Uncommon G9P[4] group A rotavirus strains causing dehydrating diarrhea in young children in Italy.

Group A rotaviruses (RVA) are one of the major cause of acute gastroenteritis (AGE) in young children, being responsible for up to 250.000 deaths worldwide, mostly in developing countries. The two outer capsid proteins VP7 (glycoprotein, G-genotype) and VP4 (protease-sensitive protein, P-genotype) are the basis for the binary RVA nomenclature. Although at least 36 G-types and 51 P-types of rotavirus are presently known, most RVA infections in humans, worldwide as well as in Italy, are related to six major G/P combinations: G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. In November 2016, in the framework of the Italian 2016/17 rotavirus surveillance season, a total of 22 rotavirus-positive samples from hospitalized children presenting AGE symptoms were collected in a small area of Central Italy (Ancona, Marche). After genotyping, 3 samples presented the G9P[4] genotype. In order to better understand the origin of these uncommon RVA strains causing dehydrating diarrhea in three children, the strains RVA/Human-wt/ITA/AN18/2016/G9P[4], RVA/Human-wt/ITA/AN19/2016/G9P[4] and RVA/Human-wt/ITA/AN22/2016/G9P[4] were subjected to nucleotide sequencing of all the 11 gene segments to define their genomic constellation. Nucleotide sequencing revealed that the genomic constellation of the three strains was G9-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2, highlighting human origin for all the gene segments investigated. The molecular characterization of RVAs and the continue monitoring of their circulation is needed to better define the epidemiology of these pathogen and to detect the emergence of viral variants presenting a high spreading potential in humans in the post-vaccination era.