Detection and full genomic sequencing of rare hepatitis E virus genotype 4d in Italian wastewater, undetected by clinical surveillance.

Hepatitis E is a liver disease caused by the hepatitis E virus (HEV), primarily transmitted through contaminated water or food. There are four different HEV genotypes in humans, with genotypes 1 and 2 being the most widespread. Genotypes 3 and 4 are found in animals and can also infect humans. Genotype 4 is prevalent in Asia, mainly in China. In Italy, only one outbreak of HEV-4 has been documented, which occurred in 2011, involving five patients. In 2013, HEV G4 was also detected in a pig farm. Since then, no further evidence of HEV genotype 4 has been found in the country. This study describes the first detection of HEV genotype 4, subtype d, in wastewater in central Italy, despite a lack of any clinical case reported in the area. By using a multiplex PCR protocol and two sequencing strategies, Illumina and ONT, the virus's complete genome was sequenced and characterized as subtype 4d. These findings shed light on the potential of environmental surveillance for infectious agents to improve our understanding of epidemiology and support public health efforts.