Costa Rica's northwest has a chikungunya notice. Here's how to plan around it.
Guanacaste and Alajuela are under the only active CDC chikungunya notice among this winter's destinations, and dengue is running above last year. The Pacific dry season helps, a daytime repellent habit covers most of the loop, and Arenal and the Caribbean coast add a travel-clinic question.
Costa Rica has the only active CDC chikungunya notice among this winter's destinations. It covers the northwest, where a local outbreak began in July at Playa Langosta, next to Tamarindo, and dengue is running above 2025 as well. Both spread through a mosquito that bites in daylight, so repellent goes on in the morning over sunscreen and again in the late afternoon. If your route includes Arenal or the Caribbean coast, see a travel clinic 4–6 weeks before you fly and ask about the CDC's malaria advice for those provinces.
The classic first trip to Costa Rica loops through the Guanacaste beaches around Tamarindo, the Arenal volcano at La Fortuna, the Monteverde cloud forest and Manuel Antonio. From December to April most of it sits in the Pacific dry season, the quietest months for mosquitoes on that side of the country. This winter adds a CDC Level 2 travel notice for chikungunya in the northwest, and dengue has run ahead of last year since May. Daytime repellent handles most of both, and a few stops carry extra questions worth settling before you book.
The chikungunya notice, in plain terms
Chikungunya is a viral illness spread by Aedes mosquitoes, the same day-biting species that carries dengue. Costa Rica saw imported and scattered cases in April 2026, some linked to travel in Nicaragua. On July 1 the health ministry identified a local outbreak at Playa Langosta in Santa Cruz, Guanacaste, next to Tamarindo. By mid-July the ministry had confirmed 48 cases by lab test, and in August the social security system reported more than 400 emergency and outpatient visits for the illness. By the end of August, European surveillance counted 300 chikungunya cases in Costa Rica for 2026, with a sharp rise in the second half of the month and local transmission in Alajuela and Guanacaste.
The CDC's Level 2 notice, last updated July 30, 2026, lists Guanacaste, Alajuela and Heredia provinces plus parts of Puntarenas and San José. If you're staying in Puntarenas (Monteverde, Manuel Antonio) or around San José, check the CDC map to see whether your area is covered. CDC recommends chikungunya vaccination for travelers visiting an outbreak area and advises pregnant travelers to reconsider travel to the affected areas, especially close to delivery. Raise both at a travel clinic. The notice could be updated or lifted by the time you travel, so check it again the week before you fly.
Dengue is running above 2025
Costa Rica is also on the CDC's global dengue list, a Level 1 notice for countries with higher-than-usual case counts or more cases than expected among returning US travelers. Through mid-May, cases ran 22% below 2025, with Guanacaste's Chorotega health region reporting the most. Then they rose sharply. By mid-August the health ministry counted 3,437 cases, about 1,000 more than at the same point in 2025, and the count kept climbing into September. By August the Central Norte region had the most cases, and Pacífico Central, which includes Quepos, Manuel Antonio and Jacó, had the highest rate for its population.
The Aedes mosquito behind dengue and chikungunya breeds in small pools of standing water and bites in daylight, with peaks after sunrise and before sunset. Our dengue & Zika daily routine has the full schedule. On a Costa Rica trip it comes down to three habits.
Before the beach, the zip line or the drive. Sunscreen goes on first; repellent sits on top.
Water, sweat and rain shorten any label's protection window. Our repellent timing guide has the numbers.
The second Aedes peak overlaps beach no-see-um hour. Repellent on ankles and calves covers both.
The classic loop, split by risk
The main stops fall on two sides of a line.
Guanacaste · Monteverde · Manuel Antonio
The quietest months for mosquitoes here. Guanacaste is inside the chikungunya notice, and Pacífico Central had the top dengue rate in August.
- Outside the CDC's malaria provinces: bite precautions only
- Daytime repellent for dengue and chikungunya
- Feet-to-knees repellent for beach no-see-ums at dawn and dusk
- Monteverde is cool and light on bites
Arenal · La Fortuna · Puerto Viejo · Cahuita · Tortuguero
The two provinces where the CDC says malaria transmission occurs. Alajuela, home to Arenal, is also inside the chikungunya notice.
- Travel clinic 4–6 weeks out with your exact route
- Permethrin-treated clothes for rainforest hikes and night tours
- Repellent at dusk as well as by day
- The Caribbean side is buggy year-round
Arenal, the Caribbean and the malaria question
The CDC's traveler page for Costa Rica says malaria transmission occurs in Alajuela and Limón provinces, with rare to no transmission elsewhere. For those two provinces it lists several prevention medicines. For the rest of the country it recommends no medicine, only bite precautions, which leaves Guanacaste, Monteverde, Manuel Antonio and San José outside the list. Costa Rica started 2026 with imported malaria cases.
