Are there mosquitoes in St. Thomas? Yes, but 2026 has been quiet.

Yes. Aedes aegypti, the day-biting mosquito that spreads dengue, lives around homes and town streets on St. Thomas, and the island had 105 confirmed cases in the 2024 outbreak. That outbreak is over, the US Virgin Islands reported no dengue to the CDC in 2026 through late October, and no passport, malaria medicine or yellow fever vaccine is needed, so a cruise day or a villa week calls for a daytime repellent habit and little else.

Dengue: the 2024 outbreak and a quiet 2026

The CDC counts the US Virgin Islands among the places with frequent or continuous dengue risk. The territory's first outbreak since 2012–2013 began on St. Thomas and St. John, and the Virgin Islands Department of Health declared a dengue outbreak in the St. Thomas–St. John district in 2024. A CDC report published in October 2026 counts 105 confirmed cases on St. Thomas between January 2024 and June 2025. Symptoms began in April–June 2024 for 23 of them, July–September for 77 and October–December for 5, and for none from January to June 2025. Three patients were hospitalized.

CDC's notifiable-disease data, updated October 28, 2026, list no dengue cases reported by the USVI in 2026 through the week ending October 24, after 212 plus 4 severe cases in 2024 and 47 in 2025. The same data list one chikungunya case reported from the territory this year, without saying whether it was caught there, and no Zika. There is no malaria, and for yellow fever the CDC says "Vaccine is not recommended." Visitors caught dengue in the outbreak too. Of the 246 travel-associated cases that US residents picked up in US states and territories in 2024, 22.0% came from the USVI, the CDC reported. Our US Virgin Islands briefing covers St. Croix and the territory-wide numbers.

Cruise days and the beaches

A port day is a daylight visit, the hours when Aedes bites, with its first peak in the morning. At Havensight, east of Charlotte Amalie, put repellent on over sunscreen in the cabin, before the walk or taxi to town or the beach. At Crown Bay, on the west side, do the same and pack the bottle for a second coat after swimming. A walk down Main Street needs repellent as much as the beach does, because the dengue mosquito stays close to homes and streets. A passenger ashore from morning to mid-afternoon usually leaves before the late-afternoon no-see-um hours.

On the beaches, the evening biter is the no-see-um, a tiny biting midge that goes for ankles and calves. At Magens Bay it has a reputation for gathering near the sand and scrub-grass line at dusk. Forum posters tend to say the bites start after about 4 pm, that a steady beach wind keeps them away and that mosquitoes surge after heavy rain, and beaches next to salt ponds tend to have more of both. If you stay past 4 pm, spray ankles and calves and sit where the breeze reaches. Villa renters should keep screens shut and check cistern covers, buckets and plant saucers for standing water. Our Barbados sand fly guide explains how the midges behave.

Where you're going

Scores are for a December–April trip.

Taking a day on St. John? Our St. John briefing covers the national park trails and Cinnamon Bay. Starting or ending the cruise in Puerto Rico? See the Puerto Rico briefing.

What travelers report

Paraphrased from a 2012 Cruise Critic thread and an undated TripAdvisor thread, and linked so you can read them in full. Wind and rain change the bites from one day to the next.

• St. Thomas beaches · 2012

  A cruiser asked about bites friends got after swimming on St. Thomas; replies suggested sea lice or sand fleas as the cause, and the friends treated them with calamine lotion and an oral antihistamine instead of scratching. Cruise Critic ↗

• Magens Bay, St. Thomas · mid-June, around 5 pm

  A poster had read about swarms of no-see-ums at dusk near the sand and scrub-grass line at Magens Bay, but their daughter's mid-June wedding ceremony there at about 5 pm had no bug problems, and other guests reported no mosquito trouble either. TripAdvisor ↗

Two habits outlast the trip. Keep using repellent for three weeks after you get home. And if you get a fever, see a doctor and say you were in the US Virgin Islands. That one sentence points the doctor toward a dengue test.

Traveler questions