THAILAND – Thai health authorities warned that tiny mite larvae known as chiggers had sparked a widespread outbreak of scrub typhus, reporting 7,055 infections and six deaths since January 2025.
Invisible danger in the grass
The Department of Disease Control said the larvae of predatory mites, commonly called chiggers, were present across the country and were most often found in damp, shaded areas of forests and high grass. “These mites are tiny, you can hardly see them — but they can be lethal,” said Dr. Monthian Khanasawas, director of the national disease control agency. He warned that the cool season often draws people into the hills to enjoy misty weather, increasing exposure in sites where the parasites hide under leaves and near tree cover.
Outbreak data and hotspots
Officials reported 7,055 confirmed cases this year, a rate of 10.66 infections per 100,000 people, with infections recorded in 74 of Thailand’s 77 provinces. Northern and border provinces were identified as hotspots, including Chiang Mai, Chiang Rai, Mae Hong Son, Ubon Ratchathani and Tak. Health authorities said the number of reported cases was still rising.
How a tiny bite can become deadly
Health experts explained that a chigger larva does not burrow deeply but abrades the skin and secretes digestive enzymes that break down cells. The parasite then feeds on the fluid, while the bacterium Orientia tsutsugamushi is introduced into the body. Symptoms typically began about 10 to 12 days after the bite, with a sudden fever, headache, muscle and joint pain, red eyes and profound fatigue. An eschar — a round, dark crust at the bite site often compared to a cigarette burn — frequently formed, although many victims did not notice the initial sting.
Severe complications and fatalities
“Some patients recover without treatment,” Dr. Monthian said, “but others developed severe complications — pneumonia, meningitis or even multi-organ failure.” Authorities said delayed recognition of symptoms, and confusing early signs with a routine flu, contributed to fatalities. Six people had died from the infection in 2025, the agency reported.
Who is most at risk
Agricultural workers, day labourers and outdoor tourists were singled out as particularly vulnerable because of prolonged time spent in natural vegetation. Officials urged extra caution for anyone planning camping or hiking trips in national parks and rural areas during the cooler months.
Preventive measures for outdoor visitors
The health agency issued clear advice for people visiting forested or grassy areas: wear long sleeves and long trousers, tuck trouser legs into socks, and use insect repellent containing 20–30% DEET. Campers were told not to sit directly on grass or bare earth and to avoid pitching tents in shaded, damp spots. After outdoor activity, authorities recommended immediate showering, hair washing and cleaning clothing with strong detergent, noting that the tiny mites could survive on textiles for several hours.
What to do if symptoms appear
Anyone who developed fever, headache or a skin crust within two weeks of a forest visit was advised to seek medical attention promptly and to mention recent outdoor exposure. The disease is treatable with antibiotics, most commonly doxycycline, and early therapy greatly improved the chances of full recovery. The agency stressed that without timely antibiotic treatment the illness could be fatal.