First Evidence of Spillover of <i>Rocahepevirus ratti</i> Into Humans in Thailand

<i>Rocahepevirus ratti</i> (hepatitis E virus [HEV]-C), originally discovered in rats in 2010, has been recently linked to hepatitis in humans. Although rare and typically detected in the immunocompromised, much like <i>Paslahepevirus balayani</i> (HEV-A), it can manifest as acute or persistent hepatitis. In a next-generation sequencing (NGS)-based screen for causes of acute febrile illness (AFI) in Thailand, we assembled a complete <i>Rocahepevirus</i> (rat HEV [rHEV]) genome from a patient admitted to the hospital who developed abnormal liver functions 2-3 months after a heart transplant. Despite withdrawal of medications suspected of inducing hepatitis, he progressed from parenchymal liver disease to cirrhosis. The absence of other viral etiologies suggested rHEV may have been the cause of chronic hepatitis. Thailand strain Ma617-09869 is the sole human representative in a clade of genogroup C1 composed of sequences found in rats from Thailand and neighboring Southeast Asian countries, including Laos, Cambodia, Vietnam, and Indonesia. Principal component analysis (PCA) of viral sequences indicates humans are incidental hosts and suggests that white bellied rats (<i>Niviventer</i> spp.) are the putative original host, with black and common rats (<i>Rattus</i> spp.) serving as the natural reservoir. While <i>Rocahepevirus</i> adaptation may not currently facilitate human-to-human transmission, specific diagnostics are needed to identify additional sequences and cases, not only to gain a better understanding of the biology of this virus, but also to assess the risk for continued evolution, virulence, and increased zoonotic events.