Small airborne particles may cause large coronavirus problems

In the University of Maryland lab, people infected with the new coronavirus in turn sit in chairs, with their faces on the large ends of a large cone. They recite the alphabet and sing, or sit quietly for 30 minutes. Sometimes I cough.

The cone sucks everything that comes out of the mouth and nose. This is part of a device called “Gesundheit II” that helps scientists study big problems. How does the virus that causes COVID-19 spread from one person to another?

Obviously hitchhiking small liquid particles sprayed by an infected person. People cough, sneeze, sing, scream, talk, and even breathe to expel particles. However, water droplets come in different sizes, and scientists are trying to identify different types of dangers.

The answer affects what we all need to do to avoid getting sick. As a result, the US health agency appeared to have changed its position on the issue a few days ago, but was later reported to have mistakenly announced a new language.

The recommendation to keep at least 6 feet (2 meters) apart (some authorities cite about half that distance) is based on the idea that large particles fall to the ground before moving far. .. They are like drops of window-cleaning splits that can infect someone by implanting or inhaling into the nose, mouth, or eyes.

However, some scientists are now focusing on finer particles, particles that spread like cigarette smoke. They carry air dust and even upward drafts caused by the warmth of our bodies. They remain in the air for minutes to hours, spread throughout the room and accumulate if poorly ventilated.

The potential risk arises from inhaling them. Measles can spread this way, but the new coronavirus is much less contagious.

For these particles, called aerosols, “6 feet isn’t a magical distance,” says Lindseyer, a leading researcher at Virginia Tech’s Blacksburg. However, she says it is still important to stay away from others because aerosols are most concentrated near the source and pose a great risk at close range.

The Public Health Service has generally focused on the larger particles of coronavirus. As a result, more than 200 other scientists Petition In July, we will pay attention to the potential risks of aerosols. The World Health Organization, which has long dismissed the hazards of aerosols, except for certain medical procedures later. Said It aerosol Coronavirus infection cannot be ruled out in the case of infection in a dense, poorly ventilated indoor space.

The issue came to the fore when the US Centers for Disease Control and Prevention recently posted a statement on its website highlighting the concept of aerosol spread and removed it. Authorities said the post was incorrect and the statement was only a draft change to the proposal.

Dr. Jay Butler, Deputy Director of Infectious Diseases at the CDC, told The Associated Press that he continued to believe that the larger and heavier droplets from coughing and sneezing were the primary means of infection.

Butler told a scientific conference last month that current research suggests a possible aerosol spread of the coronavirus, but it does not appear to be the main way people get infected. Further research may change that conclusion, he added, and he added that how often coronavirus aerosol spreads occur, what situations make it more likely, and what appropriate procedures make it. Encouraged scientists to study what might prevent the virus.

Ma said he believes aerosol infections are “much more common than people initially thought.”

As an important part of the evidence, Ma et al. Point out the so-called “superspreader” event, in which one infected person infects many others with the virus in one setting.

For example, in March, 52 people were sitting throughout the room after a member of the Coronavirus Symptoms Choir attended a rehearsal in Washington. found Two people died after being infected. Virus revealed in a crowded and poorly ventilated restaurant in China in January Expansion A pattern from regular customers at lunch to five at two adjacent tables suggests that the aerosol was diffused by the air conditioner. Also in January, Chinese bus passengers apparently Infected Other 23 people. Many were scattered around the vehicle.

Butler said such an event has raised concerns about the spread of aerosols, but has not proven that it will happen.

There may be another way for small particles to spread. William Ristenpart of the University of California, Davis says they may not necessarily come directly from someone’s mouth or nose. his the study It was found that when the flu virus was inoculated into paper tissue and crumpled, particles carrying the virus were released. Therefore, anyone who uses COVID-19 to empty the Recycle Bin with a tissue discarded by someone must wear a mask.

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

Wearing a mask is still important and make sure it fits snugly. Please wash your hands diligently. Again, distance is better than shortening. Avoid congestion, especially indoors.

The main addition to the recommendations is ventilation to avoid increased aerosol concentrations. That’s why researchers keep away from poorly ventilated rooms. Open windows and doors. You can also use an air purifier or virus inactivated UV light.

Best of all: Do as much as you can outdoors. Ultraviolet rays Work in your favor.

“It’s clear that the outdoors are the most effective means. It’s not impossible, but difficult, to get infected outdoors,” said Jose-Luis Jimenez of the University of Colorado at Boulder.

Researchers say that different precautions need to be used in combination rather than individually. In a well-ventilated environment, “6 feet (separation) is pretty good if everyone is wearing a mask,” said Dr. Donald Milton of the University of Maryland’s School of Public Health, a long time directly downwind of an infected person. I will not stay. , The laboratory houses a Gesundheit II machine.

Experts say the risk from a short elevator ride while masked or passing a jogger on the sidewalk is probably less because exposure time is important.

Scientists Release online tool To calculate the risk of airborne diffusion in different situations.

However, at a recent conference on aerosols, Dr. George Benjamin, Executive Secretary of the American Public Health Association, pointed out that preventative measures can be a challenge in the real world. In a home with multiple generations, it can be difficult to stay away from others. He said some old buildings had windows that were “closed a few years ago.” And, “We have too many communities who don’t have access to clean water to wash their hands.”

The details of how it spreads for all scientific frenzy to study the new coronavirus may still be suspicious after nine months. But history suggests patience.

“We have been studying influenza for 102 years,” Milton said, referring to the 1918 influenza epidemic. “We still don’t know how that is communicated and what the role of aerosols is.”

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