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Small airborne particles can cause a major problem with the coronavirus



NEW YORK (AP) – In a laboratory at the University of Maryland, people infected with the new coronavirus take turns sitting in a chair and putting their faces at the large end of a large cone. They recite the alphabet and sing or just sit quietly for half an hour. Sometimes they cough.

The cone sucks up anything that comes out of their mouths and noses. This is part of a device called Gesundheit II, which helps scientists investigate a big question: How does the virus that causes COVID-19 spread from one person to another?

Apparently he was hitchhiking on small liquid particles sprayed by an infected person. People emit particles as they cough, sneeze, sing, shout, talk and even breathe. But the drops are available in a wide range of sizes, and scientists are trying to determine how risky the different species are.

The answer concerns what we should all do to not get sick. That̵

7;s why he had made headlines a few days ago when a U.S. health agency seemed to change its position on the issue, but later said had published a new language by mistake.

The recommendation to stay at least 2 meters away – some authorities cite about half that distance – is based on the idea that larger particles fall to the ground before they can travel very far. They are like drops in a syringe of window cleaner and can infect someone by landing on their nose, mouth or eyes or they can be inhaled.

But now some scientists are focusing on smaller particles, those that spread more like cigarette smoke. They are carried by air currents and even upstream currents caused by the heat of our bodies. They can stay in the air from minutes to hours, spread in a room and accumulate if ventilation is poor.

The potential risk comes from inhaling them. Measles can spread this way, but the new coronavirus is far less contagious than that.

For these particles, called aerosols, “6 feet is not a magic distance,” said Lincy Marr, a lead researcher who studied them at Virginia Tech in Blacksburg. But she says it’s still important to stay away from others, “the farther away, the better,” because aerosols are most concentrated near a source and pose a greater risk at close range.

Public health agencies typically focus on larger coronavirus particles. This prompted more than 200 other scientists to publish an application in July to address the potential risk of aerosols. The World Health Organization, which has long ruled out the dangers of aerosols, with the exception of some medical procedures, said later that aerosol transmission of the coronavirus cannot be ruled out in cases of infection in crowded and poorly ventilated internal spaces.

The issue came to light recently when the US Centers for Disease Control and Prevention published and deleted statements on its website that highlighted the idea of ​​aerosol proliferation. The agency said the publication was a mistake and that the statements were simply a draft of proposed changes to its recommendations.

Dr. Jay Butler, CDC’s deputy director of infectious diseases, told the Associated Press that the agency continues to believe that larger and heavier droplets that come from coughing or sneezing are the main means of transmission.

Butler said at a scientific meeting last month that current research shows that the spread of coronavirus in aerosols is possible, but it doesn’t seem to be the main way for people to become infected. Further research could change that conclusion, he added, and called on scientists to study how often the coronavirus spreads in an aerosol, what situations make it more likely, and what reasonable steps can prevent it.

Marr said she said “aerosol contamination is happening much more than people were initially inclined to think.”

As key evidence, Marr and others cite so-called “over-spread” events, in which one infected person apparently transmitted the virus to many others in one setting.

In March, for example, after a member of a choir with coronavirus symptoms attended a rehearsal in Washington state, 52 others were found sitting across the room. to be infected and two died. In a crowded and poorly ventilated restaurant in China in January, the virus apparently spread from a patron at noon to five people at two adjacent tables on a model suggesting that aerosols are spread by air conditioning. Also in January, a passenger on a Chinese bus was apparently infected 23 others, many of whom were scattered around the vehicle.

Butler said such events raised concerns about the spread of aerosols, but did not prove that they were happening.

There may be another way to propagate small particles. They don’t have to come directly from someone’s mouth or nose, says William Ristenpart of the University of California, Davis. His research found that if paper tissues were inoculated with influenza virus and then crushed, they released particles that carried the virus. So people emptying a trash can with tissue discarded by someone with COVID-19 should make sure they wear a mask, he said.

Scientists who warn of aerosols say the current recommendations still make sense.

Wearing a mask is still important and make sure it fits snugly. Continue to wash these hands thoroughly. Again, staying away from each other is better than staying closer to each other. Avoid crowds, especially indoors.

Their main addition to the recommendations is ventilation to avoid the accumulation of aerosol concentrations. So, researchers say, stay away from poorly ventilated rooms. Open windows and doors. Air purifiers or virus inactivating ultraviolet light may also be used.

Best of all: Just do as much as you can outdoors, where the dilution and ultraviolet light of the sun work in your favor.

“We know it’s openly the most remarkably effective measure ever,” said Jose-Luis Jimenez of the University of Colorado-Boulder. “It’s not impossible to get infected outdoors, but it’s hard.”

The various precautions should be used in combination, not just one at a time, the researchers said. In a well-ventilated environment, “6 feet (apart) is pretty good if everyone has a mask,” and no one is left directly winded by an infected person for a very long time, says Dr. Donald Milton of the University of Maryland School of Public Health. in whose laboratory the Gesundheit II machine is housed.

The length of exposure is important, so there’s probably no high risk of a short elevator ride while you’re masked or jogging on the sidewalk, experts say.

Scientists have published online tools to calculate the risk of airborne spread in different settings.

At a recent aerosol meeting, however, Dr. George Benjamin, executive director of the American Public Health Association, noted that preventive steps can be a challenge in the real world. Moving away from other people can be difficult in homes that house several generations. Some old buildings have windows that were “nailed down years ago,” he said. And “we have too many communities where they just don’t have access to clean water to wash their hands.”

It may seem strange that for all the scientific madness of studying the new coronavirus, the details of its spread may still be in doubt nine months later. But history requires patience.

“We’ve been studying the flu for 102 years,” Milton said, referring to the 1918 flu epidemic. “We still don’t know how it is transmitted and what the role of aerosols is.”

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The Associated Press’s Department of Health and Science receives support from the Department of Scientific Education at the Howard Hughes Medical Institute. The AP is solely responsible for all content


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