This topic was previously touched on 2 years ago. The speculation at that time was whether hepatitis E in Singapore is also linked to the consumption of undercooked pork. This seems to be answered by a new study (behind a pay wall) that has just been published in the journal Zoonoses Public Health by investigators from the microbiology blogger‘s department, the Environmental Health Institute of the National Environment Agency, Singapore Food Agency, and Duke-NUS.

As reported in the paper, positive HEV IgM (2012 to 2016) and IgG (2007 to 2016) results were retrieved from the Singapore General Hospital Virology Laboratory to construct the sero-epidemiology of hepatitis E in Singapore. This is possible because that laboratory is the primary testing site for HEV serology in Singapore. In addition, a total of 449 residual human sera samples that were positive for HEV IgM were randomly selected for HEV genotyping, but unfortunately only 36 pork livers bought from wet markets and supermarkets were tested for HEV (of which only 3 were positive).

The results are interesting. Firstly, the incidence of acute HEV has risen among the Singapore resident (i.e. citizens and permanent residents) population, but fallen among the non-resident population. The majority of residents infected were of Chinese ethnicity.

The majority (93%) of HEV infecting the Singapore residents belonged to Genotype 3, whereas Genotype 1 comprised the majority of HEV infecting the non-resident cases. The 3 HEV strains obtained from pork liver sold locally also belonged to Genotype 3, and upon phylogenetic analysis of sequenced amplicons, were between 94.5% and 98.5% identical to the local human Genotype 3 strains that had been sequenced. The attached figure from the paper is not easy to get one’s head around, but the white circles indicate human HEV strains from the current study, while the 3 black circles indicate pork HEV strains from the current study. Black triangles indicate human HEV strains from previous local studies that have been sequenced.

What the results seem to suggest – other than Genotype 3 being the predominant HEV genotype in Singapore – is that hepatitis E cases in Singapore could be associated with consumption of pork products, especially given that the vast majority of Singapore residents infected were of Chinese ethnicity. Supplementary Table 3 was also interesting for the long list of (20) countries from which Singapore imports pork.