Detection of Norovirus GII.17 Kawasaki 2014 in shellfish, marine water and underwater sewage discharges in Italy

Norovirus (NoV) is a major cause of non-bacterial acute gastroenteritis worldwide, and GII.4 are the predominant human genotypes. Recently, a novel variant of NoV GII.17 (GII.P17_GII.17 NoV), termed Kawasaki 2014, has been... [ view full abstract ]

Norovirus (NoV) is a major cause of non-bacterial acute gastroenteritis worldwide, and GII.4 are the predominant human genotypes. Recently, a novel variant of NoV GII.17 (GII.P17_GII.17 NoV), termed Kawasaki 2014, has been reported as cause of gastroenteritis outbreaks in Asia, replacing the pandemic strain GII.4 Sydney 2012. This variant has also been reported sporadically in patients with gastroenteritis outside of Asia, including Italy.

In this study, 384 shellfish samples were tested for human NoVs using real-time PCR. A total of 52 samples positive GII NoV, selected as representative of different areas and sampling dates, were further amplified by conventional PCR targeting the capsid gene, and 40 samples were characterized as GII.4 (n=29), GII.2 (n=4), GII.6 (n=2), GII.12 (n=2), and GII.17 (n=3). Sixty-eight water samples (39 seawater samples from the corresponding shellfish production areas and 29 water samples from nearby underwater sewage dischargs) were also tested using the broad range assay: eight samples were characterized as GII.1 (n=3), GII.2 (n=1), GII.4 (n=2), and GII.6 (n=2).

A novel RT-PCR nested assay specific for GII.17 NoVs was used to re-test the characterized shellfish (40) and water (8) samples, and GII.17 NoV (Kawasaki 2014) was identified in 17 additional shellfish samples and in one water sample. Our results indicate that, in food and water matrices, broad-range assays may underestimate the prevalence of some, less common, NoVs.

The detection of the GII.17 strain Kawasaki 2014 in water and food samples in Italy highlights the need for more systematic surveillance for future disease control and prevention.