[Tsutsugamushi disease found in Haruna District, Gunma Prefecture--evaluations of the clinical features and the outbreak pattern].

From November to December in 1990, 7 cases of tsutsugamushi disease were found first in the southern foot of Mt. Haruna of Gunma Pref., Japan. The present study was conducted to clarify the clinical features and the outbreak pattern of rickettsial infection in this area. All the patients consisting of 6 males and 1 female farmers were admitted to our hospital, complaining of high fever, chills and skin rash on 5-12 days after working in the field. Based on laboratory examinations and one (or two) typical eschar, a tentative diagnosis of tsutsugamushi disease was made and all patients became better soon after the therapy with intravenous administration of minocyclin (200 mg/day). The high titer of serum antibody to Karp type Rickettsia (Orientia?) tsustugamushi was detected by an immunoperoxidase test (IP) in most of the patients, and also a Karp-like strain was isolated from only one patient, probably due to low virulence to mice. The agricultural areas along the Agatuma and Nakuta rivers in the northern foot of Mt. Haruna have been well known as the most endemic foci of the disease in Gunma Pref. Nevertheless, it was suggested that outbreaks of the disease might be potentially wide-spread throughout this Pref., when the prevalences of the disease were evaluated as incidences to a hundred thousand inhabitants or adjusted by the density of agricultural populations of each administrative divisions. As most of the patients in Gunma Pref. have been officially reported in autumn, a statistical trial indicates that there is a significant correlation between the levels of temperature and outbreaks of the disease in autumn.(ABSTRACT TRUNCATED AT 250 WORDS)