Combining data from surveillance on mosquitoes and corvids to understand the factors affecting the dynamics of West Nile Virus in Emilia-Romagna, Italy
West Nile Virus (WNV) is now endemic in Northern Italy (as well as in many European countries), with a yearly number of recorded human cases oscillating between few tens up to around 600 in 2018 and 2022. Humans actually are dead-end hosts, while the infection is transmitted between Culex mosquitoes and several species of birds. The region Emilia-Romagna (one of the most affected areas) has in place since 2013 an extended surveillance program of both mosquitoes and corvids. We have analysed these data through an SEI-SEIR model where several parameters depend on temperature, as shown in laboratory experiments, while over-wintering occurs through infected diapausing mosquitoes. We found that an essential factor determining human risk is spring temperature, as confirmed also by a statistical analysis of European data. Another important factor for epidemic dynamics in a given year is pre-existing immunity in birds; as no serological data exist, we reconstructed the trend of seroprevalence over the years, which however has no clear relation with epidemic intensities. Joint work with Alex De Nardi, Giovanni Marini, Francesco Menegale, Marco Tamba