Journal of Clinical Virology 31 (2004) 153–159 Japanese encephalitis virus (JEV) is an important cause of encephalitis among children in Cuddalore district, Tamil Nadu, India Lalitha Kabilan a,∗ , Sudhansu Vrati b , S. Ramesh d,1 , S. Srinivasan c,2 , Mohan Babu Appaiahgari b , N. Arunachalam a , V. Thenmozhi a , S. Muthu Kumaravel a , P. Philip Samuel a , R. Rajendran a a Centre for Research in Medical Entomology (Indian Council of Medical Research), 4 Sarojini Street, Chinna Chokkikulam, Madurai-625002, India b Department of Virology, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India c Department of Paediatrics, Jawaharlal Institute of Post graduate Medical Education and Research, Dhanvantri Nagar, Pondicherry-605006, India d Department of Pediatrics, Rajah Muthiah Medical College and Hospital, Annamalai University, Annamalai Nagar-608002, Chidambram, India Received in revised form 17 January 2004; accepted 8 March 2004 Abstract Background: Japanese encephalitis (JE) is endemic in Cuddalore district, Tamil Nadu (TN), Southern India. The reports of JE cases from the local hospitals did not reflect the actual disease burden. It is likely that these cases were attending the nearby referral hospitals, for want of better treatment facilities. Objectives: Between July 2002 and February 2003, a pilot study was undertaken to examine whether JE was a component of paediatric acute encephalitis syndrome (AES) reported to two major referral hospitals adjacent to Cuddalore, and to map the distribution of the JE cases. Study design: A total of 58 hospitalized children [0–15 years] with AES were investigated. Other than the routine laboratory investigations, either CSF or sera or both [depending on the availability] collected from these children were analyzed at Center for Research in Medical Entomology, Madurai (TN) for JEV-antigen, antibody detection, virus isolation and virus genome detection by indirect immunofluorescence, MAC enzyme linked immunosorbent assay (ELISA), insect bioassay and by reverse transcriptase polymerase chain reaction (RT-PCR), respectively. Results: JE was established in 17 (29%) of 58 AES cases; half of the AES cases [31/58, 53%] and 59% [10/17] of JE cases were confined to JE-endemic areas in Cuddalore district. The JE confirmation scored by different assays varied according to the clinical phase of the illness. The attack rate was high among the children aged 3–8 years. The monthly distribution of acute encephalitic syndrome cases followed the distribution of JE cases [coinciding with the rainy season in this region] suggesting encephalitis of JE origin. Conclusion: In JE-endemic areas, the actual JE burden can be estimated by the collection of JE case reports from the local hospitals and from the referral hospitals. Building of diagnostic facilities in hospitals for JE is necessary to achieve this goal. © 2004 Elsevier B.V. All rights reserved. Keywords: Acute encephalitis syndrome; Hospitalized children; Japanese encephalitis; Southern India 1. Introduction Japanese encephalitis (JE) a mosquito-borne viral disease is a serious public health problem in Asia ( Libraty et al., 2002). JE is endemic in few states of India ( Namachivayam and Umayal, 1982;Reuben and Gajanana, 1997; Sarkari ∗ Corresponding author. Tel.:+91-452-2651820/2650281; fax: +91-452-2530660. E-mailaddresses: lalithakabilan@sify.com, d1crme@sify.com (L. Kabilan), doctorramesh@eth.net (S. Ramesh), srinivasan @yahoo.co.uk (S. Srinivasan). 1 Tel.:91-414-4238010. 2 Tel:91-413-274008. et al., 1984). JE is highly endemic in few districts of Tamil Nadu (TN), Southern India (Ravi et al., 1989; Reuben and Gajanana, 1997).The poorJE surveillance system could not projecthe actual dimension of the disease problem in these areas. The probability of a child receiving an in- fective (JEV)mosquito bite during the JEV transmission season [September to December] in JE-endemic villages of Cuddalore district, TN was reported to be between 0.50 and 0.75. The passive surveillance of collection of JE case reports from the local health centers of these villages did not correlate with the JEV transmission parameters. It was understood that mostof the acute encephalitis syndrome cases (AES; patients with encephalitis and related central nervous system disorders) were attending the two nearby 1386-6532/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jcv.2004.03.011