Part of the reason the coronavirus is so frightening is its invisibility. We can’t see where the virus lingers and have no idea if we’re coming into contact with it. But early on in the pandemic, many stressed that we didn’t need to focus on airborne transmission ― but is that still the case?
Data over the last few months now suggests it is not, although there are still conflicting stances. Since July, hundreds of public health experts from around the world have been urging officials to take airborne spread more seriously. The World Health Organization has previously said it has been monitoring evidence of COVID-19 airborne transmission. It’s suspected that these particles can remain in the air for up to three hours.
The Centers for Disease Control and Prevention officially updated its coronavirus guidance in mid-September to warn the disease may spread through airborne particles. However, that guidance was removed days later because “that does not reflect our current state of knowledge,” a top CDC official told the Washington Post.
Before it was removed, the CDC’s page on transmission said there “is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants, or in fitness classes).”
A study published in the New England Journal of Medicine examined airborne transmission back in April. Researchers looked at how long the virus lasted on surfaces like steel and plastic, as well as how long the virus stayed in the air in the form of an “aerosolized particle.”
Aerosolized particles are essentially microscopic, and they’re formed when fluids containing the virus are expelled from a person and cling to dust or moisture in the air and hang there. The researchers found that airborne coronavirus particles stayed floating for up to three hours before falling and clinging to a new surface.
The NEJM study came with some major caveats, like the fact that it was conducted in a very controlled setting. Immediately after the study’s publication, experts said that airborne transmission was mostly a concern in healthcare settings, and that the main causes of transmission were contact with respiratory droplets from someone who is sick or with a contaminated surface.
Linsey Marr, an expert in virus transmission by aerosol at Virginia Tech in Blacksburg, told the New York Times when the NEJM study came out that you should think of airborne coronavirus transmission like cigarette smoke. Marr, who was not affiliated with the study, said that the closer and sooner you are exposed to the person who exhaled the smoke, the more of a whiff you might get. The exposure decreases the further away you are and the longer the time has passed.
So why all the confusion, and no essential conclusion? Keep in mind that the coronavirus is still relatively new to the medical world. What’s known about COVID-19 has changed since the start of the pandemic and likely will continue to change as time goes on.
How to protect yourself from airborne transmission
You’ve likely already heard it, but it remains true: Social distancing and mask-wearing are incredibly important when you’re out of your house.
Face coverings can offer decent protection against inhaling the virus, according to Harvard Health. And the farther away you are from others, the less likely it is that you’ll come into contact with the virus, whether it’s through direct exposure or aerosolized particles. You never know who could be infected; there have been many asymptomatic cases of COVID-19.
Before the CDC reversed its September guidance, the agency had noted that “in general, indoor environments without good ventilation” can increase your risk of contracting the virus via airborne particles or respiratory droplets.
That’s why it’s important to keep your space well-ventilated. Some evidence suggests air conditioning may play a role in indoor virus transmission. Opening windows and letting in fresh air is a better way to help prevent disease spread.
“Get outdoor air moving,” Joseph Allen, director of the Healthy Buildings program and a professor of exposure assessment science at Harvard’s T.H. Chan School of Public Health, previously told HuffPost. “Open doors and windows as much as possible. Higher ventilation rates can be helpful in reducing the risk of viruses in general.”
Experts have also previously suggested using a humidifier to make your indoor humidity around 40 to 60% as another line of defense. Research published this September suggests dry, indoor environments can contribute to COVID-19 airborne transmission. Humidity may help reduce germs and is more optimal for human health, according to scientists.
The CDC also recommends using air purifiers to help reduce airborne germs and prevent COVID-19 from spreading.
Finally, continue to wash your hands and keep things clean. Spend at least 20 seconds using warm water and soap (it doesn’t matter what kind) and a clean towel or paper towel to dry them off. You can also use sanitizer if you’re unable to use soap and water. Take the time to do it every time you come home, before eating, after using the bathroom and whenever else you think it’s necessary. You should also continue to disinfect high-touch surfaces like doorknobs.
This story has been updated from earlier in the coronavirus pandemic with new information regarding airborne transmission.
Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the World Health Organization or the Centers for Disease Control and Prevention for the most updated recommendations.