Evaluation of National Tsutsugamushi disease surveillance-Japan, 2000

In Japan, Tsutsugamushi disease, which is caused by Orientia tsutsugamushi, is re-emerging with newly recognized strains and is now endemic in all prefectures except Hokkaido and Okinawa. We analyzed recent surveillance data to describe the epidemiology of Tsutsugamushi disease and to evaluate the newly implemented national surveillance system according to the CDC guidelines for evaluating surveillance systems. In 2000, 756 cases of Tsutsugamushi disease were reported from 37 of 47 prefectures; two of these cases were fatal. The median age of case-patients was 64 years (range: 2-94 years); 414 (54.8%) were male. In northern Japan, most cases were diagnosed in the months of May through July and in the months of October through December, and in southern Japan, cases were diagnosed almost year-round with a peak from October through December and in January. Reporting and transfer of surveillance information from the prefecture to the national level was effective and timely, but the completeness and quality of case reporting could still be improved. The current system for Tsutsugamushi disease surveillance is useful for describing epidemiologic patterns by time, prefecture, and demographic characteristics. However, collection of additional information on suspected place of transmission, activity performed at the place of transmission, or the case-patient's profession would likely make the system more valuable for outbreak detection and for better defining populations at risk.