Yellow Fever Risk Remains High as Cases Rise Sharply in 2025

The Pan American Health Organization (PAHO) has issued a new Rapid Risk Assessment warning that yellow fever remains a significant public health threat in the Americas, including the Caribbean. So far in 2025, 221 confirmed cases and 89 deaths have been reported—an eightfold increase compared to the same period in 2024.

The surge is attributed to the reactivation of sylvatic (jungle) transmission cycles, with spillover into human populations, especially among the unvaccinated. Most recent cases have occurred outside traditional zones, including São Paulo State in Brazil and Tolima Department in Colombia, increasing the risk of potential urban outbreaks.

Vaccination coverage has declined in many endemic countries, with 10 of 12 falling below the 95% target. Though vaccination efforts are improving, global vaccine supply remains limited.

PAHO urges strengthened surveillance, targeted vaccination, and improved public health communication. It is also assisting countries with strategies such as using fractional doses and focusing on high-risk populations.

Yellow fever, transmitted by sylvatic mosquitoes, causes symptoms ranging from fever and muscle pain to, in severe cases, organ failure and death. PAHO continues to monitor developments and provide support for outbreak prevention.