Seroepidemiology of hepatitis E virus in Hong Kong

Abstract

Hepatitis E is a disease caused by infection with the hepatitis E virus (HEV), which was first identified in 1978. HEV is a single-strand, positive-sense RNA virus with a 7.2-kilobase viral genome. According to statistics from WHO, an estimated 20 million new hepatitis E infections occur worldwide each year, leading to approximately 3.4 million symptomatic cases and 70,000 deaths. The primary transmission route varies between developing and developed areas. In developing regions, the main route is fecal-oral spread, while in developed regions, the predominant route is foodborne transmission through undercooked pork products. It should be noted that rat hepatitis E, a divergent variant which is zoonotic from rats, is causing an increasing number of human cases worldwide. bHEV is a major variant circulating worldwide among humans, pigs and wild boars. Rat HEV shares only 50-60% genomic identity with bHEV, and their antigens are quite distinct. Most commercial kits, such as the Wantai HEV ELISA kit, cannot differentiate between bHEV and rHEV. The seroprevalence of rHEV has not been thoroughly explored. HEV can cause acute hepatitis, and while most cases within the general population are self-limiting or even asymptomatic, chronic infection can develop in immunocompromised individuals. Chronic infection is defined as hepatitis E viremia persisting for at least three months and can lead to liver fibrosis and cirrhosis if left untreated. Most reported chronic HEV infections in immunocompromised individuals occur in solid organ transplant (SOT) recipients. It remains unclear whether immunocompromised individuals are more susceptible to HEV infection than the general population. In this study, commercial HEV enzymatic immunoassay, in-house bHEV and rHEV parallel enzyme immunoassays, and HEV quantitative reverse transcription polymerase chain reaction (RT-qPCR) were utilized to investigate HEV seroprevalence, differentiate seroprevalences between bHEV and rHEV, and determine HEV RNA molecular prevalence, respectively. Additionally, HEV infection rates between immunocompromised patients and age-matched individuals with competent immune systems were compared. In summary, it was discovered that overall hepatitis E seroprevalence is higher in SOT recipients compared to the general population. At least 26 active or recent HEV infections were identified. Continuous reinforcement of dietary precautions is needed for SOT recipients. Moreover, a low-level endemic presence of rHEV in Hong Kong, with a seroprevalence of approximately 0.5%, was discovered, and increasing age was found to be a risk factor for both bHEV and rHEV. Low-level food contamination due to rodent infestation is speculated to be the most likely source.