First the rains, now the heat. And mosquitoes proliferate to incredible levels. So much so that the scientific director of the Venetian experimental zooprophylactic institute warns: “They will be triple compared to last year, when the spring was particularly dry”. A risk, especially from a health point of view.
Because, in Veneto – and in Polesine in particular – the presence of mosquitoes, for almost fifteen years now, has meant a West Nile risk. “Nile fever” particularly affects the elderly and the weakest, and can have lethal consequences. In 2018 the worst year, when 45 cases of West Nile were recorded in Polesine, with 15 neuroinvasive forms of the disease and, unfortunately, five deaths. Since then, massive prevention efforts have drastically reduced the number of cases. Last year, then, a new surge with 36 total infections, 12 of which were serious.
And this year – among other things, the first year in which each Municipality has to organize its own disinfestation, until last year managed by the Ulss for the entire provincial territory – there is a risk of a new resurgence of the virus.
According to the alert issued in recent days by the European Center for Infectious Diseases, in fact, “Europe is experiencing a trend of rising temperatures with more frequent and severe heat waves and floods. Summers get longer and hotter. This creates favorable conditions for mosquitoes.” And if the increase in the number of mosquitoes increases (“they are already triple last year”, underlined by the IZSV) “we expect more cases, and possibly deaths, from diseases such as Dengue, Chikungunya and West Nile fever”. precisely.
In the meantime, all that can be done is to monitor the situation: an observation work that is done by taking samples from mosquito pools but also by analyzing the health status of migratory birds, the first to be infected by the virus. The bulletin released on Thursday by the Istituto Superiore di Sanità sets the confirmed cases of West Nile, in Italy, at three in this first part of the season: none in Veneto. In particular, a magpie in the province of Ravenna and a crow in the province of Varese were found to be infected, while the only pool of infected mosquitoes was found in Catania.
In Polesine, in recent years, the first alarm bell came on average around mid-July, while cases of human contagion have always concentrated after August 15th.
West Nile, caused by the homonymous virus, is transmitted by the bite of infected mosquitoes to humans and animals, generally horses and birds. Mosquitoes belong to the genus Culex (species pipiens), while over 70 species of birds have been identified as reservoirs of infection, especially passerines and corvids, where the virus can persist from a few days to a few months.
Most infected people do not experience symptoms (80%). The symptomatic forms are manifested by mild flu-like symptoms, fever, headache, muscle-joint pain, rarely accompanied by skin rash. Less than 1% develop neuroinvasive disease, such as meningitis, encephalitis, or flaccid paralysis. The risk of neuroinvasive disease increases with age and is highest among adults over 60 years of age.