PAHO Warns of Rising Yellow Fever Cases in the Americas

The Pan American Health Organization (PAHO) issued an epidemiological alert following a significant increase in yellow fever cases across the Americas in early 2025. As of March 22, 2025, confirmed human cases more than doubled the total reported in 2024, raising concerns about the potential spread of the disease.

In the first three months of 2025, 131 cases of yellow fever and 53 deaths were confirmed. This contrasts with 2024, when 61 cases and 30 fatalities were reported throughout the entire year. Cases have been identified in Bolivia, Brazil, Colombia, and Peru. Some infections have been recorded outside the Amazon region, which is traditionally affected by the virus.

Colombia's Tolima department has reported new cases since October 2024, marking the virus' emergence in previously unaffected areas. Agricultural work in these zones presents an increased risk of exposure. The expansion of new cases underscores the need for strengthened surveillance, prevention, and control measures.

In Brazil, São Paulo has reported 34 cases and 19 deaths. Its proximity to densely populated urban centers raises concerns about a wider outbreak.

Yellow fever is a severe viral disease transmitted by mosquitoes and can be fatal. However, it is preventable through vaccination. Most cases detected involved unvaccinated individuals. On March 27, PAHO urged countries to intensify vaccination efforts in at-risk areas, aiming for coverage above 95%. The agency also recommended reviewing vaccine stockpiles, establishing rapid outbreak response plans, and ensuring travelers to endemic areas are informed and vaccinated.

Since Brazil's 2016-2018 yellow fever epidemic, the disease has remained a public health concern in the Americas. The virus circulates in a sylvatic cycle among specific mosquito species and non-human primates across 13 countries and territories. Since 1960, the region has recorded 9,591 human cases and 3,444 deaths.

In February, PAHO assessed the risk of yellow fever outbreaks as high, following the increase in cases in late 2024 and early 2025. The organization continues to monitor the situation and support countries in adopting effective surveillance, prevention, and control strategies.