7. Which of the following viruses has been linked to microcephaly?
a. Yellow fever
b. Zika
c. Dengue
d. Japanese encephalitis
Zika virus is the one linked to microcephaly among the options. This flavivirus, transmitted primarily by Aedes mosquitoes, causes severe congenital malformations when pregnant women are infected.
Correct Answer
The correct choice is b. Zika. During the 2015-2016 outbreaks in Brazil and other regions, Zika virus infection in pregnancy led to a sharp rise in microcephaly cases, where infants are born with abnormally small heads due to impaired brain development. The virus crosses the placenta, targets neural progenitor cells, triggers cell death, and disrupts cortex formation.
Option Analysis
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a. Yellow fever: This flavivirus causes hemorrhagic fever but shows no direct causal link to microcephaly. Some studies note potential protective effects from yellow fever vaccination against Zika-related microcephaly due to cross-immunity, not causation.
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b. Zika: Established cause; prenatal infection reduces neuron production, leading to smaller brains and microcephaly as part of congenital Zika syndrome.
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c. Dengue: Another flavivirus that may worsen Zika outcomes via antibody-dependent enhancement in co-exposed pregnancies, but dengue alone does not cause microcephaly.
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d. Japanese encephalitis: Targets the brain causing encephalitis with inflammation and neuronal damage, primarily postnatally; animal studies show fetal deaths but no microcephaly.
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