Thailand Mosquito Guide: Dengue, Zika, and How to Protect Yourself

Mosquitoes are the single most significant health risk for travellers in Thailand — not because deaths are common, but because dengue fever affects tens of thousands of people annually and the symptoms (high fever, severe headache, muscle pain, rash) can hospitalise visitors for a week or more and significantly disrupt travel plans. Understanding the risk and applying simple prevention measures dramatically reduces your exposure. Dengue fever: dengue is transmitted by the Aedes aegypti mosquito — a daytime biter that breeds in standing fresh water. It is present throughout Thailand, including in Bangkok, Chiang Mai, and the major tourist islands. There is no specific treatment — management is supportive (rest, fluids, paracetamol — never ibuprofen or aspirin with dengue, as they increase bleeding risk). A dengue vaccine (Dengvaxia) exists but is typically only recommended for people with confirmed prior dengue infection. Peak dengue season corresponds with the wet season (June–October) when standing water is widespread. Zika virus: Zika was reported in Thailand, particularly the south, but current incidence is low. The main concern is for pregnant women — Zika can cause birth defects (microcephaly). Pregnant travellers should consult their doctor before visiting Thailand and consider postponing non-essential travel to active Zika regions. The same Aedes mosquito transmits Zika as dengue. Malaria: malaria risk in Thailand is low in most tourist areas including Bangkok, Chiang Mai, Phuket, Koh Samui, and Krabi. Malaria is present in some forested border regions — particularly near the Myanmar and Cambodia borders. If trekking in Mae Hong Son, Tak Province, or Trat Province rural areas, consult a travel medicine clinic about prophylaxis before departure. The islands (including Koh Chang, Koh Lipe, and southern islands) are generally malaria-free. Protection strategy: DEET-based repellent (30–50% DEET) is the most effective chemical repellent — apply to all exposed skin. Reapply every 3–4 hours, especially during outdoor activity. Picaridin is an alternative for those who dislike DEET's texture. Wear long sleeves and trousers at dusk and in heavily vegetated areas. Use air conditioning when available — Aedes mosquitoes struggle in cold environments. Use mosquito nets in open-air accommodation. Eliminate standing water around your accommodation (check plant pots, water containers). If you develop a high fever, headache, and body aches within 2 weeks of arriving in Thailand — seek medical attention promptly and mention mosquito exposure. Blood tests for dengue are widely available at Thai hospitals and clinics.