Scenari di diffusione e controllo di una pandemia influenzale in Italia

To investigate the spread of a pandemic strain of influenza virus through Italy and the impact of control measures, we introduce a SEIR deterministic model, with a stochastic simulation component. We assume for the pandemic an R0 (the basic reproductive number) of 1.8, with an average attack rate of 35%. We modelled the impact of control measures as vaccination (two doses of pandemic vaccine, or one dose of vaccine antigenically similar to the pandemic virus pre-pandemic followed by a dose of pandemic vaccine), antiviral prophylaxis and social distancing including school closure, and different type of quarantine measures. In absence of control measures, the epidemic threshold will be reached approximately 4 months after the importation of first cases, and the epidemic will be over in 7 months. The considered interventions, when independently implemented, reduce the cumulative attack rate to approximately 24%, at their best. Multiple interventions involving pre-pandemic vaccination, antiviral prophylaxis and social distancing measures, reduce the overall attack rate to 10%. In accordance with international findings, our results highlight the need of respond to pandemic with various preventive measures. Preparedness is therefore crucial, in order to organise all the control measures necessary to face emergency.