Guam's last local dengue was in 2019. Its day-biting mosquito is still around.
CDC counted 13 locally acquired cases in that outbreak, the first since 1944, and the two cases confirmed in 2025 were caught off-island. The Asian tiger mosquito bites by day, so the routine is repellent for gardens, Ritidian's forest and the southern waterfall hikes.
Are there mosquitoes in Guam? Yes, including the Asian tiger mosquito, a daytime biter that can spread dengue. Local dengue is rare here, with one small outbreak since 1944, in the fall of 2019, and the two cases confirmed in 2025 were caught elsewhere. There is no malaria, so a daytime repellent habit for hikes and gardens covers most trips.
One local outbreak since 1944
CDC's 2023 review of dengue in US territories rates the risk on Guam as sporadic or uncertain. Guam isn't on CDC's global dengue list and has no CDC travel notice. CDC counted 45 cases reported on Guam from 1988 to mid-2019, all caught elsewhere, most often in the Philippines.
That changed in September 2019. CDC's Morbidity and Mortality Weekly Report describes the first locally acquired case since 1944, detected on September 10, and the Government of Guam declared a state of emergency three days later. From September 9 to November 25, 249 suspected cases were identified and 17 confirmed, 13 of them caught on Guam and 4 linked to travel. Two were hospitalized. The cases clustered in the more densely populated north and center of the island, which includes Tumon and Hagåtña.
In 2025, the Department of Public Health and Social Services confirmed two, in September and late October, and judged both patients to have been infected before they reached Guam, Isla Public Media and the Guam Daily Post reported. The newest case reports are from October 2025. With dengue not endemic, the risk mostly depends on whether an imported case starts local spread, so check the department's news before you fly.
The tiger mosquito and where it bites
The mosquito CDC names on Guam is the Asian tiger mosquito, Aedes albopictus, and Guam's health department identifies it as the species that spreads dengue there. It breeds in small pockets of water: tree holes, coconut shells, bromeliads, water barrels, trash, gutters, tarps and tires. It bites in daylight, with peaks in the morning and late afternoon, and numbers tend to rise after rain. Our Japan briefing covers the same species in Tokyo and Kyoto.
Bites are likeliest in gardens, on forest trails and on waterfall hikes, typical tiger mosquito habitat. That points to Ritidian's limestone forest in the north and the river and waterfall trails around Umatac and Inarajan in the south. Tumon Bay's beachfront hotels are air-conditioned and tend to be light. Before a hike, put repellent on over sunscreen, then reapply after swimming and again before sunset. Our dengue & Zika routine has the full schedule.
CDC lists Guam among areas with mosquitoes that can spread Zika but no reported Zika cases, and for those areas it advises pregnant travelers to prevent mosquito bites during and after travel. CDC also lists leptospirosis, which isn't spread by insects. Avoid floodwater and wading in fresh water or mud.
When to go
The drier months, roughly January to May, tend to be the easier stretch. The wet season runs roughly July to November. The 2019 outbreak's local cases began between early September and mid-November, and both 2025 imported cases were reported in September and October.
Where you're going
How the main areas compare across the year.
Tumon Bay & Two Lovers Point
Air-conditioned beachfront hotels in the north-central part of the island, where the 2019 local cases clustered. No local dengue has been found since, and a morning spray covers the gardens and pool deck.
Hagåtña
The capital, in central Guam, with the same low dengue picture as Tumon. Yards and gardens are tiger mosquito habitat, so daytime repellent applies in town too.
Ritidian Point
Beach and limestone forest at the island's northern tip, inside the Guam National Wildlife Refuge. The forest trails are likely to have day-biting mosquitoes, so spray before you leave the car.
Umatac, Inarajan & the southern hikes
Rural, greener and wetter, with river and waterfall trails that are likely to bring more bites. Repellent at the trailhead, and skip wading in muddy fresh water because of leptospirosis.
Island-hopping? Our Saipan and Palau briefings cover the neighbors. Palau has had more dengue than Guam.
The Guam kit
- Picaridin 20% travel sprays: odorless in the heat, layers over sunscreen and easy to reapply after a swim at Tumon. One 3.4 oz bottle covers about a week of daily use for one person.
- Permethrin 0.5% for hiking clothes: treat a long-sleeved shirt and light pants at home 48 hours before you fly. It goes on fabric only, never on skin.
One rule outlasts the trip. Any fever during or after your trip means a doctor visit, and you tell them you were in Guam, especially if it comes with headache, rash or body aches in the two weeks after you get home. A US territory is easy to leave out of a travel history, so say it out loud.
Traveler questions
Is there dengue in Guam right now?
Not locally, as far as public reports show. Guam's only local outbreak since 1944 was in 2019, when CDC counted 13 locally acquired cases. In 2025, Guam's Department of Public Health and Social Services confirmed two cases and judged both to have been infected before the patients arrived, according to local news reports. The newest case reports are from October 2025. Check the department's news before you fly, and wear daytime repellent on hikes.
Do I need malaria pills or a yellow fever vaccine for Guam?
No. CDC lists no malaria for Guam and recommends no malaria medicine. The yellow fever vaccine is not recommended, and Guam doesn't require it for entry.
Is it safe to visit Guam while pregnant?
CDC lists Guam among areas with mosquitoes that can spread Zika but no reported Zika cases. For those areas, CDC advises pregnant travelers to prevent mosquito bites during and after travel. That means daytime repellent, covered skin on trails and an air-conditioned or screened room.
Are there mosquitoes at the Tumon Bay hotels?
Some, though rooms are likely to be quiet. Tumon's beachfront hotels are air-conditioned, and the tiger mosquito tends to stay around gardens, shade and standing water. It bites in daylight, so put repellent on before a garden breakfast, an afternoon by the pool or a visit to Two Lovers Point.
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.