Costa Rica Mosquito Season
Costa Rica has peak mosquito activity during the rainy season from May through November, though the Caribbean coast receives rain year-round. The Limon province on the Caribbean coast, the Pacific lowlands, and the Osa Peninsula carry the highest risk. The Central Valley including San Jose has lower exposure due to altitude.
WHO and CDC surveillance reports indicate that the seasonal mosquito risk in Costa Rica aligns with rainfall patterns and temperature, with peak transmission of Costa Rica's most-reported disease (Dengue Fever) typically following the wet season. Travel timing should account for these climatic windows.
Where Mosquitoes Are Worst in Costa Rica
Dengue fever is the primary concern, with increasing case counts in recent years. Malaria (P. vivax) has been reduced to very low levels, mostly in the Limon province. Chikungunya and Zika have also circulated in recent years.
Aedes aegypti is the dominant urban vector. Aedes albopictus is also established. The countrys diverse microclimates mean risk varies significantly between the hot lowlands and the cooler central highlands.
Mosquito-Borne Diseases in Costa Rica
Mozzwise tracks 4 mosquito-borne diseases in Costa Rica based on WHO, CDC, and ECDC surveillance. Each entry below cross-links to a full Mozzwise disease briefing.
Dengue Fever is recorded in Costa Rica with high severity according to current surveillance. Travelers to endemic areas, young children, pregnant women, and people with prior dengue infection. A second infection with a different serotype carries a significantly higher risk of severe disease. Reported globally in: Tropical and subtropical regions worldwide — Southeast Asia, Latin America, Sub-Saharan Africa, Pacific Islands.
Chikungunya is tracked as present in Costa Rica based on historical surveillance, though active transmission is not currently flagged. Elderly travelers, newborns, and people with chronic conditions like diabetes or heart disease. The debilitating joint pain can persist for months or years, significantly affecting quality of life. Reported globally in: Africa, Asia, Indian subcontinent, Americas. Expanding into southern Europe (Italy, France, Spain).
Malaria is tracked as present in Costa Rica based on historical surveillance, though active transmission is not currently flagged. Young children under 5, pregnant women, and travelers without immunity are most vulnerable. Around 600,000 people die from malaria each year. The right precautions and prophylaxis make all the difference. Reported globally in: Sub-Saharan Africa (90% of cases), South and Southeast Asia, Central and South America, Middle East.
Zika Virus is tracked as present in Costa Rica based on historical surveillance, though active transmission is not currently flagged. Pregnant women and those planning pregnancy are the primary concern. The virus can cause devastating birth defects including microcephaly. Most adults recover without issues within a week. Reported globally in: Tropical Americas, Southeast Asia, Pacific Islands. Ongoing low-level transmission since the 2015-2016 epidemic.
How to Avoid Mosquito Bites in Costa Rica
Public health agencies converge on a layered approach to reducing mosquito bites in Costa Rica. The core recommendations across CDC, WHO, and ECDC are as follows.
Skin-applied repellents. CDC recommends EPA-registered repellents containing one of four tested active ingredients: DEET, picaridin, IR3535, or oil of lemon eucalyptus / para-menthane-diol. CDC advises applying sunscreen first and repellent on top, and reapplying at the interval stated on the product label.
Permethrin-treated clothing. WHO and CDC both recommend permethrin treatment of trousers, long-sleeved shirts, and socks for settings with sustained mosquito exposure. Permethrin binds to fabric and is effective against both Aedes and Anopheles species. It is not applied to skin.
Accommodation. Air-conditioned rooms with intact window screens substantially reduce indoor exposure. Bed nets — ideally permethrin-treated — are standard in open-air or budget accommodation. WHO emphasises removing standing water around accommodation, as even bottle caps, plant saucers, and water-storage containers can support Aedes breeding.
Timing. Aedes vectors active in cities and resort areas typically bite in daylight, with peaks in early morning and late afternoon. Anopheles vectors active in forested or rural areas typically bite at night.
For travelers to malaria transmission zones in Costa Rica, CDC and WHO recommend prescription chemoprophylaxis. The specific regimen depends on geography and individual circumstances and is a personal decision with a qualified travel health professional.
For product reviews and brand comparisons see our [travel prevention guides](/guides). Personal decisions on repellent choice, vaccination, or any prescription medication remain with a qualified travel health professional.