Descriptive epidemiology of rickettsial infections in Japan: Scrub typhus and Japanese spotted fever, 2007-2016.

Abstract Objective This study aimed to describe the epidemiologic and clinical characteristics of Scrub typhus (ST) and Japanese spotted fever (JSF), rickettsial diseases endemic in Japan. Methods We conducted a retrospective, descriptive epidemiologic assessment of cases notified through national surveillance from 2007-2016. Results Over the 10-year period, 4,185 ST and 1,765 JSF cases were notified, and 20 (0.48%) ST and 16 (0.91%) JSF cases were fatal at the time of report. The elderly had higher notification rates, along with fatalities. For ST, while the annual number of notifications was stable and cases were reported from a broad geographic range, JSF reports increased three-fold, expanding from the southwest to the east. Seasonality of ST varied by region, being more common during spring–summer in the north and autumn–winter in the south; while 78% occurred during autumn–winter, mainly in the southern region, most fatal ST occurred in the spring–summer, and were from the northern region. Conclusion Seasonal and regional variations in the distribution of rickettsiosis was observed, likely related to the ecology of the vectors and etiologic agents. Knowing the recent epidemiological and clinical features of ST and JSF can support clinical diagnosis and guide prevention against these vector-borne diseases.