Mosquito on a person's arm PHILIPPE HUGUEN / AFP Why are some people like "magnets" for mosquitoes, while others seem to get rid of them? According to scientists, who are still working to decipher its mechanisms, behind this attraction - sometimes fatal - lies a complex and variable chemical mixture. "Of just over 3,500 species of mosquitoes known, around a hundred bite humans and half a dozen are vectors of diseases" such as malaria, dengue, yellow fever, chikungunya, zika or the West Nile virus, explains to AFP Frédéric Simard, director of studies at the Institute for Research for Development (IRD), in southeastern France. And "it's not a myth: we're not all the same when it comes to mosquitoes' appetites. But we're also not magnets all the time," added this medical entomologist. Humans attract these tiny vampires, including the famous tiger mosquito, through multiple sensory signals, mainly body odors, carbon dioxide from breath and heat, experts agree. Female mosquitoes - the only ones that bite - detect them through specialized receptors and this is how they choose their target. "We have known for more than 100 years that mosquitoes are attracted to the carbon dioxide we exhale: it is the first signal that triggers their behavior, at several tens of meters", Rickard Ignell, author of a recent study on the chemical foundations of the differential attraction of these insects to human breath, explained to AFP. At about 10 meters, "mosquitoes begin to detect our odor which, combined with CO2, attracts them even more", added this Swedish scientist. Popular beliefs However, several popular beliefs about what attracts these dipterans have been debunked. "The difference between blood groups does not have a solid scientific basis: some studies have been carried out, but with very few people. It is also not related to the color of the skin, eyes or hair", said Simard, from IRD. A fundamental attraction factor is, without a doubt, the smell, "a mixture of molecules produced by our microbiota and more or less attractive to mosquitoes", agreed the entomologist. Humans emit between 300 and 1,000 different odorous compounds, several studies have shown, but scientists are just beginning to better identify which ones attract these small blood-sucking animals. For the research in which Ignell participated, the difference in the attractiveness of 42 women to the "Aedes aegypti" mosquitoes, vectors of yellow fever or dengue, among other diseases, in vast regions of Latin America was evaluated in the laboratory. "We demonstrated that a mixture of odorous compounds - we identified 27 that these mosquitoes can detect - influences the degree of attraction", according to the scientist. "The women most attractive to mosquitoes, especially those in the second trimester of pregnancy, produced a little more of a compound derived from the degradation of sebum", he considered. Precisely, the fact that such a small increase in the released dose of 1-octen-3-ol, also known as fungus alcohol, changes the behavior of these insects was one of the surprises, revealed Ignell, adding that "mosquitoes are fascinating creatures". Now on g1 Be careful with alcohol Drinking beer, which increases body temperature, the amount of CO2 exhaled and changes skin odors, can also contribute to attracting them more, according to some studies. One of them, standardized, carried out in Burkina Faso with volunteers who drank a local beer and, a few days later, the same amount of water, demonstrated that the Anopheles mosquito, the main vector of malaria, was more attracted to the odors of those who had consumed the alcoholic beverage. These mechanisms are fueling growing research as the health threat related to some of these insects expands. The tiger mosquito, in particular, is expanding into areas where it was not endemic due to global warming, urbanization and globalization. "The risk affects more and more people, and also more countries where there is money to protect themselves, which generates funding and research results", assured Simard. When mosquitoes are around, it is recommended to protect yourself from bites with long, loose clothing, mosquito nets or repellents. "And try to eat lightly and consume alcohol in moderation," added the scientist.