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Dengue in Thailand — sensible caution, not panic
What this means
Dengue is a mosquito-borne viral illness that is genuinely present in Thailand — not a reason to cancel a trip, but a reason to take repellent seriously in a way many visitors from cooler countries never have. The mosquito that carries it bites during the day, breeds in small containers of clean standing water in cities, and is most active in the rainy months. The response is a short list of habits, plus knowing the few symptoms that mean stop self-treating and see a doctor.
Last reviewed · AraiWa editorial
Decision helper
Quick decision
Buy repellent with DEET, Picaridin or IR3535 and actually use it in the daytime — that single habit is most of the protection. Everything else is refinement.
What changes your plan
A high fever during or shortly after a Thailand stay changes your plan: dengue is on the table, paracetamol-only is the standard self-care caution (avoid ibuprofen and aspirin until a doctor rules dengue out), and warning signs mean a hospital, not the pharmacy.
Common mistake
Saving the repellent for the evening. The dengue mosquito is a daytime biter — dawn, daylight, dusk — which is exactly backwards from the malaria instinct most travellers arrive with.
Local-style move
The habit locals with a garden or balcony have drilled in: no standing water. Tipping out plant saucers, buckets and trays weekly is textbook WHO prevention, and it protects the whole building, not just you.
The risk, in proportion
Dengue circulates in Thailand year-round, with pressure rising in the rainy months when its mosquito breeds everywhere water collects. Most infections are mild or unnoticed; a minority become the feverish, exhausting illness people mean by 'dengue'; a small minority of those progress to severe dengue, which is a medical emergency. That gradient is the whole logic of this page: cheap prevention because infection is common enough to matter, and sharp attention to warning signs because the severe form is rare but serious.
Prevention that actually works
- Repellent on exposed skin during the day — WHO lists DEET, Picaridin (icaridin) and IR3535 as the effective ingredients. Sold in every Thai pharmacy and convenience store.
- Cover up where practical: long sleeves and trousers in mosquito-heavy settings, particularly gardens, older neighbourhoods and anywhere near stagnant water.
- Deny the mosquito its nursery: empty or scrub anything holding standing water around where you stay — plant saucers, buckets, unused containers — weekly.
- Screens, air conditioning and (for daytime sleepers, including anyone already ill) mosquito nets all reduce bites indoors.
If you get a fever
- Sudden high fever with headache, pain behind the eyes, muscle and joint aches or a rash during or within two weeks after time in Thailand: dengue is plausible — see a doctor and say where you have been. Testing is routine in Thai hospitals.
- Standard self-care caution while dengue is unconfirmed: fluids, rest, paracetamol for fever — and avoid ibuprofen and aspirin, which are discouraged in dengue because of bleeding risk.
- Warning signs per WHO — severe abdominal pain, persistent vomiting, bleeding gums or nose, blood in vomit or stool, extreme lethargy or restlessness — mean severe dengue is possible: go to a hospital immediately. These often appear just as the fever seems to break.
- A second dengue infection carries a higher risk of severe illness than the first — anyone who has had dengue before should be quicker, not slower, to get a fever checked.
Related guides
Dengue season and the rainy season are the same calendar — the rainy season guide covers what those months look like beyond the mosquitoes. If a fever does send you to a doctor, healthcare in Thailand explains what a hospital visit costs and how public and private differ, and the numbers to call in a genuine emergency are in the emergency numbers guide.
Sources & further reading
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