What we suggest you do with this: if your route includes La Fortuna, the Arenal area, Puerto Viejo, Cahuita or Tortuguero, book a travel-medicine appointment 4–6 weeks before departure. La Fortuna is in Alajuela; the Caribbean coast is in Limón. Bring the exact plan, including how many nights you'll spend in each place, and ask whether the CDC's recommendation applies to where you'll actually be. Our malaria-zone checklist covers the rest of the preparation.
Whatever the clinic decides, malaria mosquitoes bite from dusk to dawn. Repellent at sunset, long sleeves on night tours and a screened or air-conditioned room cover most of that exposure.
The buggiest stops: the Caribbean coast and Tortuguero
Limón province is where Costa Rica's bites stop being seasonal. The Caribbean side stays humid through the winter and has a reputation for being buggy year-round. Puerto Viejo and Cahuita are known for beach sand flies at dawn and dusk. Tortuguero's trails and canals have a reputation for heavy rainforest mosquitoes, especially around riverside lodges.
Rainforest stays here and elsewhere in the country bring a second insect into play. The CDC Yellow Book names Costa Rica among the most common sources of cutaneous leishmaniasis in travelers, a skin infection spread by tiny forest sand flies. They bite from dusk to dawn and are small enough to pass through ordinary mosquito netting. CDC's advice is permethrin-treated clothing and gear, which also helps against mosquitoes. Permethrin goes on fabric at home, never on skin. See a doctor about any bite sore that won't heal after the trip.
Beach no-see-ums in Guanacaste
On Guanacaste's beaches, Tamarindo included, the most common complaint is biting midges, often called no-see-ums, sand flies or sand fleas. They leave itchy, delayed welts on ankles and calves. They are weak fliers, so a steady breeze keeps them down, and still air at dawn and dusk brings them out.
Timing does most of the work. Spend beach time in the breezy middle of the day, put repellent on feet, ankles and calves before a sunset walk, wear light trousers for beach-level dinners, and shower afterward. Our Barbados sand fly guide explains the insect in more detail.
Where you're staying
Here is how the main stops compare for a December–April trip.
Guanacaste: Tamarindo, Liberia & Papagayo
Inside the CDC chikungunya notice, with July's local outbreak at Playa Langosta next to Tamarindo. Dry-season mosquitoes are few, and dawn and dusk midges on the beach are the usual complaint.
Arenal & La Fortuna
In Alajuela province, so it is inside the chikungunya notice and in one of the two provinces where CDC lists malaria prevention medicines. Mosquitoes are usually modest; large biting flies around dusk draw more complaints.
Monteverde
Cool and breezy at about 1,400 m, and mosquitoes are rarely a problem. Outside the malaria provinces; check the CDC map to see whether the chikungunya notice reaches it.
Manuel Antonio & Quepos
Pacífico Central had the country's highest dengue rate by August, so the daytime routine matters most here. Lowland humidity means more bites than in the mountains.
Caribbean coast & Tortuguero
Limón province, one of CDC's two malaria-prevention provinces, with dengue present and wet weather through the winter. Beach sand flies at dawn and dusk and heavy rainforest mosquitoes at Tortuguero make it the buggiest stop on most itineraries.
San José & the Central Valley
At about 1,150 m, dengue mosquitoes are fewer than on the coasts, and there is no malaria. Parts of San José province are inside the chikungunya notice, so keep the daytime habit.
The dry season helps, with limits
December to April is the dry season in Guanacaste and along the central Pacific coast, and residents report very few mosquitoes on the Pacific side from January to early April. Dengue and chikungunya usually build in the rainy months, roughly May to November.
There are limits. The 2026 outbreaks are recent and may not have ended by December, and in October the Pan American Health Organization warned of a strengthening El Niño and of outbreaks outside the usual seasons. Arenal and the Caribbean coast also stay humid all winter, and bites continue there.
What travelers report
Paraphrased from forum threads and reviews and linked so you can read them in full. None is dated to this season, and individual trips vary with weather, wind and where you stay.
