CDC Issues Travel and Vaccine Notice for Yellow Fever in South America

An ‘increased number of cases of yellow fever have been reported in parts of South America,’ the health agency says.

The Centers for Disease Control and Prevention headquarters in Atlanta on April 23, 2020. Tami Chappell/AFP via Getty Images

The U.S. Centers for Disease Control and Prevention issued a travel notice on Tuesday for the entire South American continent due to elevated levels of yellow fever in several countries.

“An increased number of cases of yellow fever have been reported in parts of South America,” the CDC said in its bulletin, referring to a report from the Pan American Health Organization, an arm of the World Health Organization (WHO), that showed that cases of the viral disease have increased during the first three months of 2025.

Yellow fever is a viral illness transmitted by mosquitoes. It is primarily found in tropical areas and spawned numerous epidemics worldwide in the 18th and 19th centuries.

The Pan American Health Organization reported on March 31 that 131 yellow fever cases had been confirmed, leading to 53 deaths in the Americas for the first three months of 2025. It noted that 61 cases and 30 deaths were reported across 2024. The cases and deaths reported this year have been relegated primarily to Brazil, Colombia, and Peru, but the organization said that cases have been found “beyond the traditionally affected Amazon region.”

In the Tuesday notice, the CDC reported that more cases of yellow fever have been reported in new areas inside Peru, Bolivia, and Colombia, and that “travelers to these newly affected areas are now recommended to get vaccinated” for the virus. People who are traveling to those countries are advised to receive a vaccine at least 10 days before travel.

“Travelers should seek medical care if they develop fever, chills, headache, backache, or muscle aches during or after travel in an affected area,” the agency advised. “Travelers should let their healthcare professional know that they’ve been to an area where yellow fever cases are reported.”

The CDC bulletin comes as Colombia’s government declared a nationwide health emergency late on Wednesday due to an increase in yellow fever cases.

The outbreak has resulted in 74 confirmed cases and 34 deaths since the start of last year, said Health Minister Guillermo Alfonso Jaramillo. Jaramillo said the most critical situation is in Tolima, in central-west Colombia, where 22 cases have been detected.

Yellow fever is caused by a virus transmitted by the bite of infected mosquitoes in the Aedes genus, although the majority of infections are asymptomatic. According to the World Health Organization, people who develop symptoms can show signs of fever, muscle pain, headache, loss of appetite, and nausea or vomiting.

“The incubation period for yellow fever is 3 to 6 days. Many people do not experience symptoms. Common symptoms include fever, muscle pain, headache, loss of appetite, nausea, or vomiting. In most cases, symptoms disappear after 3 to 4 days,” the U.N. health body says.

But a small percentage of cases can enter a “more toxic phase” within 24 hours of having recovered from those initial symptoms. The secondary phase can include a return of a high fever, and multiple organ systems can be impacted, generally the kidneys and liver, WHO says.

About half the people who enter the toxic phase die within seven to 10 days, it says.

During the second phase, officials say, patients can develop jaundice, or the yellowing of the skin and eyes, as well as abdominal pain and dark urine. Bleeding can also occur from the stomach, nose, eyes, and mouth.

Reuters contributed to this report.