Neurological assessment of Japanese encephalitis survivors at hospital discharge does not predict long-term outcome. Seizures and shock are treatable risk factors for a poor outcome at hospital discharge and at long-term follow-up visits.

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SummaryJapanese encephalitis virus (JEV) is an important encephalitis virus in Asia, but there are few data on Malaysia. A hospital-based surveillance system for Japanese encephalitis (JE) has been in operation in Sarawak, Malaysia, for the last 10 years. JEV is endemic in Sarawak, with cases occurring throughout the year and a seasonal peak in the last quarter (one-way anova, P < 0.0001). Ninety-two per cent of 133 cases were children aged 12 years or younger; the introduction of JE vaccination in July 2001 reduced the number of JE cases (84 in the four seasons prior to vs. 49 in the six seasons after, McNemar's test, P = 0.0001). After implementation of the programme, the mean age of infected children increased from 6.3 to 8.0 years (Student's t-test, P = 0.0037), suggesting the need for a catch-up programme. (Fang et al. 1980) and Penang in 1988(Cardosa et al. 1995. A series of studies from the 1960s documented JEV isolation from mosquitoes in Sarawak and showed that pigs play an important role as amplifying hosts (Bendell 1970;Simpson et al. , 1974Simpson et al. , 1976Bowen et al. 1975). Seroconversion to JEV in pigs suggested that transmission occurs throughout the year with infection rates higher in the period from November to January coinciding with the major seasonal population increase of Culex tritaeniorynchus (Simpson et al. 1976).In 1997, a pilot hospital-based surveillance study for JE was set up in Sibu Hospital in Sarawak, followed in 1998 by passive surveillance for all other hospitals in the state. Patients were suspected to have Japanese encephalitis if they had fever (or a history of fever), and at least one of the following: reduced level of consciousness (lethargy, drowsiness or coma); severe headache; neck stiffness; tense anterior fontanelle; focal neurological signs and prolonged seizures.Paired sera and paired CSF for each patient were considered to be the ideal specimen set. However, in reality the complete specimen set was not obtained from many cases. Specimens were tested for JEV specific IgM by MAC ELISA (Venture Technologies Sdn Bhd, Malaysia), which distinguishes IgM elicited by JEV from that elicited by dengue viruses (Solomon et al. 1998;Cardosa et al. 2002). The sensitivity, specificity, positive predictive value and negative predictive value of the test used were 83%, 99%, 0.98 and 0.92, respectively for CSF and 91%, 95%, 0.92 and 0.94, respectively for serum. All cases of encephalitis with specific IgM to JEV in serum and ⁄ or CSF were considered to have been infected recently with JEV. It should be noted that patients with single IgM-negative sera or CSF cannot be considered conclusively negative because an IgM seroconversion can occur in a second specimen. With only single specimens, we lose this information. Here we report data obtained over a 10-year period from 1997 to 2006. Four seasons into the study period, in July 2001 the Sarawak Health Department implemented a JE vaccination programme. JE vaccine (Biken, Japan) was included in the Expanded Programme of Immunizati...