Travelling to Thailand is not inherently risky, but it’s also important to be aware of certain tropical diseases that can affect visitors, especially in rural or forested areas. One such disease is scrub typhus, a bacterial infection endemic to parts of Asia, including Northern Thailand.
While it is relatively rare among tourists, and more common among those working in agriculture, scrub typhus can be life-threatening if left untreated. A recent case of a woman from the UK who was hospitalised upon her return from Thailand prompted me to write this post and inform my readers of the facts, symptoms, prevention strategies, and what to do if you suspect infection.
What Is Scrub Typhus?
Scrub typhus is an acute febrile illness caused by the bacterium Orientia tsutsugamushi. It is transmitted to humans through the bite of infected chigger mites (larval mites of the Trombiculidae family), often found in rural or forested areas with dense vegetation.
- It is not transmitted person-to-person.
- The bite is typically painless and often goes unnoticed.
- The disease is part of the “typhus group,” but is biologically distinct from epidemic or murine typhus.
Where Is Scrub Typhus Found?
Scrub typhus occurs in a region known as the “tsutsugamushi triangle”, which spans:
- Southeast Asia (including Thailand, Laos, Cambodia, Vietnam, Myanmar)
- South Asia (India, Nepal, Sri Lanka)
- Parts of China, Japan, and Northern Australia
In Thailand, cases are most common in:
- Northern provinces like Chiang Mai and Chiang Rai
- Jungle and highland areas
- During or after the rainy season, typically June to November
How Common Is It?
In Thailand, scrub typhus is one of the most reported rickettsial diseases. According to the Thai Ministry of Public Health, over 10,000 cases are reported annually, though this includes both locals and tourists. The actual number is likely higher due to underreporting and misdiagnosis.
One study using national surveillance data reported the following: Between 2003 and 2018, Thailand reported 103,345 cases of scrub typhus, with a significant increase over time. The disease affected more men than women, particularly agricultural workers, and 72% of cases were in people aged 15–64.
The northern region carried the highest disease burden, accounting for 53% of annual cases. Within this region, Chiang Rai, Chiang Mai, Tak, Nan, and Mae Hong Son made up 84% of northern cases, or 45% of all cases nationwide.
Most cases occurred between June and November, with less seasonality observed in the south. In Chiang Rai province, factors such as elevation, rainfall, temperature, population size, habitat complexity, and land cover diversity were linked to higher incidence (source).
What Are the Symptoms?
Symptoms usually appear 6–21 days after a mite bite. Common symptoms include:
- Sudden high fever
- Headache and body aches
- Swollen lymph nodes
- Rash (often on the trunk)
- Gastrointestinal issues (nausea, vomiting)
- Cough or breathing difficulties
- A key sign is an eschar, which is a dark, scab-like sore at the site of the mite bite, but this is not always present.
In more severe cases, the infection can lead to:
- Lung inflammation (pneumonitis)
- Liver inflammation or jaundice
- Meningoencephalitis
- Multi-organ failure
How Dangerous Is It?
- If treated promptly, most patients recover fully within a few days.
- Without treatment, the disease can be severe, with a mortality rate of 6–20%, depending on access to care.
- The standard treatment is the antibiotic doxycycline, which is widely available in Thailand.
How to Prevent Scrub Typhus
There is no vaccine for scrub typhus, so prevention focuses on avoiding mite bites, particularly in high-risk environments:
Preventive Measures:
- Wear long-sleeved shirts and long trousers when in grassy or forested areas.
- Apply insect repellent with at least 20–30% DEET on exposed skin.
- Treat clothing and gear with permethrin.
- Avoid sitting or lying on the ground or grass.
- Shower and change clothes promptly after outdoor activities.
What to Do If You Suspect Infection
If you experience unexplained fever, swollen glands, rash, or fatigue during or after travel to rural parts of Thailand:
- Seek medical attention immediately.
- Inform the doctor of your travel history, including any forest trekking, hiking, or rural exposure.
- Request testing for tropical fevers if symptoms persist.
- Early antibiotic treatment is crucial and typically leads to rapid recovery.
In Summary
Scrub typhus is treatable and preventable, and while cases do occur – much like malaria in border areas or dengue during rainy season – it needn’t be a major concern if you take sensible precautions. When hiking or visiting rural areas, wear protective clothing, use insect repellent, and choose clean, well-maintained accommodation with basic pest control.
Further Reading & Sources:
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