Cities and states across the country that are seeking to minimize the spread of COVID face a difficult task. With minimal federal guidance and uncertainty about how the virus is spread, many are left wondering how to best protect their communities. While traditionally the CDC has been the place Americans have gone to find health recommendations, their advice recently has been inconsistent.
What has the CDC said about the spread of COVID?
For months, the CDC claimed that Covid-19 is mainly spread through contact between people who are within 6 feet of each other.
“When people with COVID-19 cough, sneeze, sing, talk, or breathe they produce respiratory droplets. These droplets can range in size from larger droplets (some of which are visible) to smaller droplets,” the CDC noted. “Small droplets can also form particles when they dry very quickly in the airstream.”
The agency cites the following as some of the most common ways to get COVID-19:
- Being around someone “with COVID-19” who might “cough, sneeze, sing, talk, or breathe.”
- Inhaling someone else’s virus through your nose and/or mouth.
- Having “close contact” with a person who is sick with the virus (as you might if you live or work with them).
So, what changed?
On September 18, The CDC updated their site to say that, besides direct contact with large droplets, the virus was also airborne, meaning that it can be transmitted through aerosols that travel well beyond six feet. This new information suggested that indoor ventilation would be key to protecting against the coronavirus.
But that’s not the end of the story. Adding even more confusion to the situation, a few days later, the CDC removed the warning that the virus was airborne, claiming that the information was posted in error.
Does that mean that the virus is not airborne?
No. Despite the CDC’s inconsistencies, many scientists have been warning about the dangers of airborne transmission for months.
In July, 239 scientists published a commentary in Clinical Infectious Diseases calling for the recognition of airborne transmission for COVID-19 based on a series of case reports and lab studies.
Around the same time, the World Health Organization added airborne transmission to their COVID page stating, “Short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out.”
On Monday, October 5, in another reversal, the CDC changed its position to agree with the WHO stating, “There is evidence that under certain conditions, people with COVID-19 seem to have infected others who were more than 6 feet away. These transmissions occurred within enclosed spaces that had inadequate ventilation.”
The WHO and CDC are not alone in their assessment. Many scientists, including University of Maryland virologist Don Milton (who is not affiliated with the CDC) agree. During a press conference shortly after the CDC updated its guidance Dr. Milton said, “The take-home is that it’s traveling through the air, and there is no bright line… You’re not safe beyond six feet. You can’t take your mask off at six feet.”
What evidence are scientists using to determine if COVID is airborne?
There have been multiple cases around the world in which the most likely mode of transmission was long-term exposure to aerosols in a poorly ventilated environment. Angela Rasmussen, a virologist at Columbia’s Mailman School of Public Health, describes it as being similar to adding food coloring to a fish tank versus the ocean. Just a few drops will disperse in both environments, but if you continue adding dye, only the fish tank will eventually shift its hue.
This scenario appears to be how the 33 of the 61 members of the Skagit Valley Chorale in Washington State contracted COVID during choir practice. Experts concluded that the virus likely spread in aerosols produced by singing that remained in the air to infect others.
A similar thing happened in a bus in China, when 24 of 67 worshippers on their way to a Buddhist temple caught the coronavirus. Only one passenger who was sitting near the bus windows or door was infected, making the case that ventilation may offer some protection.
How can we minimize transmission?
While the CDC has finally acknowledged the danger of airborne transmission, it continues to stress that the main mode of transmission is through close, direct contact. The following recommendations on their website were included to minimize transmissions:
- Stay at least 6 feet away from others, whenever possible. This is very important in preventing the spread of COVID-19.
- Cover your mouth and nose with a mask when around others. This helps reduce the risk of spread both by close contact and by airborne transmission.
- Wash your hands often with soap and water. If soap and water are not available, use a hand sanitizer that contains at least 60% alcohol.
- Avoid crowded indoor spaces and ensure indoor spaces are properly ventilated by bringing in outdoor air as much as possible. In general, being outdoors and in spaces with good ventilation reduces the risk of exposure to infectious respiratory droplets.
- Stay home and isolate from others when sick.
- Routinely clean and disinfect frequently touched surfaces.