Should you be wary of mosquitoes?

Q: “I wonder if mosquitoes and other biting insects could be vectors of contagion when the good weather returns?” wants to know Vincent McCormack. With spring and the snow melting, several readers have sent us this question. So let’s see …
A: There is a tendency to think that mosquitoes can spread just about any disease by biting sick people and transporting contaminated blood to other people. But in general, it’s really not that easy for a virus to be transmitted by mosquitoes.

First, we read on the site of the journal Nature , the “mouth” of mosquitoes is made up of six different parts, four of which are used to penetrate the skin. The other two are made like tubes: one for injecting saliva, the other for drawing blood. But there is generally no blood transfer during the bite: only saliva is inoculated and, if it does not contain a virus, no disease is transmitted.

Some viruses have evolved to be spread by insect bites, for example by being able to reproduce in the salivary glands of certain mosquito species, but this is absolutely not the case with COVID-19 – and the rule general is that the viruses swallowed by mosquitoes are digested like the rest of the blood.

A mosquito can still transfer contaminated blood from one person to another if it bites the carrier of a disease and then bites someone else very soon after, adds Benoît Barbeau, virology researcher at the ‘UQAM. But even in such a case, he says, “the chances of having COVID-19 because of it are virtually non-existent.” Viruses are very specialized beings that can only infect certain specific types of cells, which have the “right” receptors on their surface. COVID-19 is only capable of infecting the mucous membranes of the nasal passages and the upper lungs, places in the body which are much more easily accessible by inhaled droplets than by passing through the blood.

In the blood, viruses are recognized by the immune system called “innate” (unlike antibodies, which are “acquired”) and it would take a very large dose of COVID-19 to contract the disease through the blood.

In short, we will not have to worry about mosquitoes more than usual this summer.

Q: “Can migratory birds, which will arrive very soon, be carriers of COVID-19?” asks Jana Lavoie.

A: “Not at all. From what we know about this virus, birds do not transmit it, ”says Mr. Barbeau. The “animal reservoir” (the species that permanently harbors the virus and from which it made the leap in humans) has not yet been identified with certainty, but the suspicions relate mainly to bald people -mice from China, not migratory birds.

These are sometimes the cause of “zoonosis”, the passage of an animal microbe to humans, but they are mainly associated with influenza, and not with coronaviruses.

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COVID-19 raises a lot of questions. In order to respond to as many people as possible, science journalists have decided to join forces. The media members of the National Cooperative of Independent Information ( Le Soleil, Le Droit, La Tribune, Le Nouvelliste, Le Quotidien and La Voix de l’Est ), Québec Science and the Center Déclic team up to answer your questions . You have some? Write to us . This project is made possible thanks to a contribution from the Chief Scientist of Quebec , who invites you to follow him on Facebook , Twitter and Instagram .

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