Epidemiology and clinical characteristics of rat hepatitis E virus infection in humans

Rocahepevirus ratti genotype 1 (rHEV), commonly known as rat hepatitis E virus, is a recently identified cause of viral hepatitis. We compared rHEV infections with conventional hepatitis E and measured rHEV seroprevalence in a large diverse human serum cohort.

Patients with hepatitis (n=2018) were tested for rHEV RNA in the context of a real-world clinical service in Hong Kong. rHEV IgG seroprevalence in various risk groups was measured using a validated immunoassay. Commensal rats were tested for rHEV RNA and sequences were compared with human-derived strains.

From 2017 to 2025, 22 human rHEV infections were identified. Of these, 14 (63·6%) were immunocompromised compared to 22/78 (28·2%) conventional HEV patients (p<0.01). Hepatitis was milder in rHEV patients, but most immunocompromised rHEV patients progressed to chronic infection. Rat-derived rHEV belonged to two subtypes, one of which infected humans. Of 8294 individuals, 57 (0·7%) tested positive for rHEV IgG compared to 551 (6·6%) for HEV IgG. Increasing age predicted rHEV seropositivity (OR:1·03; 95% CI:1·01-1·05); persons with bloodborne pathogens did not exhibit higher rHEV seroprevalence.

rHEV is a sporadic cause of hepatitis in humans with disproportionate clinical significance for immunocompromised hosts. Although clearly linked to rat epizootics, routes of rHEV transmission remain enigmatic.