A case of scrub typhus presumably infectd in Ohita Prefecture, Kyushu was experienced by the authors in October 1961 with successful isolation of Rickettsia orientalis. The patient was a twenty four years old male, a member of the Ground Self Defence Force. He was engaged in a field exercise at Kijima Plateau in Ohita prefecture from October 10 to October 17. After he returned to Yamaguchi City, he noticed fever, 39°C on Ochtober 22. Since then he was suffering from high fever every afternoon until his sdmission into the Yamaguchi Red Cross Hospital on October 31, 1961.
On admission his temperature was 39.5°C. Marked macular rash on his face, trunk and extremities and enlargement of generalized lymph nodes and of spleen were noted. There was an eschar covered by a black scab at 10 cm above right malleolus medialis. On the 16th day of the illness agglutinin titer for OX-K strain of B. proteus rose to 1: 320.
On the 10 th day of the illness his venous blood was injected intraperitoneally into three mice to isolate the causative agent. The injected mice began to die from 14 days after inoculation. At necropsy they showed viscous peritoneal fluid and enlarged spleen. Microscopic examination of impression smears made from the peritoneal fluid and stained by Giemsa's method revealed numerous rickettsiae in protoplasm of cells.
Immunologically this strain was identified as R. orientalis by cross-immunity tests performed in mice.
Scrub typhus had been long believed to occur only in Niigata, Yamagata and Akita Prefecture unti 1946, when it was found at the foot of Mt. Fuji. Since then many cases of scrub typhus have been reported from various areas of Japan. In kyushu, however, though the authors and some other investigators found R. orientalis from field mice, any undoubted human case has never been reported.
The first case of scrub typhus confirmed by recovering R. orientalis from the blood of the patient was reported in this paper.

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