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Preliminary Conclusions

Scrub typhus is the oldest known vectorborne infection, and until recently, has almost exclusively been reported from certain regions within the Asia-Pacific region (the tsutsugamushi triangle), where it is caused by Orientia tsutsugamushi (2). In that region, approximately 1 million cases are reported each year, with a case fatality rate of approximately 7% if not adequately treated (2). Scrub typhus was recently discovered in southern Chile (3), occurring over a geographic range of almost 1,240 miles (2,000 km) from the Biobío Region in central Chile to Tierra del Fuego in the south. Molecular analyses have identified a novel Orientia species (Candidatus Orientia chiloensis) as the causative pathogen (4). Vector studies in the Los Lagos and Aysén regions suggested larval trombiculid mites of the genus Herpetacarus (commonly known in the United States as chiggers) as disease vectors (5).

Understanding the reasons for the observed increase in scrub typhus cases requires further eco-epidemiologic studies. Scrub typhus in Chile displays a marked seasonality, with 97% of cases to date occurring during the austral summer months of December–March (Chilean Rickettsia and Zoonosis Research Group, unpublished data, January 2023). Apart from climatic factors, the outbreak might also be related to an increase in outdoor activities after 2 years of pandemic restrictions as well as growing awareness of the disease, resulting in increased testing and reporting. Because of its nonspecific clinical characteristics, scrub typhus might be easily overlooked, and diagnosis requires a high index of suspicion. Rapid diagnosis and treatment, however, are crucial to avoid severe disease and possible complications, such as pneumonia, renal failure, and meningoencephalitis. If infection is suspected, treatment with doxycycline should be initiated without delay (2).

Exposure to trombiculid mites is associated with outdoor activities and affects not only residents of rural areas, but also travelers on camping and trekking trips. The growth of ecotourism in southern Chile has increased the importance of raising awareness among physicians worldwide who see ill travelers returning from the region. No vaccine is available to prevent scrub typhus; to prevent exposure to mites, travelers should avoid contact with lower vegetation and soil, wear long sleeves and pants, treat boots and clothing with the insecticide permethrin (0.5%), and use insect repellents containing DEET or other active ingredients registered by the Environmental Protection Agency for use against chiggers, on exposed skin and clothing (2).

Source of original article: Centers for Disease Control and Prevention (CDC) / MMWR (Journal) (
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