Molecularand clinical surveillance of rotavirus infection in children with acute gastroenteritis in Northen italy (2007-2013)

Purpose. Since 2007/2008 winter season, the Lombardy region (Northern-Italy) participates to the RotaNet-Italy study group, part of the European Rotavirus Surveillance Network (EuroRotaNet). The main goal of the network is to study group-A rotaviruses (RVA) strains distribution, to survey the eventual emergence of uncommon strain and to describe the features of RV infection.Methods & Materials. During 2007-2013, 699 positive-RVA stool samples were collected from children with acute gastroenteritis admitted to hospitals in Lombardy. Molecular characterization of RVA, based on EuroRotaNet methods and algorithms (Fig. 1), was performed by the Istituto Superiore di Sanità (ISS), which coordinates the project at national level. Results. 99.5% of RVA detected belonged to “common” G (VP7) and P (VP4) genotypes: about 88% of specimens contained a single genotype, while nearly 12% of samples presented multiple genotypes. Three negative samples and two “uncommon” genotypes (G10P[8] and G2P[8]) were found in 2008/2009 season, and 0.4% of samples were G-untypable. The combination most frequently detected was G1P[8] (48.6%) followed by G9P[8] (17.6%), G4P[8] (11.4%), G2P[4] (6.4%), and G3P[8] (3.8%). Interestingly, G9P[8] detections decreased progressively from 2007/2008 to 2011/2012, while the genotypes circulated at high extent in 2012/2013 (Fig. 2). 67% of all RVA infections occurred from January to April, as expected (Fig. 3). Most (about 60%) infections were reported in children ≤2 years of age, particularly in children ≤1 years (~33%). About 60% of children had diarrhea for > 3/die, 62% fever >38 °C, and 67% presented diarrhea and vomit. Conclusion - The results of this surveillance study showed that different rotavirus strains circulated mostly in children ≤2 years, with a relevant impact in those aged ≤1 years. RVA has been reported to undergo reassortment and mutation, and zoonotic transmission from animals to humans can also happen, generating new strains with uncommon antigenic and virulence characteristics. The presence of uncommon genotypes here, underscore such findings and possible future emergence of unusual RVA strains. The persistence and implementation of RVA surveillance by the RotaNet-Italy study group can help define the epidemiological profile of circulating RVA genotypes before the introduction of mass vaccination, and assess possible strain selection when RVA-vaccines will be introduced at higher extent.