来源： 成都电子信息学校 发布时间：2020-07-01 访问量：3313
Mosquito season is upon us, and considering that these bloodsuckers are known to transmit diseases, people are concerned: Do mosquitoes carry the coronavirus? And if so, can they transmit it to humans and infect a person with COVID-19?
Short answer: it's unlikely. Official guidance from the World Health Organization (WHO) says there’s no information or evidence to suggest that the new coronavirus could be transmitted through mosquito bites.
For starters, the coronavirus is a respiratory virus, and the main mode of transmission are viral droplets released into the air when an infected person coughs or sneezes. For a mosquito to become infected with a virus, it must be present in the blood the mosquito feeds on.
"SARS-CoV2 (the virus that causes COVID-19) is a respiratory virus that is almost exclusively contained within the lungs and respiratory tract of infected people, and rarely gets into the blood,” Emily Gallichotte, PhD, a postdoctoral researcher in the department of microbiology, immunology, and pathology at Colorado State University, tells Health.
Plus, for a virus to pass to a person through a mosquito or other kind of insect bite—such as a tick bite—the virus must be able to replicate inside the mosquito or tick. Neither the new coronavirus nor any other type of coronavirus has been shown to do that.
"It’s quite a complex process,” former US Navy entomologist Joseph M. Conlon, who has extensive worldwide experience in mosquito control and is technical advisor to the American Mosquito Control Association (AMCA), tells Health. “First of all, the mosquito would have to pick up the requisite amount of virus during its bite. The virus must then not only survive the digestive process, but replicate within the mosquito and pass through the gut wall to the coelom (main body cavity) of the mosquito. From there it must make its way to the salivary glands and be expressed by the mosquito as part of its salivary secretions.”
Furthermore, mosquitoes are very genetically different from humans. “This makes it challenging for viruses to have the ability to infect both of us,” says Gallichotte. “We have different receptors on the surface of cells and different replication machinery inside our cells.”
Relatively few human viruses have the ability to infect both humans and mosquitoes. “The vast majority of human viruses (such as influenza, HIV, and herpes) have been infecting humans for a very very long time, and even though many of these end up in our blood, they are still unable to infect mosquitoes,” says Gallichotte. “Conversely, there are many mosquito viruses that are unable to infect humans, or any mammals. There are no known coronaviruses that can infect mosquitoes.”
Viruses that can be spread to humans by mosquitoes include West Nile virus, the virus that causes dengue fever, and chikungunya virus, which all circulate in the blood of infected people. “West Nile virus is able to infect a mosquito to the point where the virus load is abundant in the salivary glands,” Melissa Doyle, scientific program manager at the San Gabriel Valley Mosquito and Vector Control District (SGVMVCD), tells Health. “When the mosquito bites a person, the virus is able to travel from the salivary glands into the human body.”
So it’s pretty clear that COVID-19 is the last thing you should be worrying about if a mosquito has been feasting on your leg. Keep swatting them away, though. “Due to the heavy focus on COVID-19, many people may forget that disease threats may already be buzzing right outside their window.” SGVMVCD Public Information Officer Levy Sun tells Health.
Conlon points out that mosquitoes can factor into the severity of COVID-19, meaning it’s crucial to maintain robust measures to reduce their numbers. “Studies have shown that factors contributing to potentially serious or fatal outcomes attendant to COVID-19 infection involve underlying medical issues, such as neurologic conditions that weaken the ability to cough or an already stressed immune system due to concurrent infection by mosquito-borne viruses,” he says.
Mosquitoes or no mosquitoes, it’s still crucial to keep following healthy coronavirus protocol to protect yourself and others from COVID-19. Clean your hands frequently, practice social distancing, stay home if you’re sick, and avoid close contact with anyone who is coughing and sneezing.