Norovirus outbreaks in Abruzzo region during 2017

Abstract

Purpose: Norovirus (NoV) is a pathogen frequently involved in non-bacterial gastroenteritis, causing diarrhea and vomiting in millions of cases worldwide annually. Transmission is mostly determined from person to person. However, NoV infection has additionally been associated with the consumption of raw shellfish or as a consequence of foodstuff contamination during processing or serving. A systematic review of outbreaks attributed to NoV between March and June 2017 in Abruzzo region was conducted to assess the contribution of NoV epidemiology in the human disease. Methods & Materials: Ninety-eight fecal samples and 137 environmental swabs were analysed from three different settings: one restaurant, one bar and one long-term care facility. The analysis for the detection of Norovirus Genogroups I and II (NoVGI and GII) were conducted in accordance to the ISO 15216-2 2013, with modifications. The positive samples were assayed for NoV genotype, using Nested PCR. Results: Overall, the prevalence of positive samples for the detection of NoV RNA was 44.4%. Among these, NoVGI was present in 0.4% of the samples and NoVGII in 44%. In particular, NoV genotype GII.2 was present in 4.1%, while the GII.4vSydney 2012 in 39.9% of the samples. The results obtained from the restaurant showed the presence of NoVGII.2, while NoVGII.4vSydney 2012 strain was detected in outbreaks occured in the bar and in the long-term care facility, suggesting some correlation between these, also enforced by the same period in which the disease spread (March 2017). Different was the period of outbreaks at the restaurant (May-June 2017), supported by a diverse NoVGII subtype (NoVGII.2), confirming no correlation between the previous ones. Conclusion: Person-to-person close contact, contaminated food and environmental surfaces were the probable transmission routes for the Abruzzo NoV outbreaks in 2017. The poor personal hygiene habits play an important role in the secondary spread of foodborne viral infections and, for this reason, it is very important to enhance surveillance systems and prevention procedures. Moreover, it would be useful to adopt surveillance systems involving food, environmental and clinical matrices, in order to facilitate activities of source attribution and for the prevention and control of potential epidemics.