**Author details**

such as higher possessing JE virus antibody in pigs or mosquitoes led to an increase in the

On the other hand, acute encephalitis/encephalopathy in children under 15 years of age has occurred in approximately 1,000 cases per year, as indicated in a large-scale survey of Japan. The etiology in order from most prevalent to least prevalent is influenza (25%), HHV-6 (11%), and rotavirus (4%) (Morishima, 2009). The incidence of HHV-6 encephalopathy, 7.0 per 100,000 infants, was estimated from the infant population of Japan, and severe neurolog‐

Regarding the onset age of the 14 HSE patients, the under-30-year-old cases included one infant, a 14-year-old boy, and a 24-year-old man; the mean age of all 14 patients was 47.3 years. The peak onset age was in the 60s, although our past study identified two peaks at 20 and the 50s. The oldest HSE patient, an 88-year-old man, died of complicated pneumonia one month after admission, and another 80-year-old man suffered from severe memory im‐ pairment as a sequela, despite early acyclovir treatment. The upward trend of elderly pa‐ tients with HSE may reflect the 'graving' of the Japanese populations, and also suggests that the reactivation of HSV can occur even in elderly people (Suzuki et al, 2012). All four of present patients with VZV-associated encephalitis had favorable outcomes after high-dose

All four of the JE patients we identified were elderly (including a 93-year-old), and their im‐ munity to the JE virus was probably decreased or absent (Ayukawa et al 2002, Lee et al 2012). Presently, there is no specific therapy for JE, and thus JE vaccination might be advisa‐

The incidence of FluE has increased in Japan since the 1997 winter influenza season. FluE affects mainly children under 10 years old (Okumura et al, 2012, Watanabe et al, 2012). In our hospital, 10 adult FluE cases were recognized in the 2002―2012 examination period, in‐ cluding four patients over 15 years old who were part of the epidemic of the new pig influ‐ enza variant in 2009 (Umemura et al, Lee N et al, 2010). For the pediatric patients, steroid pulse, intravenous immunoglobulin or low-temperature therapies were performed. The adult patients had favorable outcomes except for one case of Reye syndrome. Although hy‐ percytokinemia has been contended to contribute to the pathogenesis, the IL-6 levels in our

We analyzed the cases of 105 patients with acute viral encephalitis/encephalopathy who were treated at our emergency center, St. Mary's Hospital, Kurume City during the 10 years from 2002 to 2011. Fourteen HSE cases, 4 of herpes zoster-related encephalitis, 1 of HHV-6 white matter encephalopathy, 4 of JE, 20 of FluE, 3 of mumps encephalitis, and 1 of rotavirus encephalopathy were identified. As other types, 12 cases of viral-related ADEM and 7 cases of non-herpetic limbic encephalitis including anti-NMDAR encephalitis/encephalopathy were observed. The etiology of the remaining 42 cases of viral encephalitis was unknown.

ical complications remained in half of these infants (Ohashi, et al, 2006).

number of occurrences of JE.

50 Encephalitis

of intravenous acyclovir therapy.

ble for elderly people in the epidemic area.

adult cases were in the normal range.

**5. Conclusion**

Hiroshi Shoji1 , Masaki Tachibana2 , Tomonaga Matsushita2 , Yoshihisa Fukushima2 and Shimpei Sakanishi3

