (Togaviridae) and bunyaviruses such as CCHF virus.
A horse and its owner both develop encephalitis in late summer; dead crows were found nearby. Which mosquito-borne flavivirus is suspected?
West Nile virus is maintained in birds, spread by Culex mosquitoes and infects humans and horses as dead-end hosts. Bird die-offs often signal activity.
Which infection is transmitted by the day-biting Aedes aegypti mosquito?
Aedes aegypti transmits dengue, as well as Zika, chikungunya and yellow fever. Malaria is spread by Anopheles, CCHF by Hyalomma ticks, and brucellosis (Malta fever) through animal products.
Dengue, Zika and chikungunya viruses are mainly transmitted by which vector?
Aedes aegypti (and Aedes albopictus) spread all three viruses. Culex mosquitoes mainly spread West Nile and Japanese encephalitis viruses.
Japanese encephalitis virus is transmitted to humans mainly by:
Culex mosquitoes breeding in rice fields transmit JE virus between pigs, water birds and humans.
Chikungunya fever is characterised especially by:
The name comes from a Makonde word for 'that which bends up', reflecting the disabling arthralgia.
Which disease is caused by an alphavirus (family Togaviridae)?
Alphaviruses include WEE, EEE and chikungunya viruses. Dengue and yellow fever are flaviviruses; Marburg is a filovirus.
Which statement best describes hantavirus pulmonary syndrome?
After a febrile prodrome, capillary leak causes rapid pulmonary oedema and shock. It is acquired by inhaling rodent (deer mouse) excreta; treatment is supportive.
Specimens from a suspected Ebola virus disease patient need which biosafety containment for virus culture?
Ebola is a risk group 4 filovirus; culture is limited to BSL-4 laboratories. Routine clinical tests are done with enhanced precautions after risk assessment.
Which description fits Ebola virus?
Ebola is a filamentous, enveloped filovirus with a non-segmented negative-sense ssRNA genome.
Which test on post-mortem brain tissue is the reference standard for diagnosing rabies?
WHO and OIE regard DFA on brain tissue (brainstem, cerebellum) as the gold standard; Negri bodies on histology are absent in many cases.
A hiker bitten by an Ixodes tick in a forest of central Europe develops meningoencephalitis. The same vector also carries Babesia and Anaplasma. The likely virus is:
Ixodes ticks transmit tick-borne encephalitis virus, a flavivirus, as well as Babesia and anaplasmosis/ehrlichiosis agents. West Nile and dengue are mosquito-borne.
A patient has had fever, headache and muscle pain for 2 days after travel to a dengue area. Which test is most useful now?
During the first 5 days of fever, viremia and NS1 antigen are high while IgM is usually not yet present. IgM becomes useful after about day 5.