Yellow fever infections are on the rise in several Americas countries, with the virus expanding its reach outside the zone where cases are typically reported, the Pan American Health Organization (PAHO) said yesterday in an epidemiologic alert. PAHO is one of the regional offices of the World Health Organization (WHO).

The increased cases began at the end of 2024 and continued into the first weeks of 2025, with 61 cases reported in 2024, 30 of them fatal. The number exceeds the total of both 2022 and 2023 for Bolivia, Brazil, Colombia, and Peru. In January, the region reported 17 more cases, 7 of them fatal.
PAHO said that, in 2024, cases were mainly reported from the Amazon region of Bolivia, Brazil, Colombia, Guyana, and Peru. The disease has now started spreading outside the zone, however, especially in Brazil's Sao Paulo state and Colombia's Tolima department. Peru has reported a death from yellow fever, and PAHO warned that other countries could be affected.
Most cases involved unvaccinated people
Officials said most of the 2024 cases occurred in people who weren't vaccinated, and they urged countries to strengthen their vaccination programs and to take steps to inform people who are traveling to high-risk areas.
With the change in transmission pattern, PAHO urged countries in areas near affected zones to step up surveillance to quickly detect suspected cases and isolate and treat affected patients.