Cambodia is in a dengue epidemic year. Here's the routine from Angkor to Koh Rong.
Dengue cases in 2026 are more than double last year's, and the mosquito that spreads it bites in daylight, temple hours included. CDC reports no or negligible malaria in Phnom Penh, Siem Reap and the main Angkor Wat complex.
Cambodia has mosquitoes in every month, and in 2026 they matter more than usual. The country is in a dengue epidemic year, with 110,850 cases by early October, and the mosquito that spreads it bites in daylight, temple hours included. Malaria is a narrower question, since CDC reports "no (or negligible) malaria transmission" in Phnom Penh, Siem Reap and at the main temple complex at Angkor Wat.
2026 is a dengue epidemic year
Cambodia is on CDC's global dengue list, a Level 1 notice. The World Health Organization's Western Pacific office, reporting figures from Cambodia's national dengue surveillance system, counted 110,850 cases and 118 deaths by October 4, 2026, against 46,492 cases at the same point in 2025. That is 138% above a year that was itself more than three times 2024. Weekly cases have fallen since a peak in late August but were still far above the epidemic threshold in early October. WHO's figures are national, with no breakdown for Siem Reap or Phnom Penh.
The dry season, roughly December to April, is usually the easier time to visit, and July to September the hardest. This year the epidemic may still be winding down in December, so plan on daytime repellent whatever month you go.
The Aedes mosquitoes behind dengue bite by day, with peaks after sunrise and in the late afternoon, the same hours as the classic sunrise and sunset temple visits. Put repellent on over sunscreen before you leave for a sunrise at Angkor Wat, reapply through a day of temple-hopping, and again before dusk. Air-conditioned or screened rooms cover the night. Our dengue & Zika daily routine has the full schedule.
Angkor, the islands and the malaria line
CDC's Cambodia page says malaria is "primarily isolated to pockets in rural and forested areas," with "rare cases in non-forested areas." It reports "no (or negligible) malaria transmission" in the cities of Phnom Penh and Siem Reap and "at the main temple complex at Angkor Wat," and lists prevention medicine only for "rural and forested areas."
The wording leaves gaps. CDC doesn't say whether outlying forest temples such as Phnom Kulen, Kbal Spean, Beng Mealea and Koh Ker count as rural and forested, and it doesn't name the coast. The forested islands, and the Bokor hills above Kampot, could fall under that wording.
What we suggest you do with this: if your plans include the outlying temples, jungle treks, rural homestays or the forested islands, book a travel-medicine appointment 4–6 weeks before departure and bring the exact route. Ask about Japanese encephalitis vaccine at the same visit. CDC recommends it for stays of a month or more and suggests considering it for shorter trips with rural stays, camping or unscreened nights. Our malaria-zone checklist covers the rest.
Where you're going
The coast is where bites get annoying, with sand flies on Koh Rong's beaches at dawn and dusk, worst where trash collects on the sand. Our sand fly guide covers beach biters in more detail.
Siem Reap & Angkor
CDC reports no (or negligible) malaria in Siem Reap and at the main Angkor Wat complex; outlying forest temples aren't covered by that wording. Put repellent on before you leave for sunrise, because dengue mosquitoes bite in daylight and peak after sunrise.
Phnom Penh
No (or negligible) malaria, per CDC. Dengue is epidemic nationally, and evening mosquitoes are likely at guesthouses and outdoor restaurants.
Kep, Kampot, Koh Rong & Koh Rong Samloem
Sand flies are a frequent Koh Rong complaint, worst at dawn and dusk. CDC's malaria wording doesn't name the coast, and the forested islands and Kampot's Bokor hills could count as rural and forested.
The Cambodia kit
- Picaridin 20% travel sprays: odorless in the heat, layers over sunscreen for long temple days and is easy to aim at ankles on the beach. One 3.4 oz bottle covers about a week of daily use for one person.
- Permethrin 0.5% for clothes: treat a long-sleeved shirt and light trousers at home 48 hours before you fly. Treated fabric repels and kills mosquitoes on contact through several washes, which helps at outlying temples and on rural evenings.
What travelers report
Paraphrased from forum threads and reviews and linked so you can read them in full. None is dated and some may be several years old, so weather, season and where you stay can change the picture.
- Angkor Wat at sunrise and sunset · July
Asked about mosquitoes at Angkor at dawn and dusk, posters said bites were not a major problem on a July sunset visit; the advice was to use repellent and cover up. TripAdvisor ↗
- Long Beach (SokSan), Koh Rong
A reviewer described heavy swarms of sand flies at SokSan Beach and linked them to garbage on the sand. TripAdvisor ↗
- The Royal Sands Koh Rong
A guest said the resort's beach was full of trash and sand flies. TripAdvisor ↗
- Koh Rong
In a thread asking whether Koh Rong is still worth it despite sand fleas, some posters found the bites more of an itch than a real problem, and recommended coconut oil, DEET repellent and mosquito coils for sleeping. TripAdvisor ↗
Heading on? Our Vietnam briefing covers a dengue year concentrated in the south, and our Thailand briefing covers CDC's malaria advice there, which centers on the provinces bordering Myanmar, Cambodia and Malaysia. If you're pregnant, review CDC's Zika guidance before you book, because CDC lists Zika among the diseases for travelers to Cambodia, including spread from a pregnant woman to her baby. And any fever during or after your trip means a doctor visit, and you tell them you were in Cambodia.
Traveler questions
Do I need malaria pills for Angkor Wat?
CDC reports "no (or negligible) malaria transmission" at "the main temple complex at Angkor Wat" and in the cities of Siem Reap and Phnom Penh, and lists prevention medicine only for "rural and forested areas." It doesn't say whether outlying forest temples such as Phnom Kulen, Kbal Spean, Beng Mealea or Koh Ker count. If they're on your list, or you're adding jungle treks, rural homestays or the forested islands, take the route to a travel clinic 4–6 weeks before departure.
Is the dengue epidemic still going?
It was in early October 2026. The World Health Organization counted 110,850 cases and 118 deaths by October 4, more than double the same point in 2025. Weekly cases have dropped since the late-August peak but remain far above the epidemic threshold, and the epidemic may still be winding down in December. Either way, the routine is the same: repellent from the first temple of the morning, reapplied through the day and before dusk.
What are the bites on Koh Rong's beaches?
Sand flies are a frequent complaint in Koh Rong reviews, worst at dawn and dusk and where trash collects on the beach. Put repellent on your ankles and lower legs, and don't lie directly on the sand at those hours. A lounger and a cleaner stretch of beach help.
Do I need a yellow fever vaccine for Cambodia?
CDC does not recommend it, and Cambodia doesn't require it for direct travel from the United States. Cambodia does require proof of vaccination from travelers aged 1 and older arriving from a country with yellow fever risk, including airport transits or layovers of more than 12 hours there, so check the rule if your route passes through such a country first.
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.