Sao Paulo's Yellow Fever Risks Continue in 2025

The reemergence of yellow fever in the Brazilian state of São Paulo over the past 23 years has highlighted the need to be fully immunized before visiting endemic areas in 2025.

The São Paulo State Health Department recently confirmed the first human yellow fever case in January 2025.

According to a study published by Rev Bras Epidemiol in December 2024, five yellow fever outbreaks from 2000 to 2023 led to 679 human cases. Epizootic surveillance actions in non-human primates intensified in 2017 when the virus circulated in areas without vaccine recommendations in the state.

A previous study found the metropolitan region of São Paulo city YF outbreak during 2017–2018 revealed that 36 deaths were due to three genetic variants of sylvatic YFV that belong to the South American I genotype and that were related to viruses previously isolated from other locations in Brazil (Minas Gerais, Espírito Santo, Bahia, and Rio de Janeiro states).

According to these researchers, each variant represented an independent YF virus introduction into Sao Paulo.

"The recently confirmed case of yellow fever infection in São Paulo reinforces the importance of vaccination before traveling to many parts of Brazil, including popular urban destinations," commented Jeri Beales, MSN, RN.

"The 2017 yellow fever outbreak in Brazil marked an important change in CDC yellow fever recommendation for Brazil-bound travelers, including major cities like São Paulo, Rio de Janeiro, Curibita, and Salvador."

"Ideally, the yellow fever vaccine is given at least 10 days before arrival to a risk area, and only clinics certified with CDC can provide the vaccine," added Beales, who leads Destination Health Clinic, a Boston-area travel health provider specializing in health education and vaccination for international travelers.

As of January 21, 2025, the U.S. CDC and the U.K. Health Security Agency recommends international travelers visit a travel clinic or pharmacy to discuss travel vaccine options about one month before visiting Brazil in 2025. This year, about 8 million people may visit Sao Paulo.

According to the CDC, the yellow fever vaccine is recommended for many destinations in Brazil, including Sao Paulo, but may not required for entry.  

Note: This Vax-Before-Travel news article was updated with related insight on Jan. 22, 2025.