The Italian Rotanet Surveillance Program. Rotavirus genotypes among children hospitalized with severe gastroenteritis, 2007-2012.

Background. Rotavirus is the major cause of acute gastroenteritis in infants worldwide. The ISS in collaboration with the Ministry of Health has implemented a nationwide laboratory based surveillance of acute rotavirus gastroenteritis in Italy to investigate the diversity of rotavirus strains circulating before the introduction of large scale vaccination. RotaNet-Italia is linked to the EuroRotaNet network, including 17 European diagnostic laboratories. Methods. From January 2007 to July 2012, approximately 5700 rotavirus positive stool samples were collected from hospitalized pediatric patients with acute diarrhea in 13 Regions. After viral RNA extraction, samples were genotyped for VP7 (G-type) and VP4 (P-type) genes by reverse transcription and multiplex-PCR, using type-specific primers. Results. Significant variation in the frequency of different rotavirus genotypes was observed between different years and areas of Italy. Most strains belonged to genotypes G1-G4, and G9, associated with either P[8] or P[4], commonly found in humans worldwide. However, in at least 2% of cases, unusual or novel strains, such as G1P[4] and G10P[8], were also detected, suggesting gene reassortment events between rotaviruses of different origin. Mixed infections with two or more rotavirus strains were observed frequently (8% of patients). Conclusions. Data of RotaNet-Italia confirm the genetic diversity of rotaviruses circulating in Italy and the existence of differences between Regions. Although overall data confirm the suitability of present vaccine formulations, novel strains are also shown to emerge occasionally in Italy, associated with possible reassortment and zoonotic transmission. Rotavirus surveillance is valuable to confirm vaccines appropriateness and control possible emergence of novel strains.