Molecular epidemiology study of Rotavirus in children with AGE in Lombardy (2011-2012)

Objectives: The region Lombardy (North-West Italy) participates to the RotaNet-Italy Study Group, which is a component of the EuroRotaNet rotavirus surveillance network. The sentinel regional hospitals of Lombardy are located in Cremona, Bergamo and Gallarate. In this study, group A rotaviruses (RVA) from cases of acute gastroenteritis (AGE) were investigated by molecular characterization methods with the aim of evaluating co-circulation of different viral strains, and describing the features of rotavirus infection in children. Methods: During 2011-12, 243 stool samples were collected from children <5 years admitted to the hospital with AGE and found positive for RVA by commercial rapid test. Approximately 62.6% of samples were from Cremona, 25.9% from Bergamo, and 11.5% from Gallarate. Molecular characterization of rotavirus strains, based on EuroRotaNet methods and algorithm, was performed by the ISS, which coordinates the national project. Results: All RVA strains detected belonged to “common” G (VP7) and P (VP4) genotypes: 88% of stool samples contained a single genotype, while multiple genotypes were observed in 11.5% of cases. No negative samples or “uncommon” genotypes were found, and only 0.4% of samples were G-untypable. Overall, the most frequent combination was G1P[8] (46.9%, range: 27-71.4%) followed by G4P[8] (17.7%, range: 10.7-36.5%), G2P[4] (11.1%, range: 0-14.3%), G9P[8] (7.8%, range: 3.2-10.7%), and G3P[8] (4.5%, range: 0-9.2%), similar to other Italian regions and European countries [1]. The rate of RVA-AGE was highest in the 0-36 months age group, where the cumulative prevalence was 80.9%. In particular, 43.4% of episodes occurred between 6-12 months of age, as previously reported in Italy [2]. Evaluation of the symptoms associated with RVA-AGE showed that 67.5% of children had fever >38 °C, 69% diarrhea > 3/die, and 69.4% presented vomiting associated with diarrhea. Conclusions: The present study shows that different rotavirus strains were associated with RVA-AGE among children presenting at different sentinel hospitals throughout Lombardy. RVA-AGE occurred mostly in children <3 years, in particular in the age group 6-12 months. Rotavirus 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 absence of such findings during this investigation does not exclude possible future emergence of unusual RVA strains in Lombardy. It is therefore important that countries and regions conduct active rotavirus molecular surveillance [3]. Continuation of RVA monitoring activities by the RotaNet-Italy Study Group can help define a national and regional baseline of circulating rotavirus genotypes before mass vaccination, and assess possible strain selection where rotavirus vaccines are in larger use. 1. Ruggeri FM, et al.; RotaNet-Italy Study Group. Molecular characterization of rotavirus strains from children with diarrhea in Italy, 2007-2009. J Med Virol. 2011; 83(9):1657-1668 2. Van Damme P, et al.; REVEAL Study Group. Multicenter prospective study of the burden of rotavirus acute gastroenteritis in Europe, 2004-2005: the REVEAL study. J Infect Dis. 2007; 195(1):S4-S16. 3.Santos N, Hoshino Y. Global distribution of rotavirus serotypes/genotypes and its implication for the development and implementation of an effective rotavirus vaccine. Rev Med Virol. 2005; 15(1):29-56.