Abstract
BackgroundScrub typhus is an endemic disease in Asia. It has been a rural disease, but indigenous urban cases have been observed in Seoul, South Korea. Urban scrub typhus may have a significant impact because of the large population.MethodsIndigenous urban scrub typhus was epidemiologically identified in Seoul, the largest metropolitan city in South Korea, using national notifiable disease data from 2010 to 2013. For detailed analysis of clinical features, patients from one hospital that reported the majority of cases were selected and compared to a historic control group. Chigger mites were prospectively collected in the city using a direct chigger mite-collecting trap, and identified using both phenotypic and 18S rDNA sequencing analyses. Their infection with Orientia tsutsugamushi was confirmed by sequencing the 56-kDa antigen gene.ResultsEighty-eight cases of urban scrub typhus were determined in Seoul. The possible sites of infection were mountainous areas (56.8%), city parks (20.5%), the vicinity of one’s own residence (17.0%), and riversides (5.7%). Eighty-seven chigger mites were collected in Gwanak mountain, one of the suspected infection sites in southern Seoul, and seventy-six (87.4%) of them were identified as Helenicula miyagawai and eight (9.2%) as Leptotrombidium scutellare. Pooled DNA extracted from H. miyagawai mites yielded O. tsutsugamushi Boryong strain. Twenty-six patients from one hospital showed low APACHE II score (3.4 ± 2.7), low complication rate (3.8%), and no hypokalemia.ConclusionsWe identified the presence of indigenous urban scrub typhus in Seoul, and a subgroup of them had mild clinical features. The chigger mite H. miyagawai infected with O. tsutsugamushi within the city was found. In endemic area, urban scrub typhus needs to be considered as one of the differential febrile diseases and a target for prevention.
Highlights
Scrub typhus, known as tsutsugamushi disease, is a mite-borne infectious disease that is endemic in a triangular geographic region containing the Indian subcontinent, northern Australia and the Far East
Indigenous urban scrub typhus was epidemiologically identified in Seoul, the largest metropolitan city in South Korea, using national notifiable disease data from 2010 to 2013
Eighty-seven chigger mites were collected in Gwanak mountain, one of the suspected infection sites in southern Seoul, and seventy-six (87.4%) of them were identified as Helenicula miyagawai and eight (9.2%) as Leptotrombidium scutellare
Summary
Known as tsutsugamushi disease, is a mite-borne infectious disease that is endemic in a triangular geographic region containing the Indian subcontinent, northern Australia and the Far East. If a disease flows into a densely populated urban area and attains its endemicity, it will have a significant impact in terms of a disease burden and differential diagnosis in clinical practices. Urban scrub typhus cases that were suspected to occur within Seoul, the largest city in South Korea, have been frequently noted in clinical practices. Seoul is the capital city of South Korea which is located in the northwestern region. Our study was conducted to investigate the status of indigenous urban scrub typhus and its clinical characteristics in Seoul at more northern latitude. Scrub typhus is an endemic disease in Asia It has been a rural disease, but indigenous urban cases have been observed in Seoul, South Korea. Urban scrub typhus may have a significant impact because of the large population
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