Human and Porcine Hepatitis E Viruses, Southeastern Bolivia

References 1. Infectious Disease Surveillance Center. Virus isolation/detection from hand, foot and mouth disease cases, 2007–2011. Hand-foot-mouth disease cases reported per sentinel weekly [cited 2011 Nov 7]. of the VP1, VP2, and VP4 regions for molecular typing of human enteroviruses. nail matrix arrest following hand-foot-mouth disease [in Japanese]. To the Editor: Hepatitis E virus (HEV) genotypes 3 and 4 are considered to be primarily zoonotic (1). However, recent data indicate that both genotypes can be transmitted among humans through other routes (2,3). Observations of genetic distinctiveness between swine and human HEV strains circulating within the same region argue against exclusivity of zoonotic transmission (4). A recent report presented a remarkable example of such distinction between genotype 3 isolates in rural communities in southeastern Bolivia (5). We examined HEV sequences obtained in that study to show the independent genetic origin of swine and human variants. Findings suggest disjunction between human and swine HEV strains in this epidemiologic setting, despite the potential for extensive cross-species exposure. Using reference sequences from Lu et al. (6), we conducted subtype analysis of HEV open reading frame 2 sequences at nucleotide positions 826–1173 (GenBank accession no. AF060668) from isolates from 2 rural communities in southeastern Bolivia (5). Analysis showed that swine sequences belonged to subtype 3i and that the human sequences belonged to 3e. We collected all available GenBank genotype 3 sequences covering this genomic region for which the dates of collection were documented. Sequences were used to estimate the time from the most recent common ancestor (tMRCA) by using BEAST version 1.6.1 (7). Estimated tMRCA for GenBank sequences was longer than for sequences from Bolivia alone (Table) or for all genotype 3 sequences together (Table). To reduce the effect of close relatedness among human or swine HEV sequences from Bolivia on the tMRCA estimate, we used only 1 representative sequence per species from each community in the fi nal analysis. This analysis identifi ed an estimated tMRCA similar to that seen for GenBank sequences alone (Table, model F vs. model D). This estimate indicates that human and swine HEV isolates from southeastern Bolivia last shared a common ancestor ≈275 years ago (Table, model F). Thus, swine HEV strains from both rural communities belonged to subtype 3i, and the human HEV strains identifi ed from the community of Bartolo, Bolivia, belonged to subtype 3e and shared an ancestor with swine strains almost 3 centuries ago. This …