Dengue reached all three US Virgin Islands in 2024. Here's this winter's routine.

For American travelers the US Virgin Islands are the easy Caribbean trip. US citizens visit without a passport, there is no malaria, and no yellow fever vaccine is needed. That leaves one mosquito-borne disease to plan for. The CDC lists the territory among the places with frequent or continuous dengue risk, and from January 2024 to June 2025 the islands had their first dengue outbreak since 2012–2013. Cases fell sharply in 2025. The routine that handles dengue is short, and it shifts a little between a St. Thomas cruise day, a St. John hike and an evening on a St. Croix beach.

The 2024–25 outbreak, by the numbers

A CDC report published in October 2026 counted 263 confirmed dengue cases in the territory between January 2024 and June 2025: 118 on St. Croix, 105 on St. Thomas and 40 on St. John. Fifteen patients were hospitalized and one died, the territory's first dengue death since 2005. St. Croix's count rose late in 2024 and into early 2025, and an outbreak was declared there in February 2025. In March 2025 a CDC health advisory said transmission remained high in Puerto Rico and the USVI.

The Virgin Islands Department of Health's 2025 annual report, published in April 2026, counts by calendar year. It recorded at least 215 cases in 2024 and 47 in 2025, with the early-2025 cases all on St. Croix. The CDC and the health department count over different periods and with different case definitions, so their figures don't line up exactly. Either way, 2025 was far quieter than 2024. For 2026 numbers, check the health department's epidemiology data dashboard before you go.

The outbreak reached visitors too. In 2024 the USVI accounted for 22% of travel-associated dengue among travelers to US jurisdictions, according to CDC data. Chikungunya, which the same mosquito spreads, has not spread locally in any US state or territory since 2019, the CDC says.

The daytime routine

Dengue's mosquito, Aedes aegypti, lives around homes and towns, breeds in small pools of standing water and bites in daylight, with peaks in the early morning and late afternoon. Evening-only caution misses most of its hours. Any EPA-registered repellent with picaridin 20%, DEET 20–30%, oil of lemon eucalyptus (OLE) or PMD 30%, or IR3535 does the job. Our dengue & Zika daily routine has the full schedule. On these islands it comes down to three habits.

At night, sleep in an air-conditioned or screened room and keep the doors closed. Villa renters can do one more thing. Tip out standing water around the property, from plant saucers to buckets, because that is where Aedes breeds.

St. Thomas on a cruise day

Charlotte Amalie is a daytime port, and daytime is when the dengue mosquito bites. St. Thomas had 105 of the outbreak's confirmed cases, the second-highest count of the three islands. Put repellent on before you leave the ship, reapply after swimming, and you've covered the port day. Bites are likely to be occasional on a short visit. The dengue mosquito tends to stay close to homes and town streets, so a walk through town calls for repellent as much as the beach does.

St. John: trails and Cinnamon Bay

St. John had 40 confirmed cases in the CDC count, and its trails and shaded bays mean more time outdoors. The trails of Virgin Islands National Park tend to hold more mosquitoes than the open beaches, and mangrove and salt-pond edges are likely spots for midges, so a hike tends to bring more bites than a beach day. Treat a long-sleeved shirt, light trousers and socks with permethrin at home and let them dry before you fly. Permethrin goes on fabric only, never on skin. Repellent goes on exposed skin at the trailhead, and again after the swim at the end of the walk.

Camping at the Cinnamon Bay campground puts you outdoors through dawn and dusk, the hours when midges bite most. Bring treated clothes, put repellent on your lower legs before sunset, and keep your shelter closed from dusk.

St. Croix beaches at dusk

St. Croix had the most cases in the outbreak, 118, and all of the early-2025 cases, so the daytime routine matters most here. The evening complaint on its beaches is no-see-ums, the biting midges also called sand flies. They come out at dawn and dusk, bite the ankles and lower legs, and are worse on calm days and after rain. They are weak fliers, and a steady breeze keeps them grounded, so pick a breezy spot over a sheltered one at sunset. Spray your feet, ankles and calves before you head down to the water, and wear light long pants for a beach-level dinner. Our Barbados sand fly guide explains the insect in more detail.

Where you're staying

Dengue risk is similar on all three islands. The bite nuisance changes with the setting. Here is how they compare for a winter trip.

Winter is the breezier, drier season

Mosquito numbers in the Virgin Islands generally rise in the wet season, roughly late summer and autumn. December to April is drier and breezier, and it usually brings fewer mosquitoes. More wind also means more evenings when the midges stay grounded.

Dengue keeps going through the drier months, though. The St. Croix outbreak was declared in February, in the middle of the winter season. Pack the same repellent for a February trip that you would for September.

What travelers report

Paraphrased from forum threads, some of them several years old, and linked so you can read them in full. Weather, wind and where you stay change the picture from one trip to the next.

• Cinnamon Bay campground, St. John · February · 2016

  Replies to someone planning a February 2016 camping trip were mixed: one said bugs are manageable and mostly a problem after heavy rain, another reported many bites even through clothing. Advice was to stay off the beach at dawn and dusk, keep sand out of living spaces, use DEET and cover up, and one expert said the breezier winter months help. TripAdvisor ↗

• 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 ↗

• St. John · February to early April

  A forum poster said February, March and early April are the driest and most mosquito-free months on St. John. TripAdvisor ↗

• St. Croix · Late November

  Replies to a December traveler said no-see-ums are mostly active at dawn and dusk on the beach and recommended DEET repellent morning and evening. A visitor from late November said the only real problem was by the water at dusk and for a little after. TripAdvisor ↗

Two habits outlast the trip. Keep preventing mosquito bites for three weeks after you get home. And any fever during or after your trip means a doctor visit, and you tell them you were in the US Virgin Islands. A trip that needed no passport is easy to leave out of the conversation, so say it out loud. That one sentence points the doctor toward a dengue test.

Traveler questions