Are there mosquitoes on Oahu? Few in Waikiki, plenty at Manoa Falls.

Yes, though Waikiki sees few of them. Oahu's dengue mosquito is the day-biting Asian tiger mosquito, and it is thickest in the wet rainforest valleys behind Honolulu, with Manoa Falls the best-known example. The trip needs no vaccine or medicine, only repellent on the right walks, and our Hawaii briefing covers the other islands.

Why Oahu watches for dengue

Dengue isn't endemic in Hawaii. The state Department of Health says it currently sees cases only in travelers who caught it elsewhere, and Oahu is where most of them turn up. CDC's provisional weekly tables listed 9 dengue cases reported by Hawaii in 2026 through mid-October, against 13 at the same point in 2025, none of them severe. Press reports of health department figures put most of this year's cases on Oahu, and all of them involved travel to Pacific islands.

The concern is what happens next. A traveler who arrives sick and gets bitten can pass the virus to local mosquitoes. Oahu's last local spread was a 2011 outbreak. In the 2001–02 outbreak, 26 local infections were on Oahu, and 20 of them were in two neighboring windward communities with thick vegetation and more than 70 inches (177 cm) of rain a year, four times Honolulu's, a 2005 study in Emerging Infectious Diseases found. Honolulu's 1943–44 epidemic was spread by Aedes aegypti, later eliminated from Oahu, which leaves the tiger mosquito as the island's dengue mosquito. Researchers trapped it in Manoa in 2023–24.

For a visitor, that comes down to two habits. Repellent goes on by day before valley and garden walks, since the tiger mosquito bites in daylight, with peaks in the morning and late afternoon. And if you arrive from a Pacific island with dengue, or a fever starts during your stay, see a doctor and say where you've been. Keeping bites down while you're sick also keeps Oahu's mosquitoes from picking up the virus. Our dengue routine has the daily schedule. Hawaii has no malaria and no documented local West Nile, and no local Zika or chikungunya has been reported.

Light in Waikiki, heavy at Manoa

Waikiki, the Honolulu waterfront and the leeward resort coast tend to see few bites. The southern house mosquito, a Culex, comes out at dusk, so an evening coat of repellent covers a lanai drink or an outdoor dinner. The Diamond Head crater trail tends to be dry and exposed, with little shade or standing water, so sun is likely the bigger issue there.

Manoa Falls is the exception. The trail climbs a wet rainforest valley minutes from Waikiki, and visitors tend to describe mosquitoes from the parking lot on, thickest along the stream. The Lyon Arboretum sits in the same valley, and other wet valley and windward trails behind Honolulu tend to be similar. Put repellent on before you leave the car, reapply if you sweat it off, and wear light long pants. Stay out of the pool at the falls and other streams, especially with cuts or scrapes. State health advice, as reported in local media, warns of leptospirosis in fresh water, and repellent does nothing for that one.

Waikiki works in any month. Rain drives the biting on the trails, so Manoa and the windward valleys tend to be buggiest after a wet spell and in the wetter months, roughly November to March. Dengue has no local season. This year's Oahu cases were announced from February through October, according to press reports, as imports followed outbreaks elsewhere in the Pacific.

Where you're going

How the main stops compare, in any month.

Heading to Kauai too? Our Kauai briefing covers the Kalalau Trail and the wetter north shore.

What travelers report

Paraphrased from a TripAdvisor review and linked so you can read it in full. It isn't dated, and rain and shade change the picture on the valley trails from one day to the next.

• Manoa Falls, Honolulu

  A reviewer headlined their Manoa Falls review "Worst mosquito infested hike ever!". TripAdvisor ↗

One rule outlasts the trip. Any fever during or after your trip means a doctor visit, and you tell them you were on Oahu, and anywhere else you went.

Traveler questions