Over the past few months, there has been controversy over the SARS-CoV-2 method, the virus that caused it, traveling from one infected to another. While official guidelines are often unclear, some aerosol scientists and public health experts have maintained that the virus spreads to aerosols traveling in the air at distances both below and greater than 6 feet plays a more significant role than appreciated.
In July, 239 scientists from 32 countries urged the World Health Organization (WHO) to recognize the possible role of airborne transmission in the spread of SARS-CoV-2.
Three days later, the WHO did so, stating that under certain conditions, “short-range aerosol delivery, particularly in specific indoor locations, such as tight and inadequate ventilation spaces for a long period of time infected people cannot be denied. “
Many scientists rejoiced on social media when it emerged that the CDC agreed, recognizing for the first time in a website update on September 18 that aerosols play an important role in spreading the virus. The update states that COVID-19 can be spread “through respiratory droplets or tiny particles, such as such as those in the aerosol, made when an infected person coughs, sneezes, sings, talk or breathe. These particles can be inhaled through the nose, mouth, airways and lungs and cause infections. This is thought to be the main way the virus is spread. ”
However, the controversy resurfaced when, three days later, the CDC reduced that guide, which was allegedly posted by accident, without proper review.
So far, the CDC website does not recognize that aerosols generally spread over SARS-CoV-2 beyond 6 feet, instead saying: “COVID-19 is spread mainly to people who are in close contact contact (for about 6 feet) over a long period of time. occurs when an infected person coughs, sneezes or talks, and drops from their mouth or nose are released into the air and reach the mouths or nose of people close. Drops can also be inhaled from the lungs. “
The site said respiratory droplets can land on different surfaces, and people can become infected from touching those surfaces and then touching their eyes, nose or mouth. It goes on to say, “Current data do not support long-term SARS-CoV-2 aerosol delivery, as seen in measles or tuberculosis. Short-term inhalation of aerosols is a possibility for COVID-19, like many respiratory pathogens However, it is not easy to distinguish from ‘droplet’ transmission based on epidemiologic patterns.Short distance transmission is a possibility especially in crowded medical wards and inadequate. “
Confusion is surrounded by the use of words like “aerosols” and “droplets” because they are not always defined. And the word “airborne” has a special meaning for infectious disease experts and public health officials because of the question of whether the infection can be easily spread through “airborne transmission.” If SARS-CoV-2 is easily spread by airborne contamination, then strict infection control measures should be used, as is the case with airborne diseases such as measles and tuberculosis. But the CDC told CBS News chief medical correspondent Dr. Jonathan LaPook that although airborne spreads play a role in SARS-CoV-2, the role is not as important as airborne infections such as measles and tuberculosis.
All of this may sound like a scientific discussion deep into the weeds – and it is – but it has great implications as people try to stay safe during the pandemic. Some pieces of advice are clearly obvious: wear a mask, wash your hands, avoid crowds, keep your distance from others, the outside is safer than indoors. But what about the “6 foot” policy for maintaining distance in society? If the virus can travel indoors for distances of more than 6 feet, isn’t it logical to wear a mask indoors whenever you are with people who are not part of your “pod” or “bubble?”
Understanding the basic science behind how SARS-CoV-2 travels in the air should help give us strategies for staying safe. Unfortunately, there are still many open questions. For example, even if aerosols made by an infected person can float in a room, and even if aerosols contain some viable virus, how do we know how important a role of possible mode can be? pandemic transmission?
While we waited for the answers from the ongoing research, Dr. LaPook to the top three scientists to try to clean up the air. Recognizing that science is still not set in stone, they gladly agreed to give us their best advice on how to think about protecting ourselves, based on their current understanding of how it can spread the SARS-CoV-2. Below, atmospheric chemist Kimberly Prather, airborne virus expert Linsey Marr and environmental health professor Donald Milton discuss the best precautions you can take to reduce your risk of infection .
In contrast to the early thinking about the importance of transmission through contact with large respiratory droplets, it appears that one of the main ways humans become infected is by breathing in the virus. This is most common when a person is standing within 6 feet of a person with COVID-19 (with or without symptoms), but it can also occur from more than 6 feet away.
Viruses in small, airborne particles called aerosols can infect humans in both short and long range. Aerosols can be thought of as cigarette smoke. As they are more concentrated near an infected person, they can travel farther than 6 feet, linger, build up in the air and stay contagious for hours. Consequently, to reduce the chance of inhalation of this virus, it is important to take all the following steps:
Inside the house:
Practice physical distance – the farther the better.
Wear a face mask when you are with others, even if you can maintain physical separation. Facial masks not only reduce the amount of virus that comes from infected people, but also reduce the chance of you inhaling the virus.
Improve ventilation by opening windows. Learn how to clean the air effectively with methods such as filtration.
Wear a face mask if you can’t physically get at least 6 feet away or, ideally, more.
Whenever possible, move out group activities.
Whether you are inside or outside, remember that your risk increases with the duration of your exposure to others.
On the question of delivery, it is not only the public who are confused. There has also been confusion among scientists, medical professionals and public health officials, in part because they often use the words “droplet” and “aerosols” differently. To address the confusion, participants in an August workshop on air transmission in SARS-CoV-2 at the National Academies of Science, Engineering, and Medicine agreed on these definitions for respiratory droplets and aerosols:
Drops is larger than 100 microns and will fall to the ground within 6 feet, traveling like tiny cannonballs.
Aerosols is smaller than 100 microns, is highly concentrated near a person, can travel farther than 6 feet and can last and build up in the air, especially in poorly ventilated rooms.
All breathing activities, including breathing, talking and singing, produce more aerosols than droplets. A person is more likely to inhale aerosols than to be sprayed by a droplet, even over short distances. The exact percentage of delivery of droplets versus aerosols can still be determined. But we know from epidemiologic and other data, especially the explosion of events, that the infection occurs by inhalation of aerosols.
In short, how do we get infected with SARS-CoV-2? The answer is: In the air. Once we recognize this, we can use the tools we already have to help end this pandemic.
Kimberly A. Prather, PhD, Distinguished Chair in Atmospheric Chemistry, Scripps Institution of Oceanography, UC San Diego.
Linsey C Marr, PhD, Charles P. Lunsford Professor of Civil and Technical Environment, Virginia Tech.
Donald K Milton, MD, DrPH, Professor of Environmental Health at The University of Maryland School of Public Health.