Jpn. J. Infect. Dis., 57, 63-66, 2004

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Short Communication

An Unexpected Outbreak of Japanese Encephalitis in the Chugoku District of Japan, 2002

Ryusuke Ayukawa, Hiroshi Fujimoto, Mitsuyoshi Ayabe, Hiroshi Shoji*, Ryukichi Matsui¹, Yuko Iwata², Hitoshi Fukuda², Kazuhide Ochi³, Koichi Noda³, Yoichi Ono⁴, Kenichi Sakai⁴, Yasushi Takehisa⁵ and Kotaro Yasui⁶

The First Department (Neurology) of Internal Medicine, Kurume University School of Medicine, Fukuoka 830-0011, ¹Department of Internal Medicine, Tsuwanokyouzon Hospital, Shimane 699-5604, ²Department of Neurology, Masuda Red Cross Hospital, Shimane 698-0003, ³Department of Neurology, Hiroshima National Hospital, Hiroshima 739-0041, ⁴Department of Neurology, National Okayama Medical Center, Okayama 701-1192, ⁵Department of Neurology, Tottori Municipal Hospital, Tottori 680-8501 and ⁶Department of Microbiology, Tokyo Metropolitan Institute for Neurosciences, Tokyo 183-8526, Japan

(Received December 12, 2003. Accepted March 8, 2004)

*Corresponding author: Mailing address: The First Department (Neurology) of Internal Medicine, Kurume University School of Medicine, Asahimachi 67, Kurume, Fukuoka 830-0011, Japan. Tel: +81-942-35-3311, Fax: +81-942-31-7703, E-mail: hshoji@med.kurume-u.ac.jp

SUMMARY: Six patients unexpectedly presented with Japanese encephalitis (JE) from early August to mid-September 2002 in the Chugoku district of Japan. The mean age was 67.5 years (range 42 - 89 years); the onset period in two patients shifted to the middle of September. The JE virus was isolated from the cerebrospinal fluid samples from two patients, and the strain isolated in the one was identified as genotype III. Neurologically, consciousness impairment, meningeal signs, rigidity, hemiparesis, tetraparesis, and convulsive seizures were commonly observed. Magnetic resonance imaging uniformly revealed high signal intensities in the bilateral thalami, brainstem (substantia nigra), hippocampi, and brain cortices. In all patients, acyclovir was used, due to the unexpected outbreak of JE. Five patients, except for one without sequelae, had a severe outcome, including one death. This report indicates that JE in Japan is still a threat to adults and the elderly with decreased or absent immunity to the JE virus.

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