Although they suck our blood and can transmit a swarm of pathogens, mosquitoes aren’t flying syringes and they don’t transmit every single virus they pick up. For all the evidence we have at this moment, it seems that the novel coronavirus SARS-CoV-2 isn’t transmitted by mosquitoes.
Female mosquitoes need blood to help develop their eggs, which means they often suck the blood of multiple animals or humans, potentially spreading viruses with every single bite. The pathogens mosquitoes spread by sucking our blood cause hundreds of millions of cases of severe illness and kill hundreds of thousands of people each year. But not all viruses can be spread by mosquitoes — can you even imagine a world where HIV, for instance, is spread by mosquitoes?
In the case of HIV, mosquitoes don’t really spread it because the viral levels in our blood are pretty low. In the case of Ebola (another disease not spread by mosquitoes), the situation is even more striking. Even when scientists injected the virus into mosquitoes, they didn’t become infected. One study collected tens of thousands of insects during an Ebola outbreak but found no virus.
So what happens?
Why some pathogens, and not others
When a mosquito sucks some blood, it sucks a bunch of pathogens along with it. But the mosquito doesn’t necessarily become infected.
In order for the mosquito to spread the infection, it needs to become infected itself first, and in order for this to happen, pathogens need to overcome a series of obstacles.
For starters, the infected blood sucked by the mosquito reaches its gut. Pathogens first need to escape the lining of the mosquito gut and enter its bloodstream. From there, they must fight the mosquito’s own immune system in order for the infection to spread. Then, the pathogens need to reach the mosquito’s saliva glands, and only from there, can they hope to spread to other hosts via the mosquito.
For some pathogens, such as Plasmodium which causes malaria, this has become a way of life — well, viruses aren’t technically alive, but you get the point. These pathogens are entirely dependent on mosquitoes to spread them around, but in order to achieve this, they evolved alongside mosquitoes. It may be straightforward for viruses that have adapted to this process but for others, the virus will perish in the gut or be excreted.
Meanwhile, for all its inherent genetic advantages, SARS-CoV-2 has no connection to mosquitoes. It originated in bats, and might have passed through another host on its way to humans, but if it were adapted to mosquitoes, that would be like winning the genetic lottery twice in a row.
Even so, researchers have analyzed this possibility and found no evidence to support the idea that it could pass through mosquitoes. The WHO says as much on its “coronavirus myths” page, and the CDC has also issued similar guidance.
Simply put, the odds of mosquitoes spreading COVID-19 are nil. Although coronavirus has been found in blood samples from infected people, there’s no evidence it can spread via mosquitoes. Even if a mosquito did pick up blood from an infected patient, it wouldn’t be able to spread it.
The new coronavirus is a respiratory virus, spread primarily through droplets generated by coughs or sneezes, or discharge from the nose or mouth. It can also spread through contaminated surfaces, but blood is not a concern at this point.
Of course, it is not entirely impossible for the virus to gain this ability at some point in the future, but it is extremely unlikely for it to do so in a relevant timeframe. Part of the reason why this is unlikely to happen is that, unfortunately, the virus does a good enough job at spreading on its own.
Nevertheless, there are still plenty of good reasons to avoid getting bitten by mosquitoes.
