Yellow Fever Outbreaks

Yellow Fever Outbreaks July 2025

Scientists believe yellow fever has existed for about 3,000 years, originating in Africa and spreading to the Americas in the 17th century. In the 18th and 19th centuries, yellow fever (YF) was considered one of the most dangerous mosquito-transmitted infectious diseases. According to the World Health Organization (WHO), as of July 2025, the YF virus has become endemic in tropical areas of Africa and 13 countries in the Americas. As of June 29, 2025, the overall risk associated with the yellow fever virus in the Americas Region, particularly in endemic countries such as Brazil, is classified as ¨High.¨

Africa Yellow Fever Outbreak

Since the beginning of 2023, documented probable and confirmed cases of yellow fever have been reported in Burkina Faso, Cameroon, the Central African Republic, Chad, the Republic of the Congo, Côte d'Ivoire, the Democratic Republic of the Congo, Guinea, Niger, Nigeria, South Sudan, Togo and Uganda. In July 2025, the Angolan Ministry of Health reported seven confirmed cases of yellow fever from 5 provinces: Luanda, Benguela, Malanje, Huíla, and Huambo. On March 28, 2024, the U.S. Centers for Disease Control and Prevention (CDC) issued a Level 2 Travel Health Notice regarding a yellow fever outbreak in Nigeria. Between January 2024 and November 2024, 29 confirmed YF cases were reported in Nigeria. The overall risk at the regional level was reassessed as moderate.

The Americas' Yellow Fever Outbreaks

Yellow fever human cases and deaths by country and sub-national geographic distribution from 2000 to 2022 are posted by the PAHO. As of June 2025, countries in the Americas Region had reported about 200 confirmed human cases of yellow fever, including 85 deaths (CFR 40%). Yellow fever cases were reported in the Plurinational States of Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, and the Bolivarian Republic of Venezuela. In 2024, 61 human cases of yellow fever were confirmed in the Americas Region, including 30 deaths (CFR= 50%), among five countries: Bolivia, Brazil, Colombia, Guyana, and Peru. In February 2025, the PAHO published a Public Health Risk Assessment related to yellow fever, confirming the high risk of YF outbreaks in the Americas. On April 15, 2025, the U.S. CDC issued a Level 2 - Practice Enhanced Precautions, Travel Helath Advisory regarding YF outbreaks in the Americas. In 2024, the PAHO reported 61 YF cases, 30 of which were fatal.

In Brazil, yellow fever transmission historically occurs within a sylvatic cycle in the Amazonian Region. Between 2020 and 2025, three cases of yellow fever were confirmed in the Peixe and São Salvador regions. São Paulo State Health Department confirmed that 679 human cases were recorded from 2000 to 2023. Brazil experienced its largest recorded outbreak of yellow fever in 2018. Yellow Fever cases have been confirmed in Pará State, Amazon Region of Brazil, for three decades. In March 2025, five confirmed deaths and 27 cases of YF were reported on Marajó Island. As of 2025, Australia, the U.S. CDC, Hong Kong, and the United Kingdom have issued travel alerts regarding Brazil's YF outbreaks.

Bolivia reported three YF cases, including one death (CFR 33%), in the city of Palos Blancos in the La Paz Department in 2025. Eight YF cases occurred in 2024 and five in 2023.

Since October 2024, the YF virus has appeared in areas not previously affected in past years in the Colombian department of Tolima. As of June 9, 2025, there have been 104 cases, with 45 deaths, primarily in Tolima. Although the vaccine for yellow fever was incorporated into Colombia's national immunisation schedule for children in 2002 in endemic regions, coverage remains low among adults.

The Ecuadorian Ministry of Public Health reported 10 confirmed fatal yellow fever cases and eight related fatalities as of June 21, 2025, from the provinces of Morona Santiago and Zamora Chinchipe.

Peruvian authorities issued an epidemiological alert due to a sharp rise in yellow fever cases in areas of the Peruvian Amazon in 2025, including Huánuco, San Martín, and Amazona districts. As of April 24, 2025, Peru has reported 32 confirmed cases of yellow fever, resulting in 10 deaths. In comparison, Peru reported 19 confirmed cases of yellow fever, with nine deaths, for 2024.

United States Yellow Fever Outbreaks

In the United States, the Butte County Mosquito and Vector Control District in California detected the Aedes aegypti (yellow fever) mosquito in 2023. Aedes aegypti mosquitoes were found for the fourth consecutive year in Butte County. The American Society for Microbiology provides a history of the emergence of yellow fever outbreaks in the United States.