Detection of norovirus in children with acute gastroenteritis in a hospital of Italy

Background: Noroviruses (NoV) are the main non-bacterial agents of acute gastroenteritis (AGE). Norovirus infection is characterized by a high attack rate due to a low infectious dose. The virus can be transmitted through droplets and fomites. To better understand the role and the incidence of NoV, laboratory-based surveillance was conducted on paediatric patients affected by GE admitted to the main hospital in Brescia (northern Italy). Methods: Over two years 448 stool samples (1 per patient) were collected from pediatric patients (except 4 nurses) affected by GE and admitted at the hospital of Brescia. Samples were processed for routinary tests (Salmonella spp., Campylobacter spp., rotavirus, adenovirus, astrovirus). Negative samples were further analyzed for NoV by random reverse transcription (cDNA) followed by 2 PCRs targeting both ORF1 and ORF1/ORF2 overlapping region. All PCR-positive samples were sequenced. Multiple infections were not investigated. Results: Of 448 stool samples, 227 proved negative for enteric bacteria, rotavirus, adenovirus and astrovirus. Among these, 88 (38.8%) were positive for NoV. Based on sequencing, 1 NoV GI and 7 NoV GII genotypes were identified. The most common was GII.4. GII.P4 v. Den Haag 2006b was detected in 4 nurses and shared 100% nt identity with the NoV strain detected in 5 young patients. Epidemiological investigation revealed that these patients acquired infections >24h after hospital admission. They were monitored by nurses that became sick (AGE) in the same week as the young patients. Conclusions: This study confirmed that NoV circulates among AGE-affected children and adults. Person to person transmission could have occurred between children and nurses. GII.4 is the most common genotype. Key messages: NoV is an important issue among AGE-affected children and adults. Specific guidelines for hygiene management are needful measures to reduce the impact of nosocomial NoV outbreaks.