Argentina's summer is its dengue season. The last one was quiet.
Buenos Aires came through a record 2024 and a much quieter 2025/26 season. Iguazú Falls carries a CDC yellow fever vaccine recommendation, and Patagonia's early-summer pest is a horsefly that forum regulars say repellent won't stop.
Yes, mainly in Buenos Aires and at Iguazú Falls during the southern summer, which is also Argentina's dengue season. For a December–April trip, plan on daytime repellent from February and a travel-clinic check if Iguazú is on the route. Patagonia and Mendoza carry no meaningful mosquito-borne disease risk.
Buenos Aires, from a record year to a quiet one
Dengue in Argentina comes in seasonal epidemics across the north and center, Buenos Aires included, in the southern summer and autumn. In 2024 the Pan American Health Organization counted 581,559 cases, the second most in the Americas after Brazil. PAHO reported 8,111 confirmed cases in 2025, peaking in early April, and the 2025/26 season ran below the same weeks of the three previous seasons. Argentine press reports in July put its total at fewer than 100 laboratory-confirmed cases.
Chikungunya was the bigger story in 2026. An outbreak centered on Salta, Tucumán and Jujuy in the northwest peaked in April, and PAHO counted 3,803 laboratory-confirmed cases nationwide through late September. Cases also turned up in Buenos Aires province and the city. The CDC says chikungunya vaccination is generally not recommended for Argentina.
Surveillance for the 2026/27 season began in August, and in October PAHO warned that South America's peak season is approaching as El Niño strengthens. Risk in Buenos Aires and Iguazú usually builds from February and peaks in March and April. The dengue mosquito bites by day, with peaks after sunrise and in the late afternoon, so from February on, put repellent on before a day of walking the city. Our dengue & Zika daily routine has the full schedule.
Iguazú Falls and the yellow fever vaccine
Iguazú Falls is in Misiones province, and the CDC recommends yellow fever vaccine for all travelers 9 months and older going to Misiones and Corrientes. Its Brazil page makes the same recommendation for the Brazilian side of the falls. Argentina does not require the vaccine for entry, and the CDC lists no malaria anywhere in the country.
What we suggest you do with this: if Iguazú is on the route, book a travel-medicine appointment 4–6 weeks before departure. The CDC does not recommend the vaccine for travel limited to other provinces, including Buenos Aires, Mendoza and Patagonia. Our Brazil briefing covers the other side of the falls.
The falls are also the buggiest stop on a typical Argentina trip. Expect mosquitoes on the jungle trails and around the hotels, most active in the mornings and evenings. Put repellent on before the trails and again in the late afternoon, and keep hotel windows closed at night.
Patagonia's tábanos, and Mendoza
Patagonia has no mosquito-borne disease of concern and no CDC vaccine or medicine recommendations. Its early-summer pest is the tábano, a large horsefly. Tábanos have a reputation for showing up on both sides of the Argentina–Chile border from late December to mid-January, mostly near lakes and in humid forest around Bariloche and Torres del Paine, on warm, still days. Forum regulars say repellent doesn't stop them, so cover up with long sleeves and light-colored clothing. Not every trip meets them.
Mendoza tends to be light on bites. It was not among the provinces reporting chikungunya in 2026, and the CDC recommends neither yellow fever vaccine nor malaria medicine there.
Where you're going
Buenos Aires
A record dengue year in 2024, then a minimal 2025/26 season, with some chikungunya cases in the city and province. No malaria and no yellow fever vaccine recommended. Wear daytime repellent from February on.
Iguazú Falls & Puerto Iguazú
In Misiones, where the CDC recommends yellow fever vaccine, so this stop belongs at the travel clinic. Expect mosquitoes on the jungle trails and around hotels in the mornings and evenings.
Patagonia: Bariloche, El Calafate, El Chaltén & Ushuaia
No mosquito-borne disease of concern and no CDC vaccine or medicine advice. Lakeshores and humid forest can have tábano horseflies from late December to mid-January.
Mendoza
Mendoza tends to be light on bites. The CDC recommends neither yellow fever vaccine nor malaria medicine here.
The Argentina kit
- Picaridin 20% travel sprays: odorless, layers over sunscreen and easy to split between a city daypack and the Iguazú trails. 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 family or a late-summer trip that includes Iguazú.
- Light-colored long sleeves for lake hikes from late December to mid-January, since forum regulars say spray doesn't stop tábanos.
One rule outlasts the trip. Any fever during or after your trip means a doctor visit, and you tell them you were in Argentina, including whether Iguazú or the north was on the route.
What travelers report
Paraphrased from forum threads 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.
- Iguazú National Park · March
Posters said mosquitoes are most active in the morning and evening and at night in hotel rooms. They advised DEET repellent reapplied often, keeping windows closed at night and bringing repellent from home, and named dengue as the main mosquito-borne concern. TripAdvisor ↗
- Patagonia (Argentina and Chile) · late December to mid-January
A poster said tábanos (horseflies) are found on both sides of the border from late December to mid-January. Fodor's ↗
- Bariloche and El Chaltén · November to February
Replies conflicted: one poster who visited Bariloche and southern Patagonia about five times between November and February never saw a horsefly, while another described El Chaltén in mid-December as overrun with horse flies and fruit flies. TripAdvisor ↗
Traveler questions
Do I need a yellow fever vaccine for Iguazú Falls?
The CDC recommends it for all travelers 9 months and older going to Misiones province, where the falls are, and to Corrientes. Its Brazil page makes the same recommendation for the Brazilian side of the falls. Argentina does not require the vaccine for entry, and the CDC does not recommend it for a trip limited to Buenos Aires, Mendoza or Patagonia. Book a travel clinic 4–6 weeks before departure to talk it through.
Is there dengue in Buenos Aires right now?
The last season was very quiet, after a record 2024. Surveillance for the 2026/27 season began in August, and in October the Pan American Health Organization warned that South America's peak season is approaching as El Niño strengthens. Risk usually builds from February and peaks in March and April, so check current reports before you fly and wear daytime repellent in the city late in the summer.
Do I need malaria pills for Argentina?
The CDC lists no malaria transmission areas in Argentina and recommends no malaria medicine for any part of the country. The travel-clinic question for Argentina is the yellow fever vaccine, mainly if Iguazú or elsewhere in Misiones or Corrientes is on your route.
What are the big flies at Patagonian lakes?
Most likely tábanos, large horseflies. They have a reputation for appearing on both sides of the Argentina–Chile border from late December to mid-January, mostly near lakes and in humid forest on warm, still days. They carry no disease concern, but forum regulars say repellent doesn't stop them, so long sleeves and light-colored clothing are the usual advice.
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.