Scrub typhus is endemic to a part of the world known as the “tsutsugamushi triangle”,
which extends from northern Japan and far-eastern Russia in the north, to northern
Australia in the south, and to Pakistan in the west (12).
Scrub typhus is essentially an occupational disease among rural residents in the
Asia-Pacific region. In oil-palm workers in Malaysia, the incidence of antibodies to
scrub typhus declines with declining grass density between the rows of maturing
oil-palm. This correlates with the decline of chigger populations in this habitat (4).
An increased in the prevalence of scrub typhus has been reported from some Asian
countries, which coincides with the widespread use of β-lactam antimicrobial drugsScrub typhus is difficult to recognize and diagnose because the symptoms and
signs of the illness are often non-specific. The non-specific presentation and lack of
the characteristic eschar in 40% patients makes the misdiagnosis and underreporting
of scrub typhus common. On the other hand, diagnostic facilities are not available in
much of its native range. Therefore, the precise incidence of the disease is unknown.
An estimated one billion people are at risk for scrub typhus and an estimated one
million cases occur annually (14). Mortality rates in untreated patients range from
0-30%.
The characteristic feature of an outbreak of scrub typhus are: (i) the obvious
association with certain types of terrain; (ii) the marked localization of many cases
within certain small foci; (iii) the large percentage of susceptible people, who may
be infected simultaneously following exposure over relatively short periods; (iv) the
absence of a history of bites or attack by arthropods (15).