Retrospective study reveals the circulation of norovirus genotype GII.P21-GII.2 in Romania

Noroviruses are the leading cause of acute gastroenteritis, causing significant economic burden globally. Infection is self-limiting, occurring as sporadic cases or producing outbreaks associated with consumption of contaminated water or food. All age groups are affected and person to person transmission is frequent. Except a recent outbreak in Romania caused by the emergent genotype GII.P17-GII.17, few data regarding the circulation of noroviruses in our country are available. We retrospectively analyzed stool samples from acute gastroenteritis patients hospitalized in Romania between 2005 and 2008. Noroviruses were detected by RT-PCR and phylogenetic analysis was inferred from partial sequences spanning ORF1 and ORF2. Recombinant GII.P21-GII.2 isolates were found in two adult patients from a cluster of acute gastroenteritis in 2006. Molecular analysis based on partial genomic sequences indicated high degree of similarity between the two isolates and grouped them with cosmopolitan strains circulating in the same period of time. Along with the high rate of mutation, recombination is an important driving force in norovirus evolution. GII.P21 isolates, formerly known as GII.b recombinants, have been detected in Europe since 2000 and associated with sporadic cases and outbreaks of gastroenteritis worldwide. This is the first work describing norovirus GII.P21-GII.2 identified in Romania.