The Pan American Health Organization (PAHO) has issued an urgent epidemiological alert following a significant rise in yellow fever cases across the Americas in the early months of 2025.
As of March 22, the number of confirmed human cases has more than doubled compared to all of 2024, raising concerns about the potential spread of the disease.
In the first three months of 2025, there have been 131 confirmed cases of yellow fever, resulting in 53 deaths. This is in stark contrast to 2024, when 61 cases were reported, 30 of which were fatal. The cases have been reported across Bolivia, Brazil, Colombia, and Peru, with the disease spreading beyond the traditionally affected Amazon region.
Geographic spread and emerging concerns
The majority of cases have been recorded in Brazil, where 81 cases and 31 deaths have occurred. In Colombia, 31 cases and 13 deaths have been reported, while Peru has recorded 18 cases and 8 deaths. A particularly troubling development is the emergence of new cases in Tolima, Colombia, starting in October 2024, which signals the virus spreading to areas not previously affected. These regions, particularly those involved in agriculture, present a heightened risk of exposure to the virus.
The situation in Brazil’s São Paulo state is also cause for concern, with 34 cases and 19 deaths reported. The state’s proximity to densely populated urban centers increases the risk of a larger outbreak, making containment efforts critical.
The need for immediate action
Yellow fever is a serious viral disease transmitted by mosquitoes. While it can be fatal, the disease is preventable through vaccination. PAHO reports that most of the individuals affected so far were not vaccinated, underscoring the importance of immunization in preventing further spread.
In response to the surge in cases, PAHO has called for intensified vaccination efforts in at-risk areas, targeting coverage rates above 95%. In an alert issued on March 27, PAHO emphasized the need for countries to review their vaccine stocks, strengthen rapid response plans for potential outbreaks, and ensure that travelers to endemic areas are adequately informed and vaccinated.
The resurgence of yellow fever in the Americas brings to mind the epidemic that hit Brazil between 2016 and 2018, highlighting the continued public health threat posed by the disease. The yellow fever virus persists in a sylvatic cycle between mosquitoes and non-human primates across 13 countries and territories in the region. Since 1960, yellow fever has caused 9,591 human cases and 3,444 deaths in the Americas.
In light of the recent spike in cases, PAHO’s February risk assessment identified a high risk of yellow fever outbreaks across the region. The organization has committed to closely monitoring the situation and assisting affected countries in implementing the best strategies for preventing and controlling the disease.
As the outbreak unfolds, public health experts are stressing the need for a coordinated response to contain the disease and prevent further loss of life.
