Tonga's whale season comes after the dengue peak. Check the status anyway.

Are there mosquitoes in Tonga? Yes, including the day-biting Aedes that spreads dengue. Tonga had national dengue outbreaks in 2025 and 2026, both declared over by August, and there is no malaria. A June–September trip, which takes in most of the July–October whale-swim season, comes after the usual dengue peak, so the routine is repellent ashore and a net in any unscreened room.

Two dengue outbreaks in two years

Tonga's health ministry declared a national dengue outbreak on February 19, 2025, with 10 cases among young people, the Pacific news agency PINA reported. The World Health Organization's Pacific surveillance shows weekly reports of dengue-like illness peaking at about 185 in early March 2025, and still running at about 30 a week from late June through July. When the ministry declared the outbreak over on August 20, 2025, RNZ reported 907 cases and 3 deaths, with the last case on August 4.

Dengue came back in April 2026. Cases were confirmed on Tongatapu early in the month, and the ministry declared an outbreak in mid-April. This one was smaller, with dozens of confirmed cases, most on Tongatapu, and no deaths reported. WHO's weekly reports of dengue-like illness peaked in late April, far below the 2025 peak, and fell below 10 a week by early June. A Pacific epidemic alert summary records the outbreak declared over on July 31, 2026, and WHO's reports have stayed near zero since. Tonga has no CDC travel notice and isn't on the CDC's global dengue list.

Both outbreaks started in the hot, wet months, which tend to run from about November to April, and both were over by late August. June to September, the cooler and drier season, comes after that peak, and August and September have been the quietest months. A dengue-free June isn't certain, since 2025's outbreak was still going in June and July. A November–April trip falls in the months when both outbreaks began and peaked, so on a wet-season trip, check the ministry's status closely and keep the daytime routine strict.

Aedes mosquitoes bite in daylight, with peaks after sunrise and in the late afternoon. Ashore in Nuku'alofa, Neiafu or Ha'apai, put repellent on over sunscreen in the morning, again after swimming or snorkeling and before sunset. Our dengue & Zika routine has the full schedule. The CDC also lists Zika, with no current outbreak, so if you're pregnant, talk to a healthcare provider before the trip.

On the water, ashore and at night

Whale-swim and sailing days in Vava'u are spent on the water, away from mosquito breeding sites, and tend to bring few bites. The bites happen ashore, by day and into the evening. In the cooler months a steady breeze tends to keep mosquitoes down, and the usual complaint is a room with no bed net or screens. Ask about nets or screens when you book, check the net for holes on arrival, and pack your own if you're not sure.

The CDC also lists leptospirosis, which isn't spread by insects. Avoid floodwater and wading in fresh water or mud.

Where you're going

How Tongatapu, Vava'u and Ha'apai compare for a June–September trip.

Adding another island stop? Our Fiji, Samoa and American Samoa briefings cover dengue on those islands.

What travelers report

Paraphrased from an older TripAdvisor thread and a resort review and linked so you can read them in full. Neither is dated, and the breeze and your room change the picture.

• Ha'atafu, Tongatapu · August-September

  Asked about mosquitoes in August, a self-described mosquito magnet said they would be waiting but that a steady breeze most days keeps them down, and advised repellent, a mosquito coil and sleeping under a net. Another poster's companion got only a couple of bites. This is an older thread. TripAdvisor ↗

• Tongan Beach Resort, Neiafu (Vava'u)

  In a negative review, a guest complained of many mosquito bites because the bed had no mosquito net; the manager blamed the remote location. TripAdvisor ↗

One rule outlasts the trip. Any fever during or after your trip means a doctor visit, and you tell them you were in Tonga, especially if it comes with headache, rash or body aches in the two weeks after you get home. Our after-bites guide covers the warning signs.

Traveler questions