Given represents a 40%lethality rate, considered high, but varies according to the locality; In the state of São Paulo, the largest number of deaths from the disease was recorded in seven years
Cases of yellow fever in the Americas region tripled by 2025 compared to the same period in 2024, according to the World Health Organization (). Until May 2, 212 cases were confirmed in five countries, against 61 last year – an increase of 247%. Brazil concentrates most infections, with 110 cases and 44 deaths. There were also records this year in Bolivia, Colombia, Ecuador and Peru. In all, 85 deaths have already been reported to WHO. The data represents a 40%lethality rate, considered high, but varies according to the locality. In Ecuador, for example, the four reported cases resulted in deaths (100% lethality).
Different regions
In 2024, human cases of yellow fever were notified mainly in the Amazon region of Bolivia, Brazil, Colombia, Guyana and Peru. This year, however, cases were detected mainly in other areas, including the interior of São Paulo. In the state of São Paulo, the largest number of deaths from the disease was recorded in seven years: there were 55 cases and 31 deaths. There was also notification in the states of Minas Gerais, with 10 cases and 5 deaths; Pará, with 44 cases and 7 deaths; and Tocantins, with 1 fatal case. Most infected were male, representing 89.6% of patients, and ages ranged from 10 to 75 years. Only one person had a yellow fever vaccination record.
All patients reported exposure to wild or forest areas, either through occupational or recreational activities. Still, it is not possible to ignore that the disease can have an urban cycle. For WHO, the risk to public health in affected countries is considered high, especially given the fall in vaccinations since the Covid-19 pandemic. “The increase in confirmed cases of yellow fever in the Americas highlighted the need to strengthen surveillance, vaccination of at -risk populations and risk communication strategies for people who travel to areas where vaccination is recommended,” the organization evaluates.
The disease
Yellow fever is caused by an arbovirus transmitted to humans mainly by Haemagogus mosquito bite and aedes aegypti. Transmission occurs by two different types of cycles, wild and urban. In the wild cycle, monkeys are the main hosts and vectors are mosquitoes of Haemagogus and Sabethes genres. Here, humans participate as accidental hosts when they frequent areas of forest. In the urban cycle, humans are the only hosts with epidemiological importance and transmission occurs through Aedes aegypti mosquitoes infected with the virus.
What are the symptoms?
According to Moacyr Silva, infectologist at Hospital Israelita Albert Einstein, yellow fever has symptoms similar to those of various infectious diseases, not having a characteristic sign. “Symptoms include body pain, fever and malaise. In later and serious cases, spontaneous bleeding may occur,” he said in an interview with Estadão. “If the person has a fever and continuous malaise, it is important to look for a basic health unit to evaluate the clinical picture.”
Importance of vaccination
Vaccination is the most effective form of combating disease. Currently, the vaccination calendar foresees a dose of the immunizer at 9 months of age and another at 4 years. In people over 5 years old previously vaccinated, the single dose scheme is used. The immunizer is offered free of charge at health posts across the country.
*With information from Estadão Content
Posted by Fernando Dias
