Visitors planning trips to Costa Rica should keep viral illnesses in perspective: hantavirus deserves awareness, but dengue and other mosquito-borne diseases remain the more common concern for travelers and residents.
Hantavirus is carried by rodents and can infect people through contact with contaminated urine, droppings or saliva, especially when particles become airborne in enclosed spaces. In the Americas, infection can lead to hantavirus cardiopulmonary syndrome, a severe respiratory illness with a fatality rate that can reach 50%.
Costa Rica has appeared in the scientific record on hantaviruses. Rio Segundo virus, linked to the harvest mouse Reithrodontomys mexicanus, was identified from Costa Rica, but it has not been associated with known human disease. The first major Central American human disease activity was later documented in Panama, where Choclo virus became the main hantavirus linked to human cases.
That distinction matters for travelers. Costa Rica has not seen a major human hantavirus outbreak like those reported in parts of South America or Panama. For most visitors staying in hotels, beach areas, urban centers or established eco-lodges, the practical risk is low. The risk rises in places where rodents may be active, especially barns, storage rooms, rustic cabins or poorly ventilated rural buildings.
The more immediate viral risk in Costa Rica is dengue. The country saw a sharp rise in 2024, with more than 27,000 confirmed cases reported by late October. Health authorities reported a major decline in 2025, with 1,802 dengue cases through epidemiological week 12, down 69.5% from the same period in 2024. Vector-control teams had eliminated 341,771 dengue breeding sites and fumigated 136,058 homes by March 23, 2025.
The latest available 2026 bulletin shows dengue still present but at lower levels than the previous surge. By epidemiological week 14, Costa Rica had reported 849 dengue cases, including 13 cases with warning signs. Chorotega had the highest number of reported cases, while the Central Pacific had the highest rate. Three people were hospitalized with dengue as of April 20.
Chikungunya has also returned to official monitoring. Costa Rica confirmed a fifth chikungunya case for 2026 on April 17, involving a woman from Tibás with recent travel to Nicaragua. Health authorities classified it as imported. The ministry had previously said Costa Rica had not registered circulation of chikungunya since 2017.
The same mosquitoes that spread dengue can also transmit chikungunya and Zika. Symptoms can overlap, including fever, body pain, headache, nausea and general malaise. Chikungunya is often marked by strong joint pain and inflammation.
The prevention steps are simple but worth taking, especially during the rainy season and in warmer lowland areas. Travelers should wear long sleeves and pants when mosquitoes are active, use appropriate insect repellent, stay in rooms with screens or air conditioning, and sleep under a bed net when rooms are exposed to the outdoors. Permethrin-treated clothing and gear can also reduce bites, but permethrin should not be used directly on skin.
For hantavirus, the advice is different: avoid rodents, do not sleep in rodent-infested spaces, and ventilate closed rural structures before spending time inside. Travelers should avoid sweeping or disturbing rodent droppings in enclosed spaces, since that can send contaminated particles into the air. WHO lists cleaning enclosed or poorly ventilated spaces, farming, forestry work and sleeping in rodent-infested dwellings among activities that can increase exposure.
Travelers should also review routine vaccinations before coming to Costa Rica. The CDC advises visitors to check vaccines and medicines at least a month before travel and to be current on routine vaccines, including measles-mumps-rubella, tetanus-diphtheria-pertussis, influenza, polio and others.
The message is preparation, not alarm. Costa Rica remains a heavily visited destination with manageable tropical disease risks for most travelers. The key is knowing where the real risks are: rodents in enclosed rural spaces for hantavirus, and mosquitoes across much broader areas for dengue, chikungunya and Zika. A few basic precautions can greatly reduce the chance that a trip is interrupted by illness.
