New clinical guidelines aim to improve care for severe yellow fever patients in the Americas

Washington, D.C., March 27, 2026 (PAHO) - The Pan American Health Organization (PAHO) has released new clinical guidelines for the management of patients with severe yellow fever. The guidelines aim to strengthen the capacity of health workers and support timely, life-saving care.

Yellow fever is a mosquito-borne viral disease that can cause outbreaks with a high number of cases and deaths in a short period of time. As there is no specific treatment, early detection of suspected cases, identification and close monitoring of patients at higher risk of severe disease, and timely referral to intensive care units are critical to reducing complications and saving lives.

"This guideline provides evidence-based clinical recommendations to support decision-making and improve the care of severe yellow fever cases," said Ángel Rodríguez, PAHO advisor on clinical management of emerging diseases. "It also serves as a key tool to strengthen preparedness and response across health services in the Americas."

The new guidance complements PAHO's 2023 clinical management guidelines and is part of the Organization's regional response to the public health emergency recorded between 2024 and 2025, when the average case fatality rate for yellow fever reached 45%. It brings together updated clinical and epidemiological information, along with practical recommendations on case detection, diagnosis, initial management, severity classification, and comprehensive patient care.

Yellow fever is caused by a virus of the Flavivirus genus and is transmitted through mosquito bites. In the Region, the sylvatic (jungle) cycle primarily involves mosquitoes of the Haemagogus and Sabethes genera, while urban transmission can occur through Aedes aegypti and Aedes albopictus. Severe cases can rapidly progress to serious complications such as acute liver failure, requiring specialized intensive care.

In recent years, the disease has re-emerged as a growing public health concern in the Americas. Since 2024, outbreaks have been reported in several South American countries, including in areas outside the traditional Amazon basin, confirming an expansion of risk zones.

In 2025, a total of 346 confirmed cases and 143 deaths were reported across seven countries in the Region: Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela. In the first seven weeks of 2026, 34 human cases and 15 deaths have already been confirmed in Bolivia, Colombia, Peru, and Venezuela.

While there is no specific treatment for yellow fever, vaccination remains the most effective preventive measure. A single dose provides lifelong immunity. Most confirmed cases and deaths reported in 2025 and 2026 occurred among unvaccinated individuals.

PAHO continues to support countries in strengthening epidemiological surveillance, expanding vaccination coverage among at-risk populations, and improving the capacity of health services for early detection and timely clinical management of severe cases.

The new guidelines aim to contribute to these efforts by providing health teams with a practical, evidence-based tool to deliver safe, standardized care and reduce mortality associated with the disease.