A pregnant woman returns from a region with Zika virus transmission. How is Zika mainly transmitted, and what is the key fetal concern?

Answer: D. Bite of an infected Aedes mosquito (also sexual transmission); the key fetal concern is microcephaly and brain abnormalities

Zika virus in pregnancy

Zika virus is predominantly transmitted by the bite of an infected female Aedes mosquito, and also by sexual transmission.

Clinical course and fetal risk

• Symptoms develop in ~3-12 days (often mild or asymptomatic).
• About 10% of fetuses infected with Zika will have long-term effects.
• The key fetal concern is microcephaly and brain abnormalities (e.g. microencephaly, agyria), with intrauterine growth restriction and oligohydramnios.

Why D

Zika is mosquito-borne (and sexually transmitted), with microcephaly/brain abnormalities the major fetal concern.

Why the others are wrong

Zika is not transmitted by ticks, food, respiratory droplets, or blood transfusion alone; fetal anaemia (parvovirus), deafness (CMV/rubella), cardiac defects (rubella) and limb hypoplasia (varicella) are features of other infections - the hallmark of Zika is microcephaly.