A recent study published in Nature Communications reports that rat hepatitis E virus (ratHEV) may be infecting humans more often than previously recognized, raising questions about diagnosis, transmission, and the global impact of this infection.
The findings matter because hepatitis E is already known to cause millions of cases of acute hepatitis each year. The discovery that another virus—previously thought to only affect rodents—can also infect humans suggests there may be undiagnosed or misdiagnosed cases worldwide.
Researchers reviewed current evidence on ratHEV’s ecology, molecular biology, host range, and clinical effects. The study explains that while the Hepeviridae family was once considered host-restricted with no role in human disease beyond classic HEV infections, "this assumption was challenged in 2018, when human infection by a Rocahepevirus species was confirmed." Since then, additional cases have been identified through surveillance and retrospective analyses in Asia and Europe as well as Canada. This has led researchers to reconsider how widespread zoonotic transmission might be.
RatHEV is a positive-sense RNA virus with several genotypes; genotype C1 appears most likely to cross into humans. The study notes that "ratHEV is widespread in synanthropic rat populations" across Asia, Europe, and North America. It has also been detected at lower rates in other animals such as pigs and birds of prey.
Diagnosis remains difficult due to a lack of commercial assays for ratHEV; molecular testing for viral RNA is currently the most reliable method. Antibody-based tests are mainly useful for epidemiological studies rather than clinical diagnosis because cross-reactivity can complicate results.
Clinically, ratHEV infection can resemble classic HEV infections—from mild illness to severe liver failure—and can become chronic among immunocompromised patients. There are even reports linking it to conditions outside the liver such as encephalitis and glomerulonephritis. Treatment follows existing protocols for HEV: "Ribavirin is considered the main treatment; other antivirals exhibit in vitro activity but have not been assessed in humans." Some evidence suggests partial protection from an existing vaccine against classic HEV genotype 1 but more research is needed.
The authors conclude that knowledge about ratHEV’s effect on human health remains limited due to sparse surveillance outside China and Western Europe. They suggest including ratHEV guidance within broader hepatitis E recommendations could improve detection and encourage research investment.
