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

Objective: This study aimed to describe the epidemiological and clinical characteristics of endemics of two rickettsial diseases, scrub typhus (ST) and Japanese spotted fever (JSF), in Japan. Methods: We conducted a retrospective, descriptive epidemiological assessment of cases notified via national surveillance from 2007?2016. Results: Over the 10-year period, 4185 ST and 1765 JSF cases were notified; of these, 20 (0.48%) cases of ST and 16 (0.91%) cases of JSF were fatal at the time of reporting. The elderly had higher notification rates and fatalities. While the annual number of ST notifications was stable and cases were reported from a broad geographic range, the number of JSF reports increased three-fold, expanding from the southwest to the east. The seasonality of ST varied by region and was more common during spring/summer in the north and autumn/winter in the south; 78% of cases occurred during autumn/winter, mainly in the southern region. Most of the fatal ST cases occurred in the spring/summer and occurred in the northern region. Conclusion: Our analysis identified seasonal and regional variations in the distribution of rickettsiosis. These variations were most likely to be related to the ecology of the vectors and etiological agents. Knowing the recent epidemiological and clinical features of ST and JSF can support clinical diagnosis and guide preventative activities against these vector-borne diseases. ? 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-ncnd/4.0/).

Automated summary

This study aimed to describe the epidemiological and clinical characteristics of scrub typhus and Japanese spotted fever in Japan over a 10-year period. The study found that the elderly had higher notification rates and fatalities, with stable notifications for scrub typhus and an increase for Japanese spotted fever expanding towards the east. Seasonality and regional variations in the distribution of the diseases were identified, likely related to the ecology of vectors and etiological agents, providing valuable information for clinical diagnosis and preventative activities.