The Pan American Health Organization (PAHO) has issued a new Rapid Risk Assessment (RRA) highlighting a sharp increase in yellow fever cases across the Americas, warning that the public health threat remains high in 2025.
According to the report, released on May 23, confirmed human cases of yellow fever have surged to 221 so far this year—more than eight times the number reported during the same period in 2024. The outbreak has also claimed 89 lives. For comparison, the entire year of 2024 saw just 61 cases and 30 deaths.
The majority of the confirmed cases in 2025 have been reported in Brazil (110 cases, 44 deaths), Colombia (64 cases, 26 deaths), Peru (38 cases, 13 deaths), Ecuador (6 cases, 5 deaths), and Bolivia (3 cases, 1 death). Notably, the virus is now appearing outside of its traditional stronghold in the Amazon, with cases reported in densely populated areas such as São Paulo State in Brazil and Tolima Department in Colombia—raising fears of a potential urban outbreak.
“This year’s cases suggest a periodic reactivation of sylvatic (jungle-based) transmission cycles, with spillover infections in humans,” PAHO noted.
Health officials are also expressing concern about the proximity of several outbreaks to the Caribbean region, especially given increased travel between the mainland and Caribbean islands. While no Caribbean countries have reported cases so far in 2025, the spread of the virus to areas near the Caribbean coastline—such as northern Colombia and parts of Brazil—could heighten the risk of importation and potential local transmission, particularly in areas with low vaccination coverage and the presence of mosquito vectors.
Almost all reported infections have occurred in unvaccinated individuals, underscoring concerns about falling immunization rates. Before the COVID-19 pandemic, vaccination coverage among children aged 9–18 months in endemic countries ranged from 57% to 100%, with 10 out of 12 countries falling below the recommended 95% threshold. Coverage declined further between 2020 and 2023, leaving large swathes of the population unprotected.
Although vaccination efforts have since improved, PAHO says limited global vaccine supply remains a serious challenge, with demand outstripping availability in both the Americas and Africa.
In its assessment, PAHO called for urgent action to bolster disease surveillance, ramp up vaccination among at-risk populations, and enhance public communication to inform communities and travelers. The organization is working with national authorities to improve vaccination strategies, including the use of fractional doses and identifying high-risk groups.
Yellow fever is an acute viral hemorrhagic disease endemic to tropical areas of the Americas and Africa. In the Americas, it is transmitted mainly by sylvatic mosquitoes of the Haemagogus and Sabethes species. Symptoms typically appear three to six days after a mosquito bite and include fever, muscle pain, headache, and vomiting. While most patients recover, about 15% develop severe complications, including organ failure and death.
PAHO says it will continue to monitor the evolving situation and provide technical support to countries in managing the growing threat of yellow fever.
 has highlighted a sharp increase in yellow fever cases across the Americas.){kind=link}