Zika

Primarily by daytime-biting Aedes mosquitoes (the same species that spread dengue and chikungunya). Also transmitted sexually (in semen and vaginal fluids for weeks to months after infection) and from mother to fetus during pregnancy.

Symptoms

Asymptomatic in around 80% of infections. When symptomatic: low-grade fever, maculopapular rash, conjunctivitis, joint and muscle pain, headache. Mild and self-limiting in adults. Very rarely associated with Guillain-Barré syndrome. The major risk is congenital Zika syndrome in fetuses of infected pregnant women.

Treatment

No specific antiviral treatment. Supportive care: rest, fluids, paracetamol. Avoid aspirin and NSAIDs until dengue has been excluded. Pregnant women diagnosed with Zika need specialist obstetric follow-up with serial fetal ultrasounds.

Endemic regions

Most of the Americas (especially Caribbean, Central America, northern South America), parts of Southeast Asia, the Pacific Islands, and sub-Saharan Africa. Outbreak intensity varies year to year; CDC and ECDC maintain country-level current-risk maps. Zika has been documented sporadically in southern Europe via local Aedes albopictus populations.

Prevention & prophylaxis

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Daytime mosquito protection

Aedes mosquitoes bite mainly during the day, with peaks in early morning and late afternoon. Apply DEET 20–50% or Picaridin 20% to all exposed skin. Wear long sleeves and trousers. Stay in air-conditioned or well-screened accommodation. Same precautions as for dengue and chikungunya — they share the vector.

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Pregnancy and conception planning

Pregnant women should NOT travel to areas with current Zika transmission — congenital Zika syndrome can cause microcephaly and severe brain abnormalities. Couples planning conception: women with possible exposure should wait at least 2 months before trying to conceive; men with possible exposure should wait at least 3 months and use condoms with partners who could become pregnant during that window. Discuss any Zika-area travel during the periconception period with a travel medicine specialist.

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Sexual transmission prevention

Use condoms or abstain from sex during travel and for 3 months after return from a Zika area, even if asymptomatic. This applies regardless of pregnancy plans — sexual transmission has been documented for both male-to-female and female-to-male partners.

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Symptoms after travel

Most Zika infections (~80%) cause no symptoms at all. When present, symptoms are usually mild: low-grade fever, maculopapular rash, non-purulent conjunctivitis, joint pain — lasting 2–7 days. Use paracetamol; avoid aspirin and NSAIDs until dengue is ruled out. Seek testing if symptomatic during or shortly after travel and you are pregnant or considering pregnancy.