Areport from the National Academy of Science, Engineering and Medicine to the White House Office of Science and Technology Policy released on April 1 states that based on current research, SARS-CoV-2 may be spread through aerosols. The letter cites a recent study at the University of Nebraska Medical Center that found “widespread evidence of viral RNA in isolation rooms where patients with SARS-CoV-2 were receiving care” in air and surface samples. Even air collectors that were more than six feet away from patients detected the RNA, calling into question whether current social distancing guidelines are sufficient to prevent the spread of the disease.
To date, the Centers for Disease Control and Prevention (CDC) has stated that larger respiratory droplets expelled when infected people cough or sneeze are the primary means of transmitting the coronavirus, reports Science, but the possibility that SARS-CoV-2 could be airborne implies that recommendations about mask wearing in public may need to be revised.
“In the mind of scientists working on this, there’s absolutely no doubt that the virus spreads in the air,” aerosol scientist Lidia Morawska of the Queensland University of Technology in Australia tells Nature. “This is a no-brainer.”
A study from the University of Hong Kong that has not yet been peer-reviewed detected rhinovirus, influenza, and human coronaviruses (not including SARS-CoV-2) in respiratory droplets and aerosols, and found that surgical masks worn by sick patients reduced the detection of coronavirus RNA in both transmission forms, according to the NASEM report. Another preprint conducted in two Wuhan, China, hospitals indicates that staff movement, floor cleaning, and the removal of personal protective equipment could transmit the virus through the re-suspension of virus-contaminated aerosols.
“[I’m] relieved to see aerosolization is accepted,” says Kimberly Prather, an aerosol chemist at the University of California, San Diego, in remarks to Science. “This added airborne pathway helps explain why it is spreading so fast.”
Virologist Leo Poon of the University of Hong Kong tells Nature that evidence for the airborne transmission of SARS-CoV-2 isn’t yet sufficient, and Nature reports that a study from an outbreak center in Singapore found no evidence of the virus in air samples.
The World Health Organization (WHO) states that airborne transmission may be possible during certain medical procedures such as intubation or open suctioning, but cautions that a recent study published in the New England Journal of Medicine that used a high-powered nebulizer to generate aerosols is not the same as real-life situations of people coughing. “Further studies are needed to determine whether it is possible to detect COVID-19 virus in air samples from patient rooms where no procedures or support treatments that generate aerosols are ongoing.”
Michael Osterholm, an infectious disease epidemiologist at the University of Minnesota, tells Nature that definitive research on the airborne transmission of SARS-CoV-2 may take years, and that we shouldn’t “let perfect be the enemy of convincing.”
Despite the uncertainty regarding the transmission of the coronavirus, public policy appears to be shifting. Los Angeles mayor Eric Garcetti tweeted today that residents should wear face coverings made of bandanas, scarves, or other fabric, and Science reports that the CDC may be preparing to recommend that all people in the United States wear cloth facemasks in public.