S-46. Investigations of Hepatitis A outbreak from Shimla

An outbreak of viral hepatitis from Shimala, Himachal pradesh was investigated during January-February 2007. Approximately 450 cases were reported from Kusumpti, Vikas Nagar, Panthaghati, Mehi and New Shimla locality having a population of around 50,000 (attack rate ∼ 1%) This area receives water from Ashwani Khud water supply system. Since one year, 4 kilometers upstream of Ashwani Khud water supply system treated sewage water from Malayana sewage treatment plant was let into the stream. 87 blood samples with relevant case history, five liters each affluent and effluent sewage samples from Malayana sewage treatment plant, 5 liters water from collection point of Ashwani Khud water supply system, 20 liters treated water from Ashwani Khud water supply system and 20 liters water from Kusumpti storage tank were collected. All the serum samples were screened for anti HAV IgM, anti HAV IgG, anti HEV IgM and anti HEV IgG. Acute-phase eight serum samples, sewage samples and concentrated water samples were processed for detection of HAV RNA by nested RT-PCR. Primers representing the conserved 5’ non-coding region (5’NC) were used. In addition nearly entire genome (excluding extreme 5’ end) was amplified from one of the above serum sample using different sets of primer covering entire genome. Of the 87 serum samples 55 (71.4%) were positive for HAV IgM. HAV RNA was detected in all 8 serum samples, sewage samples and water samples from Ashwani Khud water supply system. Phylogenetic analysis based on nearly complete genomic sequence, complete ORF sequence and 5’non-coding region sequence showed hepatitis A virus of genotype IIIA. Thus the etiological agent of the present outbreak was found to be Hepatitis A virus, genotype IIIA.