Molecular characterisation of the hepatitis A virus circulating in the 2001-2005 outbreaks in Thailand.

In a recent study of hepatitis A virus (HAV) in Thailand, viral isolates recovered during several outbreaks of infection that occurred between 2001 and 2005 were genotyped and subjected to phylogenetic analysis. Anti-HAV IgM was detected, by ELISA, in many of the 283 serum samples that were collected from the provinces of Suphanburi, Songkhla, Chiangrai and Lampang: 40 (48.2% of those investigated), 38 (47.5%), 25 (41.0%) and 32 (54.2%), respectively. The HAV RNA in the positive samples was reverse transcribed and amplified, using a nested PCR focussed on the VP1-2A region, before the nucleotides of the VP1-2A region of each HAV-RNA-positive sample were sequenced. All the isolates investigated clustered in subgenotype IA and, hence, are closely related to the strains previously investigated in Thailand. When the genome of one sample from an outbreak in Lampang (LP014) was fully sequenced, the results of genome comparison and phylogenetic analysis again indicated subgenotype 1A, which appears to be the predominant form of HAV circulating throughout Thailand.