MLT GlobeVirology: Arboviruses & zoonotic viruses – page 2
28 Virology MCQs on Arboviruses & zoonotic viruses with answers and explanations.
Which laboratory change in dengue warns of plasma leakage and possible severe disease?
Plasma leakage concentrates the blood, so hematocrit rises while platelets fall quickly. WHO lists this combination as a warning sign.
A patient with encephalitis in summer is suspected of West Nile virus infection. Which test is most useful?
IgM does not cross an intact blood–brain barrier, so WNV IgM in CSF shows central nervous system infection. Viremia is short, so culture and PCR are often negative.
A livestock worker in Pakistan has fever and bleeding after a tick bite. Crimean-Congo hemorrhagic fever is suspected. What is the key laboratory precaution?
CCHF virus spreads through blood and body fluids and is a risk group 4 pathogen. Samples need strict precautions, and culture is done only in maximum containment laboratories.
Puumala virus, a cause of haemorrhagic fever with renal syndrome in Europe, belongs to which genus?
Puumala virus is a rodent-borne orthohantavirus (family Hantaviridae, order Bunyavirales). Nairoviruses include CCHF virus; phleboviruses include sandfly fever viruses.
Cache Valley virus, an orthobunyavirus causing birth defects in sheep and rare human infection, is transmitted by which vectors?
Cache Valley virus is carried by several mosquito genera, including Aedes, Anopheles and Culiseta. Ticks, sandflies and fleas are not its vectors.
On day 3 of illness, a dengue patient has high dengue IgG, and IgM is low or absent. This pattern suggests:
In secondary infection, IgG rises rapidly and early while IgM is low. Secondary infection with a different serotype has higher risk of severe dengue due to antibody-dependent enhancement.
A traveller has positive IgM for both dengue and Zika viruses. Which test best identifies the infecting flavivirus?
Flavivirus antibodies cross-react in ELISA. PRNT measures virus-specific neutralizing antibodies and is used to separate dengue from Zika.
Which set of specimens is used for ante-mortem laboratory diagnosis of human rabies?
No single ante-mortem test is sensitive, so saliva and skin biopsy (RT-PCR, antigen detection) are tested with serum and CSF antibodies. Brain tissue is used after death.