What Is Zika Virus?

Zika virus is a mosquito-borne flavivirus transmitted by Aedes aegypti and Aedes albopictus mosquitoes. It is also sexually transmissible. The virus causes a mild, self-limiting illness in most adults (about 80% of infections cause no symptoms). However, Zika poses a serious threat in pregnancy: infection in the first trimester is associated with Congenital Zika Syndrome (CZS), which includes microcephaly, severe brain malformations, and other neurological abnormalities. The 2015–2016 epidemic in the Americas — centered in Brazil — infected an estimated 1.5 million people and caused thousands of CZS cases, triggering a WHO Public Health Emergency of International Concern.

Zika affects two groups very differently:

Non-pregnant adults: Low-risk — most infections are asymptomatic or cause 3–7 days of mild fever, rash, joint pain, and conjunctivitis. Serious complications (Guillain-Barré Syndrome, meningoencephalitis) occur in a small minority.
Pregnant women and their fetuses: High stakes. First-trimester infection carries approximately 6–12% risk of Congenital Zika Syndrome. Even second and third trimester infections can cause placental damage. Children born with CZS may have microcephaly, cortical blindness, hearing loss, seizures, and developmental delays requiring lifelong care.

Zika spreads through:

Mosquito bites: Primary route — Aedes aegypti (daytime biting) and Ae. albopictus in tropical/subtropical regions
Sexual contact: Zika can survive in semen for up to 3 months after infection; in vaginal secretions for shorter periods. Both male-to-female and female-to-male transmission documented.
Mother to fetus: During pregnancy (primary concern)
Blood transfusion: Documented; blood banks screen donors in endemic areas

For pregnant women or those trying to conceive:

Avoid travel to active Zika transmission areas if possible
If travel unavoidable: use DEET repellent consistently, wear long-sleeved clothing, use air conditioning or nets
Use condoms throughout pregnancy if partner has traveled to Zika-active area
Get tested after possible exposure — RT-PCR within 14 days, IgM serology after 2 weeks

For all travelers: DEET repellent, long clothing, mosquito nets; use condoms for 3 months (men) or 2 months (women) after return from Zika-active areas.

Is Zika still active in 2025?: Zika is no longer causing epidemic waves in the Americas but remains endemic in tropical regions of Latin America, Southeast Asia, and parts of Africa. Low-level transmission continues in Brazil, Colombia, and Southeast Asian countries. WHO surveillance detected Zika activity in 89 countries as of 2024. Risk is highest during rainy seasons when mosquito populations peak. Pregnant travelers should check WHO travel advisories before visiting any tropical destination.
How long does Zika stay in the body?: Zika RNA is detectable in blood for approximately 1–2 weeks after infection. In urine, it can persist slightly longer (2–3 weeks). In semen, Zika RNA has been detected for up to 3 months (longest documented: 181 days). In saliva, it is detectable for about 1 week. These timelines inform the 3-month (men) and 2-month (women) wait recommendations before attempting conception after exposure.
What is Guillain-Barré Syndrome (GBS) in Zika?: GBS is a rare autoimmune condition where the immune system attacks peripheral nerves, causing ascending weakness and paralysis. Zika triggers GBS in approximately 1 in 4,000 infections — making it the first virus confirmed to cause GBS at population scale. Most Zika-GBS patients recover full function within 6–12 months with IVIG or plasmapheresis treatment. About 5% require mechanical ventilation for respiratory failure.