The 2015-2016 Zika virus epidemic, linked to devastating birth defects, prompted WHO’s second Public Health Emergency declaration and changed pregnancy advice worldwide.

The Outbreak

Zika virus, transmitted by Aedes mosquitoes, exploded across Brazil in 2015 before spreading to 86 countries in the Americas, Africa, and Asia. Most infections caused mild symptoms - fever, rash, joint pain - or no symptoms at all. But pregnant women faced horrifying risks.

Microcephaly Crisis

Brazilian doctors noticed a surge in microcephaly - babies born with abnormally small heads and severe brain damage. By early 2016, over 4,000 suspected cases emerged. Research confirmed Zika crossed the placenta, attacking fetal brain cells during development. Pregnancy became terrifying for millions.

Global Response

WHO declared a Public Health Emergency in February 2016 (only the fourth in history after H1N1, polio, and Ebola). Countries urged women to delay pregnancy. The 2016 Rio Olympics faced calls for postponement. Athletes, including basketball star Stephen Curry, considered boycotting.

Transmission

Beyond mosquitoes, Zika spreads sexually - the virus persists in semen for months. Public health guidance recommended condoms and abstinence. Blood banks implemented screening. The complexity of transmission made containment difficult.

The Decline

By late 2017, cases plummeted - likely due to population immunity after widespread infection. But the virus persists in endemic regions. An estimated 5-10% of babies born to infected mothers suffer Congenital Zika Syndrome - microcephaly, seizures, vision problems, developmental delays.

Vaccine Development

Several Zika vaccine candidates entered trials but stalled as the epidemic waned - pharmaceutical companies lost financial incentive. The pattern repeated with Ebola and later COVID-19: emergency funding during crises, abandonment when headlines fade.

Source: CDC Zika Virus