Impacte i control dels brots de gastroenteritis per norovirus a Catalunya (2017-2019) i estudi de la presència del virus a la saliva

Abstract

L’objectiu principal d’aquesta Tesi Doctoral és caracteritzar l’impacte dels brots produïts per norovirus al nostre país i investigar possibles millores de les opcions adreçades a controlar i reduir aquest impacte. Els objectius específics proposats s’agrupen en tres blocs: 1. Investigar les característiques epidemiològiques i els genotips responsables dels brots de GEA per HuNoV en institucions tancades o semi-tancades (residències geriàtriques, centres sociosanitaris, hospitals, guarderies, centres escolars, hotels, altres). 2. Avaluar la presència de HuNoV en mostres de saliva d’individus infectats, i estudiar la relació entre diversos factors (simptomatologia, estat secretor i edat) amb la seva presència a la saliva. 3. Dur a terme estudis de supervivència i inactivació vírica per a determinar l’efecte en els hàbits del consumidor més crítics per a la seguretat alimentària sobre el risc d’infecció per HuNoV.

Human noroviruses (HuNoV) are recognized as one of the main etiological agents causing acute gastroenteritis, being directly responsible for the 17-18% of the total cases and affecting all age groups. As an enteric virus with fecal-oral transmission, HuNoV is also a highly relevant virus in the field of public health and food safety. Outbreaks caused by HuNoV are particularly common in closed and semi-closed settings such as hospitals, nursing homes and schools. Epidemiological surveillance of HuNoV is not systematically performed and the total number of cases among the population may be underestimated. Molecular characterization of different genotypes associated with outbreaks provides information of the geographic and temporal distribution of HuNoV genotypes, and enhances the understanding of viral features which may affect HuNoV pathology and transmission. In this work, we characterized the circulating HuNoV genotypes among Catalan population causing outbreaks in different settings during a 3-year period (2017-2019), and correlated them with epidemiological data collected during outbreak investigations (mainly setting, type of transmission, season, attack rate, outbreak size and duration, and symptom information for affected individuals). HuNoV is routinely diagnosed by the molecular analysis of feces, although its presence has been also identified in the oral cavity. This hypothetic new diagnostic approach would be more attractive and alternative for its detection, making the sampling easier, faster and less invasive and risky. In these thesis, the occurrence of HuNoV in saliva of affected individuals was studied from a subset of outbreaks, and its correlation with clinical data regarding symptoms and other several individual characteristics were analyzed. - 10 -

Finally, a common route of acquiring HuNoV infection is through the consumption of contaminated food, especially if eaten raw or undercooked, or even if associated with the transfer of viral particles during food preparation by people who are in a period of shedding. Apart from bivalve mollusks, fruits and vegetables are increasingly being recognized as potential vehicles for their transmission, which can be contaminated at any point in the production chain. Therefore, proper washing treatments before consumption would be a major step in reducing viral particles in foods to mitigate risk of HuNoV transmission. The results of our work confirm the suitability of different disinfectants to reduce HuNoV contamination in vegetables and its proper application in the food industry. Moreover, they could also be potentially used in private homes, as well as in catering services, where implementation of food sanitizers should be strengthened.