West Nile virus news in France
The infection, mainly transmitted by the Culex mosquito, can cause symptoms such as fever, headache, muscle and joint pain, vomiting, diarrhea or rash. In severe cases, life-threatening encephalitis can occur.
A Culex pipiens mosquito, vector of the West Nile virus / Credit: Fabrizio Montarsi
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West Nile virus news in France
The number of cases of infection with West Nile virus (WNV, or West Nile virus), a viral species of the genus, continues to grow in France Flavivirus – which also includes zika and dengue fever – mainly transmitted by mosquitoes Culex, although the main hosts of the virus are birds. Last week, according to data from the bulletin of the Istituto Superiore di Sanità (ISS), 71 new cases were confirmed and 2 deaths were reported, for a total of 301 infections, including 5 fatal, from the first case reported to the beginning June, in the province of Padua. Besides Veneto, the main regions affected are Piedmont, Lombardy, Friuli-Venezia Giulia and Emilia-Romagna, although some infections have also been recorded in Tuscany and Sardinia. At European level, several cases have also been reported since the start of this summer season in Greece, Austria, Romania and Slovakia, as well as dozens of cases in neighboring countries. Almost all West Nile virus infections recorded in France have occurred in the symptomatic form of the disease, which presents with symptoms such as fever, headache, muscle or joint pain, vomiting, diarrhea or rash, although more than half of the cases (160 out of 301) unfortunately developed an attack of the central nervous system, therefore a disease in its neuro-invasive form, which in the most serious cases can lead to fatal encephalitis.
Although it is a known virus (first isolated in 1937 in Uganda, in the district of West Nile from which it takes its name, and reported beyond Africa, also in the States United States, Canada, Mexico, Central and South America, the Caribbean, Africa, Middle East, Southern Europe, Russia, India and Indonesia) there is currently no vaccine that protects once morest infection or disease, prevention therefore consists above all in reducing exposure to mosquito bites, for example by using repellents, by wearing clothing that covers the body as much as possible when outdoors, especially at sunrise and sunset Sun. It is also recommended to frequently empty flower pots and other containers and to avoid standing water. It is precisely these, in an environmental and climatic situation like that of the summer of 2022, which determine a favorable context for the circulation of the virus.
Because drought increases the spread of West Nile virus
Contrary to what one might think, the low rainfall in recent months is contributing significantly to the spread of West Nile virus which, as noted, is an avian virus that is transmitted to humans through mosquito bites. infected. Stagnant water is the ideal environment for the proliferation of mosquitoes, but because of the drought, the same mosquitoes have less easily found damp places to breed, going more often to share the same areas where birds, especially migratory ones, they meet to drink or nest. ” This situation has multiplied the chances of encounters between the reservoir of the disease (birds, editor’s note) and the vector of the disease (mosquitoes, editor’s note).As biologist Fabrizio Montarsi of the Experimental Zooprophylactic Institute of Veneto explains.
Therefore, in the most humid areas, reduced by a particularly dry summer, the highest incidence of human cases is recorded. The disease can also affect horses, and that is why in addition to monitoring human cases, veterinary surveillance is also active, carried out on horses, mosquitoes, sedentary and wild birds, which has confirmed the circulation of the virus. West Nile in these animals in Piedmont, Veneto, Friuli-Venezia Giulia, Emilia-Romagna, Lombardy and Sardinia.
West Nile, incubation time and symptoms of the disease
From the moment of a bite from an infected mosquito, the incubation period varies between 2 and 14 days, but in subjects with special health conditions, such as an immune system deficiency, it can also extend up to 21 days. Most people (4 out of 5) infected with West Nile virus have no symptoms of the disease, while of symptomatic cases, 20% have mild symptoms, such as fever, headache, muscle and joint pain , vomiting, diarrhea, enlarged lymph nodes. and skin rashes.
These symptoms, underlines the ISS, can last a few days – in rare cases a few weeks – they can vary greatly depending on the state of health and the age of the person. Older people and people with chronic conditions (such as diabetes and hypertension) are at higher risk of developing more serious disease.
The most severe symptoms occur on average in less than 1% of those infected and include high fever, severe headache, muscle weakness, disorientation, tremors, visual disturbances, numbness, seizures, which can range from up to paralysis and coma. In severe cases (regarding 1 in a thousand), the virus can cause encephalitis (inflammation of the brain) which can be fatal.
