Scrub typhus is a mite-borne disease. The causative organism is Rickettsia orientalis. Wild rodents are the primary host and harbour the disease. People become infected when they walk through cleared areas of jungle or forest and are bitten by infected mites. One to 3 weeks after the mite bite, symptoms of tiredness, chills, severe headache and backache develop. At the site of the mite bite, a slight skin elevation occurs followed by blisters and, finally, a flat black scab. After a 5- to 10-day incubation, there is a sudden fever and severe headache, along with muscle pain, dry cough and swollen lymph nodes. A rash typically spreads over the arms, thighs and torso. Serious neurological symptoms may occur if the disease is not treated.
Scrub typhus occurs primarily among those who work in scrub areas in South-East Asia, northern Australia, India and the western Pacific. The disease is most common among those in scrub lands, forest clearings, or other mite-infested clearings, notably farmers, field workers, hunters and surveyors.
The disease has been known in Japan for over a thousand years. The untreated mortality rate ranged from 30% in Japan to 15% in Malaysia, but is much reduced with antibiotics. The disease can be frequently fatal in old people.