International health organization sends out alert after alarming spread of disease — here's what you should know

As of February 2025, the Pan American Health Organization has issued an epidemiological alert regarding the recent increases in yellow fever rates in the Americas. While yellow fever has been rising in South America and Africa since the 1980s, reports from 2024 indicate that the disease is no longer contained within the Amazonian region. 

What's happening?

Yellow fever, caused and spread by the yellow fever mosquito, hasn't been a major public health concern since the 1800s, but its reemergence in the past five decades may be cause for concern, according to the Institut Pasteur. 

Although the disease is endemic in 13 countries across Central America, South America, and Africa, 2025 research points to outbreaks in Brazil, Colombia, and Peru — countries outside of these expected regions. 

In the past year alone, PAHO recorded 61 new yellow fever cases, 30 of them fatal. That's almost a 50% fatality rate.

But while Colombia by far is the nation most affected by the geographic expansion of the yellow fever virus, the rest of us aren't in the clear. In 2024, researchers spotted the same disease-carrying mosquito in California. 

The global redistribution of mosquitoes tends to be "facilitated by ecological factors, such as climate change and urbanization, that may enable [them] to flourish in new regions," wrote parasitology researchers Aidan Findlater and Isaac Bogoch. 

Why is the resurgence of yellow fever concerning?

According to Dr. Ajay Kohli at Acko, yellow fever symptoms start with little to no visibility and progress to headaches, fever, vomiting — and in more severe cases, jaundice, seizures, coma, kidney failure, and possible death. The 2024 and 2025 increase in yellow fever casualties means that more disease patients than ever are experiencing severe symptoms. 

Mosquito-borne diseases, including dengue and Zika virus, are becoming increasingly common. Of these, yellow fever has one of the highest fatality rates.

The WHO classifies yellow fever as a "high-impact high-threat disease, with risk of international spread, which represents a potential threat to global health security."

What's being done about yellow fever?

PAHO's key recommendations include national preparation for emergency response and universal vaccination for individuals in high-risk areas. 

Do you worry about getting diseases from bug bites? Absolutely 👍 Only when I'm camping or hiking 🏕️ Not really 🤷 Never 👎 Click your choice to see results and speak your mind.

"In 2024, most of the cases reported were in people who had not been vaccinated," the report claimed. 

According to the WHO, a single dose of the vaccine "provides life-long protection against the disease" and "effective immunity within 10 days" of its receipt. For individuals who cannot be vaccinated, such as infants or pregnant women, long-sleeved clothing and mosquito repellent may prove effective.

Still water is a breeding ground for mosquito larvae. On a communal or national level, the Institut Pasteur recommends "[eliminating] places where stagnant water can collect" in urban areas.

Join our free newsletter for weekly updates on the latest innovations improving our lives and shaping our future, and don't miss this cool list of easy ways to help yourself while helping the planet.