Rocahepevirus ratti: molecular evolution, zoonotic potential and public health impact.

Rocahepevirus ratti (ratHEV) is now recognised as an emerging zoonotic cause of hepatitis E, entrenched in urban rodent populations and already implicated in more than 50 confirmed human cases across Asia and Europe. Spillover occurs even in the absence of reported rodent contact, pointing to indirect environmental routes that remain poorly defined. Most infections are self-limiting, but acute hepatitis can be severe or fatal, and in immunocompromised patients ratHEV can persist and progress to chronic hepatitis. The absence of specific serological assays and the suboptimal performance of current molecular protocols, compounded by the high genetic diversity of the virus, limit the sensitivity of case detection. These challenges, together with limited awareness among health professionals, mean that the true magnitude of ratHEV globally remains unknown. This Review synthesises current knowledge on ratHEV ecology, host range, molecular virology and clinical impact, and outlines priorities for improving diagnostics, surveillance and prevention strategies.