Costa Rica reported its first officially confirmed case of yellow fever in nearly 70 years, a uncommon medical occurrence in the nation’s contemporary history.
The Ministry of Health announced the news on Sunday after lab tests confirmed the infection, breaking the country’s extensive streak of not having the mosquito-borne illness since the 1950s.
The patient is a 29-year-old American female who has recently returned from Costa Rica from Peru’s Amazonian region, a region in which yellow fever transmission occurs. Per officials, she started feeling symptoms like fever and muscle ache on October 7, before she arrived in Costa Rica the next day.
The medical professionals from the National Institute for Research in Nutrition and Health (INCIENSA) tested and confirmed the diagnosis, leading to her hospitalization immediately in a public hospital operated by Costa Rica’s Social Security Fund (CCSS). The Ministry explained that she is undergoing specialized care and is being kept under close monitoring as her condition stabilizes.
The authorities termed the case as an imported case, emphasizing that the woman had not been vaccinated for yellow fever, a requirement for travel to high-risk areas of South America and Africa. The vaccine, which gives a lifetime immunity following a single dose, is advised at least 10 days prior to travel to endemic areas.
Yellow fever is a viral disease spread by the bite of infected mosquitoes, primarily Aedes aegypti and Haemagogus. The disease commonly begins with fever, chills, headache, and muscle pain. Most patients recover after a brief period, but others develop a severe “toxic” phase that may lead to jaundice, hemorrhage, and liver or kidney failure. The World Health Organization estimates that the severe form has a mortality rate of up to 50%.
Following the confirmed case, Costa Rican authorities quickly implemented national surveillance and containment measures. Vector control squads were sent in to destroy areas of mosquito breeding grounds, particularly where the woman had visited. The Health Ministry also highlighted the need for immunization and safe travel measures, urging visitors to produce evidence of vaccination if arriving from endemic areas.
This case is one of many during a regional outbreak of yellow fever infections. Statistics from the Pan American Health Organization (PAHO) indicate over 200 confirmed cases for the Americas in 2025, with particularly increased cases in Colombia, Brazil, and Peru. The death rate for the region is around 40%, leading several countries to intensify preventive campaigns.
Costa Rica, in spite of its rainy and mosquito-populated environment and tropical climate, has been yellow fever-free since 1956. A minor rural epidemic was the last time the virus struck in the country, and that was in 1956. Aggressive public health measures, such as broad vaccination, rigorous disease surveillance, and effective mosquito control, have prevented the virus from making another reappearance for almost seven decades.
Health Minister Mary Munive reassured the public that everything is under control. “We have the tools to manage this,” she said. “Our medical staff are trained, our systems are in place, and we are coordinating closely with global health authorities to avoid local transmission.”
Government officials are also collaborating with tour firms and border control to make sure all travelers coming from risk zones meet vaccination criteria. Costa Rica has since May 2025 toughened entry restrictions, requiring evidence of vaccination or residence in a low-risk country prior to entry.
Health professionals advise visitors to seek advice from the Centers for Disease Control and Prevention (CDC) or local health authorities prior to visiting tropical countries. In Costa Rica, all individuals who fall ill after visiting high-risk nations should immediately seek medical care and report their travel to physicians.
While Costa Rica probes this lone case, the government’s concern continues to be containment, education, and prevention. Since tourism is back to pre-pandemic levels, public health alertness is crucial to making sure residents and visitors alike are safe in one of the world’s most sought-after destinations.
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