Researchers have now been able to produce reliable maps of the Zika infection risk for South America for the first time.
The spread of viruses like Zika depends on an array of factors. Environmental factors play a role as well as socio-economic ones. There have been several attempts to predict the risk of transmission of the Zika virus at a global and local level, but the spatial and temporal patterns of transmission were not yet well understood, until now.
In the vast majority of cases, mosquitoes of the genus Aedes transmit the Zika virus to humans. The main vectors are the Aedes aegypti and the Aedes albopictus. Both mosquito species are widespread in South America. In Europe, the Aedes aegypti is almost non-existent, whereas the Aedes albopictus is already very widespread in the Mediterranean region.
"With our new modeling techniques we can identify the risk areas for Zika infections in Latin America," said Sven Klimpel, Professor of Parasitology and Infection Biology at Frankfurt's Goethe University and at the Senckenberg Biodiversity and Climate Research Centre.
"In addition, we are now also able to depict Zika risk areas in Europe using the models. Our models also picture, for example, two autochthonous cases in southern France in the Var Département". At the end of October, French authorities reported the first Zika case in Europe, and about a week later a second case was announced. In Europe, the possibility of infection is present in the Mediterranean area, but it also exists in the French interior and in the Rhine area of Baden-Württemberg, Germany.
In order to determine the risk of infection in a specific area, the researchers led by Dr. Sarah Cunze and Prof. Dr. Sven Klimpel modeled the potential distribution of the two mosquito species. Since mosquitoes can only transmit the Zika virus if the virus is present in a region, the researchers included an evidence consensus map in their risk model. The map categorizes the number of reported Zika diseases on a regional level.
In addition, they included the average temperature of the warmest yearly quarter in the model, since the temperature has a decisive influence on whether the virus can survive and multiply in the mosquito. Finally, the scientists added socio-economic factors such as population density (the higher it is, the higher the risk of transmission) and gross domestic product, also positively correlated to the risk of transmission.