Abstract
Gampaha Deputy Provincial Director of Health Services division reported a large number of Japanese encephalitis cases during 1996 to 1997. Notified cases included unconfirmed and confirmed cases. A study to determine the true disease burden was considered necessary. Proportion of undifferentiated fever cases due to Japanese encephalitis virus varies in different populations and the Sri Lankan situation is not known. The objectives were to determine the proportion of undifferentiated fever cases and encephalitis cases due to Japanese encephalitis virus; and the case fatality rate and frequency of neurological sequelae in Japanese encephalitis, in a tertiary care hospital in Gampaha. A cross-sectional descriptive study was carried out in the paediatric and medicine units of the North Colombo Teaching Hospital, Ragama during 1998 to 2000. Ninety three randomly selected patients with a diagnosis of undifferentiated fever from whom paired sera could be collected and 32 patients suspected of encephalitis, which were not overtly due to mumps, measles or chicken-pox were included. The Armed Forces Research Institute in Medical Sciences Enzyme linked immunosorbent assay for anti-Japanese encephalitis virus immunoglobulin M and G was used to confirm Japanese encephalitis virus infection. One of 93 (1.08%) undifferentiated fever cases was due to Japanese encephalitis virus infection. Eleven of 32 (34.38%) encephalitis cases had Japanese encephalitis virus infection and 3 (27.3%) had IgM antibodies to Japanese encephalitis virus in cerebrospinal fluid. Case fatality rate and sequelae at discharge were 11.1% each. Japanese encephalitis virus was an important cause of encephalitis in Gampaha during this period. DOI: http://dx.doi.org/10.4038/sljid.v2i1.3321 Sri Lankan Journal of Infectious Diseases Vol.2(1) 2012: 19-27
Highlights
The Japanese encephalitis virus (JEV) was first isolated in Sri Lanka by Hermon and Anandarajah in 1968 from the serum of a child admitted to hospital in a comatose state.1Serological surveys done in various parts of the island in 1976 and 1977 identified certain regions as endemic for JEV infections
One of 93 (1.08%) undifferentiated fever cases was due to JEV infection as diagnosed by the enzyme immunoassay (EIA)
In a study carried out in Penang, Malaysia, among paediatric patients with non-specific febrile illness, 0.4% (2/482) were due to JEV infection during 1990 to 1992.12In another study conducted in 1967 in South Vietnam among American servicemen presenting with acute pyrexia of unknown origin, 6.8% (54/793) of cases were attributed to JEV.[13]
Summary
The Japanese encephalitis virus (JEV) was first isolated in Sri Lanka by Hermon and Anandarajah in 1968 from the serum of a child admitted to hospital in a comatose state.1Serological surveys done in various parts of the island in 1976 and 1977 identified certain regions as endemic for JEV infections. Based on data obtained from the Annual Health Bulletin, The Gampaha Deputy Provincial Director of Health Services (DPDHS) division was one of the divisions reporting a relatively large number of JEV cases during 19963 – 1997.4 Except for a seroprevalence study in the Ragama area in 19885, there are no recent published studies carried out in the Gampaha District for JEV infections. The number of viral encephalitis cases notified to the Sri Lanka Epidemiology Unit include both laboratory confirmed and unconfirmed cases. A study to determine the true disease burden of JEV infection based on laboratory confirmed results was considered necessary. As reviewed by Vaughn and Hoke the ratio of apparent to inapparent infection may be different in different populations, andbetween 50 and 300 infections occur for each clinical case of encephalitis that is identified.6Monath has estimated a more critical ratio of 200:1 to 300:1.7
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