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According to the CDC, the coronavirus spreads mainly through breath aerosols

The coronavirus most commonly spreads in the air through droplets or other tiny breath particles that seemingly can remain suspended and inhaled, according to the new guidelines from the Centers for Disease Control and Prevention.

The smaller particles known as aerosols are created when an infected person coughs, sneezes, singing, speaking, or breathing and can be inhaled into a person’s nose, mouth, airways, or lungs without good ventilation, according to the CDC, which increases settings without good ventilation Risk of contagion.

“This is believed to be the main cause of the spread of the virus,”

; the CDC posted on its website. “There is growing evidence that airborne droplets and particles float in the air and can be inhaled by others and cover distances of more than two meters (e.g. during choir practice, in restaurants or in fitness classes).”

Aerosol and coronavirus experts said the change marks a profound shift in understanding the spread of the virus, which has claimed nearly 200,000 lives in the United States. However, the updated two-page explanation contained few new guidance on airborne protection.

The Federal Health Office had previously stated that the coronavirus mainly spreads between people within a radius of about two meters and by direct propulsion from exhaled droplets that land in the noses and mouths of people nearby. The CDC also said – and still says – people can be infected by touching something that has the virus on and then touching their mouth, nose, or eyes, but that touch isn’t the main way it spreads .

Researchers studying transmission of the deadly virus noticed the new instructions on Sunday on the CDC website, tagged as Friday’s update. As with some other updates, the CDC made the fundamental changes to its guidelines without posting any notice.

The CDC did not respond to requests to discuss the update on Sunday.

The instructions on the CDC website state that people should not only wear masks, wash hands and stay “at least three feet away from others”, but also stay at home and isolate themselves when sick and “use air purifiers to reduce the germs in the air in indoor spaces. “Previously, the advice was to maintain a ‘good social distance’ of ‘about six feet’.

The CDC and the World Health Organization have long resisted the idea that the coronavirus could spread further than about two meters through the air, with the WHO initially claiming that airborne transmission occurred only during certain medical procedures. In July, under increasing pressure from researchers, the WHO admitted that the virus could linger in the air indoors and potentially infect people even if they practice social distancing.

Aerosol scientists have increasingly found evidence that the virus can spread through microscopic particles of breath – including “super-spreading” events such as choral practices that involve multiple people being infected. This week, the scientific journal Indoor Air accepted a paper for publication that found that many of the 53 choir singers who fell ill after attending a practice on March 10 in Mount Vernon, Washington, were likely to have COVID-19 through transmission got caught in the air.

Jose-Luis Jimenez, an aerosol scientist at the University of Colorado at Boulder and one of the authors of this report, said in an interview on Sunday that the CDC’s updated guidelines were a big change. Until now, he said, scientists at the agency have told the airborne virus when projectile droplets shoot out of a person’s mouth or nose and directly infect another person.

“They changed it and didn’t tell anyone,” he said.

Donald Milton, professor of environmental health at the University of Maryland and an expert on aerosols, said in an interview on Sunday that the CDC was gradually moving towards the concept of airborne transmission as evidence had accumulated and that the agency was making unannounced changes have made his leadership in the past.

“They have paid attention and moved in response to the research. I’m glad to see that they are moving on and that no one is in the way,” he said.

Without notice, in May, the CDC changed guidelines for reopening places of worship, removing a warning from the previous day that the act of singing could contribute to coronavirus transmission – a move reportedly due to pressure from the White House. In Friday’s updated guide, singing was identified as one of the activities that could produce infectious aerosols.

Jimenez and Milton said it was important to wear masks to reduce the risk of spreading and contagious COVID-19. They said it is important to make sure the face coverings fit properly so that aerosols cannot escape or enter through gaps in the mask around the nose or mouth.

“Aerosols can travel more than three feet, but they are more concentrated the closer you get, so standing as far away as possible reduces the risk,” Milton said. “The reason bars have been such a big problem is that when they get alcohol on board and move close to each other to hear and you can’t have a beer or a shot with a mask on.”

Milton and Shelly Miller, another aerosol researcher at the University of Colorado Boulder, are exploring ways to make singing and playing wind instruments safer through distancing, ventilating, and masking with various materials. The research is funded by national choral and instrumental associations whose members were unable to congregate during the pandemic.

Good ventilation reduces the risk indoors, as does simply opening windows to let air circulate, the researchers said. Ceiling units that use ultraviolet light to kill the virus also show promise, they said.

Milton and Jimenez were among a group of researchers drafting an open letter to the WHO, which was eventually signed by 239 researchers from 32 countries, urging officials to accept the possibility that aerosols may play an important role in spreading the virus . The WHO revised its guidelines after receiving the July 6 letter, stating that airborne transmission had not been definitively proven, but recommended avoiding poorly ventilated, crowded rooms.

The CDC has now taken another important step in recognizing the role of aerosols, Jimenez said.

“The entire field of aerosol science tells them that the understanding of ballistic droplets is out of date and it is really aerosols that are spreading the virus,” he said.

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