Emergence of novel recombinant GII.P16_GII.2 and GII. P16_GII.4 Sydney 2012 norovirus strains in Italy, winter 2016/2017.

In the winter season 2014/15, the GII.P17_GII.17 norovirus strain Kawasaki 2014 emerged in Italy, cocirculating with pandemic GII.4 strains. In March 2016, molecular investigation identified novel GII.P16 recombinant noroviruses in children with gastroenteritis in Italy. In 43.10% of the genotyped noroviruses GII.P16 strains were identified: 12 were characterized as GII.2 and 13 as GII.4 Sydney 2012 capsid genotypes. The GII.P16 genotype became predominant in January- February 2017 along with an increase in norovirus activity. The capsid gene was characterized as GII.2 or GII.4 Sydney 2012 variant. The emergence of two different recombinant GII.P16 viruses, of which one harboring a pandemic GII.4 capsid sequence, suggests the potential for a future pandemic.