They discover a “corridor” between Africa and the European Mediterranean countries where West Nile virus circulates.

The scientific journal Nature Communications recently published the results of a study on West Nile virus carried out by the Italian Experimental Animal Prevention Institute Teramo in collaboration with the University of Trento, the Edmund Mach Foundation and the Pasteur Institute in Dakar (Senegal). . ). The study, which can be found at this link, traced the path of the virus between Europe and Africa.

History of the virus

West Nile virus (WNV), first isolated in 1937 from the West Nile region of Uganda, hence its name, has received increasing media attention in recent years, generating public interest and growing concern from public health authorities. The virus is present almost all over the world, including Africa, Western Asia, Europe, Australia and America.

Its reservoirs are wild birds and mosquitoes, mainly of the genus Culex, whose bites are the main means of transmission to humans. They bite infected birds, in turn become infected, and then again transmit the virus to other birds. By feeding on the blood of people, horses and various mammals, mosquitoes can transmit the virus. These latter recipients become “blind” random hosts; since their blood does not develop high concentrations of the virus, they cannot transmit it to other mosquitoes. Other documented modes of infection, although very rare, are organ transplantation, blood transfusion and maternal infections. – transmission of infection to a child during pregnancy.

In most cases, infection in humans is asymptomatic. Symptomatic cases (about 20%) are mild, comparable to the common flu, but more severe forms can affect the nervous system, especially in older adults or people with weakened immune systems.

Studying

A now published study examines the spread of WNV, revealing complex and unexpected routes connecting Africa and Europe. The researchers used advanced genetic and phylogeographic analysis to reconstruct the evolutionary dynamics of different West Nile virus strains across time and space. The combination of both methods allowed the virus to be traced, providing detailed information about its origins and how it spread over time. In particular, research has focused on two major virus lineages, L1 and L2, which have different trajectories and evolutionary histories.

“Our task as researchers is to understand the patterns of transmission in order to plan preventive measures. Prevention is a fundamental weapon because there is no vaccine that protects people from the virus: for example, it should be avoided as much as possible. mosquito bites as much as possible, using skin repellents, household insecticides and staying in areas protected by mosquito nets,” commented Nicola D’Alterio, Director General of the Experimental Animal Prevention Institute of Teramo.

Researcher Giulia Mencattelli, first author of the study, points out an interesting finding regarding line 1: “There is a real ‘corridor’ between Senegal, Morocco and the European countries of the western Mediterranean such as Portugal, Spain, France and Italy. , but according to “Our analysis is not a one-way corridor: there are also incursions that go from Europe to Africa.”

The head of the public health laboratory of the Teramo Institute, Giovanni Savini, coordinator of the research group, points out the different evolutionary dynamics of the two lineages: “According to the results obtained, it seems that L1 spreads more efficiently than L2, although they infect the same bird species and use the same the same vectors. The different susceptibility of birds to infection is only one of the possible factors responsible for these differences, since we still know little about the role of mosquitoes as vectors and their susceptibility. “These are all aspects of the virus life cycle that are still poorly understood and which we intend to study.”

It is the combination of viral genetic data with information on the movements of migratory birds and the susceptibility of different species to infection that will lead to a better understanding of how the virus spreads, with the aim of predicting and mitigating the impact of future epidemics. representing a research model for other new viruses.