Transmission of hepatitis E virus in Bangladesh: A phylogenetic analysis of viral sequences from a nation-wide hospital-based acute jaundice surveillance program, 2014-2017

BackgroundHepatitis E virus (HEV) genotype 1 is a major cause of acute jaundice in Bangladesh, yet the transmission dynamics and genetic diversity of this virus remains inadequately characterized. This study aims to elucidate the genetic landscape and transmission patterns of HEV infection in Bangladesh through phylogenetic analysis of viral sequences obtained from a nation-wide surveillance program. Methodology/Principal FindingsWe analyzed 104 partial HEV open reading frame 1 (ORF-1) sequences collected from acute jaundice patients admitted to six tertiary hospitals across Bangladesh during December 2014- September 2017. Phylogenetic trees were constructed using maximum likelihood methods, and Bayesian clustering was employed to assess genetic diversity and transmission patterns. All sequences were identified as HEV genotype 1 (HEV-1), with 10 sequences predominantly collected in 2017 classified as subtype 1g, forming a distinct cluster. A lack of geographic clustering across the sequences suggests widespread transmission across the country rather than geographically distinct transmission networks. Of the 104 sequenced cases, 5 (5%) were associated with fatal outcomes, although these sequences did not cluster phylogenetically. Conclusions/SignificanceThis phylogenetic analysis provides evidence of widespread transmission of HEV-1 across Bangladesh, with a reduction in genetic diversity in 2017 suggesting the potential emergence of a dominant viral cluster around that time. Given the paucity of clinical surveillance of HEV, genomics may provide new insights into unobserved aspects of the transmission of the virus locally and globally. Author summaryHepatitis E virus genotype 1 (HEV-1) is a major cause of acute jaundice in Bangladesh, but many cases go unreported, and the viruss transmission patterns are not well understood. In the absence of reliable clinical surveillance data, analyzing the genetic diversity amongst viral samples isolated from infected people can help us infer transmission patterns. To better understand how HEV-1 circulates in Bangladesh we studied 104 HEV-1 genetic sequences isolated from acute jaundice patients at 6 hospitals across the country between 2014-17 and inferred how the sequences most likely relate to each other based on their genetic similarities. We found that the viral sequences did not cluster by region in which the patient lived but rather genetically similar viruses were isolated in geographically distant regions suggesting widespread transmission across the country. Our results captured a reduction in genetic diversity in 2017 with many sequences isolated that year forming a distinct genetically similar group suggesting a potential shift in the viral population or a significant outbreak event around that time. Given the scarcity of clinical surveillance of HEV-1, such insights into unobserved aspects of transmission have the potential to improve our understanding of HEV-1 epidemiology.