Dengue, chikungunya and malaria figures with their dates, where malaria occurs in Costa Rica, why yellow fever vaccination is not recommended but a certificate can be required, and how to judge day-biting and night-biting mosquitoes.
Dengue in Costa Rica: the newest dated figures
Dengue is the mosquito-borne infection most likely to affect a winter visitor to Costa Rica. The Pan American Health Organization reported 5,426 cumulative suspected dengue cases in Costa Rica through epidemiological week 39 of 2026, with 307 cases in that week alone. Across the Americas, the same report counts 1,813,577 suspected cases, 565,945 laboratory-confirmed cases and 614 deaths, a case fatality rate of 0.034%. PAHO calls the regional figure 55% below the same period in 2025. An earlier PAHO update of 20 October 2026 gave 5,302 suspected Costa Rican cases between weeks 1 and 37, of which 2,393 were confirmed, with no deaths and an incidence of 102.47 per 100,000 people. Three serotypes circulated, and DENV-3 was predominant.
Chikungunya: small numbers, rising late-summer reporting
Chikungunya is present in Costa Rica, but at far lower numbers than dengue. The Pan American Health Organization recorded 690 suspected chikungunya cases in Costa Rica between weeks 1 and 38 of 2026, of which 539 were laboratory-confirmed. In 2025, Costa Rica had reported eight suspected cases by week 53, with none confirmed. The European Centre for Disease Prevention and Control, in a situation update published on 5 October 2026 with data as of 30 August 2026, reports 300 Costa Rican cases in 2026 and notes a significant increase in reporting during the second half of August. Globally, that update counts 250,051 cases and 87 deaths in 2026. For comparison, Brazil recorded 127,676 cases by the end of week 34.
Malaria: limited areas and a disagreement between authorities
Malaria risk in Costa Rica is low and geographically limited, but official guidance does not fully agree on where it occurs. The United Kingdom's TravelHealthPro puts malaria at low risk in Limon Province, excluding the city of Limon, also called Puerto Limon, and at very low risk in the rest of the country, including that city. The United States Centers for Disease Control and Prevention records malaria as present in the provinces of Alajuela and Limon, and says transmission is rare to absent elsewhere. The two authorities therefore name different malaria areas. The World Health Organization's World malaria report 2025, published on 4 December 2025, estimates 240 malaria cases and no deaths in Costa Rica in 2024, including 240 indigenous cases. Costa Rica sits in the E-2025 group of countries aiming to halt local transmission.
Yellow fever: no vaccination recommended, a certificate can still be required
Costa Rica carries no risk of yellow fever, so vaccination is not recommended for travel there. A certificate can nevertheless be required at the border. TravelHealthPro states that proof of vaccination is required for travellers aged nine months or over arriving from countries with risk of yellow fever transmission, and its country page adds Rwanda, Tanzania and Zambia to that list. The Centers for Disease Control and Prevention also records that yellow fever vaccination is not recommended, and that it is required for travellers aged nine months and older arriving from countries with risk for yellow fever virus transmission. The practical point for a European traveller is that the certificate rules depend on the route taken, not on Costa Rica itself. Check your itinerary against both sources before booking.
Which mosquitoes bite by day and which by night
Bite timing matters because it decides when protection is needed. TravelHealthPro's factsheet 38, updated on 13 August 2026, states that some mosquitoes bite during daylight hours, including Aedes species, while others are more active from dusk to dawn, including Anopheles species. It adds that Aedes aegypti can bite at night in well-lit areas, and that Anopheles may be active by day, at dawn and dusk, and through the night depending on species and place. The World Health Organization's chikungunya fact sheet, updated on 14 April 2025, says the mosquitoes that spread chikungunya bite primarily during daylight hours, and that Aedes aegypti feeds both indoors and outdoors. Daytime cover therefore protects against dengue and chikungunya, and evening cover against malaria.
Repellent and clothing: what the guidance actually specifies
Repellent guidance is specific and worth following closely. TravelHealthPro recommends repellent containing DEET at 50% concentration for all travellers over two months, provided it can be tolerated, and says protection does not increase further beyond 50%. Icaridin has similar properties at 20%. DEET should be applied after sunscreen, and a sunscreen of 30 to 50 SPF should be used. The World Health Organization recommends repellents containing DEET, IR3535 or icaridin, applied according to the product label, and does not set a concentration in its chikungunya fact sheet. Both sources advise clothing that minimises skin exposure, and the World Health Organization also advises window and door screens to stop mosquitoes entering homes. Read the label on any product you carry.
When a bed net matters, and how to use one
A bed net matters most where malaria occurs and where sleeping accommodation lets mosquitoes in. TravelHealthPro states that all travellers to malaria-endemic areas should sleep under a mosquito net unless the room is well screened or has working, switched-on air conditioning where mosquitoes cannot enter. Doors and windows to sleeping accommodation should be screened with fine mesh. The World Health Organization advises insecticide-treated nets for people who sleep during the daytime, giving young children, sick patients and older people as examples. For babies under two months, TravelHealthPro says to use clothing and insecticide-treated nets draped over cots and prams, secured around the edges, and notes that DEET is not recommended under two months. On a short winter trip, a net is reasonable insurance.
Sources
- Report on the epidemiological situation of dengue in endemic countries of the Americas, as of epidemiological week 39, 2026: Pan American Health Organization / World Health Organization
- Epidemiological Update: Dengue and Chikungunya in the Americas Region, 20 October 2026: Pan American Health Organization / World Health Organization
- Costa Rica country information: TravelHealthPro (UK National Travel Health Network and Centre)
- Costa Rica, CDC Travelers' Health: US Centers for Disease Control and Prevention
- Insect and tick bite avoidance: TravelHealthPro (UK National Travel Health Network and Centre)
- Chikungunya (fact sheet): World Health Organization
- Chikungunya virus disease worldwide overview, situation update September 2026: European Centre for Disease Prevention and Control
- World malaria report 2025: World Health Organization
This article is general information, not medical advice. Ask a doctor or pharmacist about your own health.