Epidemiological study of acute encephalitis in Tottori Prefecture, Japan.
OBJECTIVE
To conduct an epidemiological survey of acute encephalitis focusing on non-herpetic acute limbic encephalitis (NHALE) in Tottori Prefecture, western area of Japan.


METHODS
A questionnaire survey on the annual number of patients aged 16 years or more with acute encephalitis from 2001 to 2005 was undertaken in 2006.


RESULTS
During the study period, 49 patients were diagnosed with acute encephalitis. The subtype of acute encephalitis was as follows: 10 patients with herpes simplex encephalitis (HSE), 12 patients with NHALE, 4 patients with paraneoplastic encephalitis, 2 patients with encephalitis associated with collagen disease, one patient with viral encephalitis other than HSE, 20 patients with encephalitis with unknown causes. The service-based incidence rate of acute encephalitis was 19.0 per million person-years. The incidence rate of NHALE subtype was 4.7 per million person-years.


CONCLUSIONS
Our epidemiological survey indicated an estimated 550 patients would develop NHALE per year in Japan, suggesting that NHALE may not be a rare disorder.
Wada-Isoe
K
K
Department of Neurology, Faculty of Medicine, Institute of Neurological Sciences, Tottori University, Tottori, Japan. kewada@med.tottori-u.ac.jp
Kusumi
M
M
Kai
T
T
Awaki
E
E
Shimoda
M
M
Yano
H
H
Suzuki
K
K
Nakayasu
H
H
Oota
K
K
Kowa
H
H
Nakashima
K
K
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003095:Collagen Diseases / Q000150:complications; D004660:Encephalitis / Q000145:classification / Q000453:epidemiology* / Q000209:etiology; D018792:Encephalitis, Viral / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D020363:Limbic Encephalitis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012189:Retrospective Studies; D012424:Rural Population; D011795:Surveys and Questionnaires