Rotavirus gastroenteritis : epidemiological dynamic and relationship between the disease outbreak and environmental factors

Rotavirus is a double stranded RNA virus which belongs to the family Reoviridae. Nowadays, eight strains of this virus are known, named, in alphabetical order, from A to H, but it seems that only the genotypes A-C infect humans, with the majority of the diseases caused by the type A. The illness associated with the rotavirus is a gastroenteritis which provokes diarrhoea and fever. In the most severe cases, it can lead to dehydration of the patient. The main target are infants from the 3rd month of age and children younger than 5 years, but it can affect also adults, although in a milder form. The infection route is the faecal-oral one, that can happen via direct person- to-person contact, ingestion of contaminated food or water and contact with infected fomites or surfaces. Also the air is suspected to be a route for the rotavirus disease, but there is still no evidence that it actually works on humans. It is a relevant problem because it is a disease widespread all over the world, and it accounts of around 453000 deaths worldwide every year. For now, it does not exist an antiviral therapy, but in 2006 a vaccine has been released in the United States, with positive results. It is hard to study the rotavirus in laboratory because it is highly unstable, so even the act of observing it in a sample brings to a different behaviour from the one in the natural environment. In this thesis the infection mechanism is investigated using an epidemiological model, which simulates the incidence of the disease in a community, with a focus on the effect of the environmental contact rate, the birth rate and the amplitude of the seasonality of both the direct person-to-person contact rate and the mortality of rotavirus. It results that the birth rate is an important factor which influences the stability of the system and that the environmental route of infection through the local water reservoir cannot be neglected, although the main route remains the direct contact with infected people.