- Hotel Pasatiempo (Tamarindo) · July · 2023
A July 2023 reviewer said the whole property had a mosquito problem, worst in the room and on the patio. The pool area also had lots of mosquitoes, which made it hard to enjoy with young children. TripAdvisor ↗
- Tamarindo
One visitor said no-see-ums bit her husband heavily while she was rarely bitten. Another poster had no bug trouble at all and put it down to the wind. TripAdvisor ↗
- Guanacaste beaches
A visitor got dozens of itchy bites on the calves and ankles from beach biters. The bites showed up a couple of days after the beach visit. TripAdvisor ↗
- Puerto Viejo de Talamanca / Cahuita · dawn and dusk
Posters said sand fly bites land mostly on the legs, feet and ankles on the beach at dusk or early morning. Often one person in a group reacts while the others are untouched. They advised DEET or picaridin, showering after the beach and skipping the beach at dusk. TripAdvisor ↗
- Tortuguero
Experiences varied widely. One traveler in long sleeves and heavy DEET reported more than 100 bites at a riverside lodge, worst on the jungle trails behind it, while others got only a handful in a month. A lodge owner said September and October have the fewest mosquitoes. TripAdvisor ↗
- Arenal / La Fortuna
Several visitors had few or no mosquito bites in La Fortuna town and on night hikes. One said the worst bites came from large horsefly-like flies around dusk. TripAdvisor ↗
- Monteverde
A long-time resident and several visitors said mosquitoes are scarce in Monteverde compared with lowland Jacó. One group still reported heavy biting on a cloud forest tour. TripAdvisor ↗
- Manuel Antonio
A traveler got only a handful of mosquito bites on a six-day Manuel Antonio trip and then came down with dengue. Forum members stressed using repellent, noting that dengue mosquitoes bite in the daytime and are most active around dusk. TripAdvisor ↗
The Costa Rica kit
- Picaridin 20% travel sprays: odorless in the heat, layers over sunscreen and deters both mosquitoes and beach no-see-ums. One 3.4 oz bottle covers about a week of daily use for one person.
- A full-size backup in the checked bag for a two-week loop or a family, so you're not buying an unknown brand in a beach-town shop.
- Permethrin 0.5% for hiking clothes: treat a long-sleeved shirt, trousers and socks at home 48 hours before you fly. Treated fabric repels and kills insects on contact through several washes, and it is CDC's advice against the forest sand flies that slip through ordinary nets.
One more rule outlasts the trip. Any fever during or after your trip means a doctor visit, and you tell them you were in Costa Rica. Dengue usually shows up within two weeks; malaria can take longer. That one sentence is what gets you the right test quickly.
Traveler questions
What does the chikungunya notice mean for a Tamarindo trip?
Tamarindo is inside the notice area, and July's local outbreak was at Playa Langosta next door. CDC recommends chikungunya vaccination for travelers visiting an outbreak area and advises pregnant travelers to reconsider travel to the affected areas, especially close to delivery. Ask a travel clinic whether the vaccine fits your trip, wear repellent every day from breakfast on, and check the notice again the week before you fly, since it may have been updated.
Do I need malaria pills for Arenal or La Fortuna?
La Fortuna and the Arenal area are in Alajuela, one of the two provinces where the CDC says malaria transmission occurs and lists prevention medicines. The other is Limón, on the Caribbean coast. Whether that adds up to a prescription for your stay is a call for a travel clinic, made with your exact route and dates, 4–6 weeks before departure. Guanacaste, Monteverde, Manuel Antonio and San José are outside those provinces, and there CDC recommends bite precautions only.
Is it safe to visit Costa Rica while pregnant?
CDC advises pregnant travelers to reconsider travel to the areas covered by the chikungunya notice, especially close to delivery. Costa Rica is also on CDC's Zika risk map, and CDC advises pregnant travelers headed to areas with Zika risk to talk to a healthcare provider first. Have that conversation before you book.
What are the itchy bites on my ankles after the beach?
Most likely biting midges, the no-see-ums also called sand flies or sand fleas. They come out at dawn and dusk in still air and leave itchy, delayed welts on ankles and calves. Repellent on the lower legs before a sunset walk, a shower after the beach and beach time in the breezy middle of the day prevent most of them.
Do I need a yellow fever vaccine for Costa Rica?
CDC does not recommend it for Costa Rica. The country does ask travelers aged 9 months and older arriving from a country with yellow fever risk for proof of vaccination, so if you're combining the trip with Colombia or eastern Panama, check whether that rule applies to you.
Is Monteverde buggy?
Usually not. The cloud forest sits at about 1,400 m, cool and breezy, and mosquitoes are scarce next to the lowland beaches. It is outside CDC's malaria provinces. It is in Puntarenas province, so check the CDC map to see whether the chikungunya notice covers it, and keep the daytime repellent habit either way.
Sources
Health authorities, surveillance reports and news coverage of official bulletins used for this briefing, last checked October 2026. Traveler reports are linked where they appear. This page summarizes public-health guidance and is not medical advice.
- CDC Travel Health Notice
- CDC Travel Health Notice
- CDC Travel Health Notice
- delfino.cr
- delfino.cr
- ministeriodesalud.go.cr
- European Centre for Disease Prevention and Control
- ministeriodesalud.go.cr
- infobae.com
- CDC: chikungunya
- CDC: zika
- CDC: zika
- CDC Travel Health Notice
- CDC destination page for travelers
- CDC Yellow Book (earlier edition)
- crhoy.com
- CDC Yellow Book 2026
- Pan American Health Organization (PAHO)