Is COVID-19 Airborne? Scientists Urge WHO to Update Guidelines

As cases of coronavirus (COVID-19) show no signs of stopping, we’ve grown accustomed to precautions—like face masks and social distancing—encouraged by public health organizations such as the World Health Organization (WHO). However, an open letter to WHO signed by 239 scientists in 32 countries argues these precautions are not enough. 

The letter, published on July 6 in Clinical Infectious Disease, appeals “to the medical community and to the relevant national and international bodies" requesting that they "recognize the potential for airborne spread of COVID-19." 

COVID-19 is commonly thought to spread via close contact with an infected person’s respiratory droplets, such as from sneezing, talking, or coughing. But the claims of this open letter intensify a growing debate in the medical community over how the virus is actually spread.

According to the scientists behind the letter, airborne transmission is "the only plausible explanation" for COVID-19 outbreaks that occurred even when people had no close contact with one another.

What Is Airborne Transmission?

"A virus is considered airborne if it can be infectious from an aerosol—a very small respiratory droplet that can linger in the air," Kristin Englund, MD, an infectious disease specialist at the Cleveland Clinic, tells Verywell.

Examples of airborne viruses include tuberculosis, influenza, rhinoviruses (the common cold), and viral meningitis. 

Other Types of Viral Transmission

Since the beginning of the pandemic, WHO has said the virus’s potential for airborne spread was limited to aerosol-generating medical procedures, such as inserting a breathing tube. Therefore, its recommendations for the public have focused on droplet and contact transmission, rather than airborne transmission. 

• Droplet: Droplet transmission is caused by large respiratory droplets produced by coughing, sneezing, or talking. These particles don't stay in the air for very long, and don't cause infection unless they touch your body— your eyes, mouth, or nose, in particular.
• Contact: Contact transmission occurs when you touch a contaminated object and then touch your eyes, nose, or mouth.

Is COVID-19 Airborne?

The medical community isn't entirely sure whether COVID-19 is airborne or not.

"This is a new virus and our knowledge of how it spreads is still evolving," Englund says.

The open letter argues because past studies revealed that other coronaviruses, such as SARS and MERS, could spread through the air, COVID-19 probably behaves similarly.

In addition, the letter says one study in Guangzhou, China—home to some of the earliest COVID-19 cases —found that small, aerosolized droplets of COVID-19 were detected in the air.   

WHO Response

In light of the letter, on July 7, WHO held a press conference, stating "the possibility of airborne transmission in public settings, especially in very specific conditions of crowded, closed, poorly-ventilated settings cannot be ruled out."

Benedetta Allegranzi, MD, WHO's technical lead for infection prevention and control, concluded the emerging evidence is not definitive.

Nevertheless, WHO updated its COVID-19 guidelines two days later, advising people to "avoid crowded places, close-contact settings, and confined and enclosed spaces with poor ventilation."

Is It Safe to Be Indoors?

The possibility of COVID-19 being airborne brings new implications for being indoors.

"[Airborne viruses] can be particularly problematic indoors, where it would be easier to inhale the aerosolized virus," Dr. Englund says. 

For this reason, the scientists behind the open letter advocate for the following measures:

• Adequate ventilation, particularly in public buildings, workplaces, and schools.
• Supplemental ventilation such as a high-efficiency filtration.
• Sufficient crowd control, especially in public buildings. 

Do I Need to Protect Myself Differently?

If you're already following recommendations from the Centers for Disease Control and Prevention (CDC) to protect yourself, you probably don't have to change anything about your behavior. Dr. Englund says studies show the vast majority of people who have gotten sick from COVID-19 contracted the virus from droplet transmission.

"Wearing masks, social distancing, not touching your face, and frequent hand washing is effective for preventing the spread of COVID-19," she says.

In Michigan, these measures have been successful in stalling COVID-19 outbreaks, Frank Rosenblat, DO, an infectious disease specialist with Infectious Diseases of Michigan, P.C., tells Verywell. But he thinks additional precautions would be taken if more research shows the virus is, in fact, airborne.

“If COVID-19 was convincingly shown to be airborne, the concentration of efforts to stop its spread would likely shift from the individual to municipal and industry response," he says. "Personally, I would need much more convincing as to airborne spread being important in cases of COVID-19 to make broad recommendations."

A Word From Verywell's Medical Expert Board

"It can be very confusing and worrisome when different sources are relaying information with different language. The recent statement that the coronavirus may be airborne is one example of information that was discussed earlier on in the pandemic. This information is what contributed to some of the current recommendations for prevention of the spread of the virus, including social distancing and mask-wearing. People should continue to wear masks and maintain safe social distancing, as well as avoid areas in enclosed spaces." — Jenny Sweigard, MD

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.