Detection and molecular characterization of noroviruses from five sewage treatment plants in central Italy

Noroviruses (NoVs) are the most frequent etiological agents of non-bacterial gastroenteritis. These viruses are transmitted through the fecal-oral route, leading to high viral loads in sewages. The objective of this paper was to study the environmental occurrence of the most prevalent NoV strains in different wastewater treatment plants. In addition, molecular characterization of the isolated strains was performed. Two different PCR-based methods were carried out and a novel strategy was used to verify the level of RT-PCR inhibition. From May to September 2007, a total of 97 inflow and outflow samples were collected from five wastewater treatment plants in central Italy. We detected NoV by nested PCR in 96.9% of influent samples: 89.1% contained both genogroups; 4.7% contained only GI and 3.1% only GII. In effluents, we detected NoV in 78.8% of samples: 30.3% contained both genogroups, and 48.5% contained only GI. The major genotypes detected by sequencing analyses were GI/2, GI/5, GII/b, GII/4 and GII/6. This work confirms the wide circulation of NoVs in Italy with a predominance of GI strains, and the widespread distribution of NoV variants in both raw and treated wastewater.