Characterization of hepatitis E virus from outbreak and sporadic cases in Turkmenistan

Large outbreaks and sporadic cases of hepatitis E have been reported in Central Asia. We assessed the genetic relatedness of hepatitis E virus (HEV) strains from outbreak and sporadic cases in Turkmenistan. Specimens from outbreak and sporadic cases of acute hepatitis non-A, non-B were tested by reverse transcription (RT)polymerase chain reaction (PCR) to identify the presence of HEV RNA; nucleotide sequences were analyzed. HEV RNA was detected from 23/ 156 (15%) outbreak cases and 2/23 (9%) sporadic cases. The HEV outbreak isolates represented 14 unique sequences with genetic distances varying between 0.3% and 8.6%,12 of which were closely related, with distances between 0.3% and 5.6%. Two unique sequences from outbreak cases 32 and 42 were closely related (99.7%) and shared 91.8-93.4% of sequence with the other 12 strains. The two strains were closely related to the previously published isolates from Burma (99.7-100%) and India-Madras (95.7-96. 1%). The two 1994 sporadic HEV strains were 97.4% distinct, wile revealing 91.4-94.1% homology to 1985 strains, and 94.4-94.7% to HEV from the neighboring China and Pakistan. Genetic diversity of HEV that caused the hepatitis E outbreak in Turkmenistan in 1985 suggests heterogeneity of viral sources. Sporadic hepatitis E that occurred in 1994 was caused by viral strains genetically distinct from those causing the outbreak in 1985, yet closely related to HEV from neighboring countries. The study suggests that circulation of a broad variety of strains of HEV may occur in Central Asia, regardless of international borders, presenting a significant public health threat to the population of the region.