This year, health experts around the world revised their views about how the coronavirus spreads. Aerosol scientists, virologists and other researchers had determined in 2020 that the virus spreads through the air, but it took until 2021 for prominent public health agencies to acknowledge the fact. The admission could have wide-ranging consequences for everything from public health recommendations and building codes to marching band practices (SN: 8/14/21, p. 24).
For decades, doctors and many researchers have thought that respiratory viruses such as cold and flu viruses spread mainly by people touching surfaces contaminated by mucus droplets and then touching their faces. That’s why, in the early days of the pandemic, disinfectant wipes flew off store shelves.
Surface-to-face transfer is still a probable route of infection for some cold-causing viruses, such as respiratory syncytial virus, or RSV. But it turns out that the coronavirus spreads mainly through fine aerosol particles that may hang in the air for hours, particularly indoors.
People spread such aerosols when coughing or sneezing, but also when talking, singing, shouting and even quietly breathing, allowing infected people to spread the disease even before they know they’re sick. Some evidence suggests that the coronavirus may be evolving to spread more easily through the air (SN: 9/25/21, p. 6).
It took collecting reams of data and more than 200 scientists pushing the World Health Organization and other public health agencies to acknowledge airborne spread of the coronavirus. In April 2021, both the WHO and U.S. Centers for Disease Control and Prevention updated their recommendations to note that airborne spread is a major route of infection (SN Online: 5/18/21).
That recognition was vital to public understanding of why wearing well-fitting masks is necessary in public indoor places (SN: 3/13/21, p. 14; SN Online: 7/27/21). Masking, social distancing and other measures to guard against the coronavirus are also credited with nearly wiping out flu last winter (SN Online: 2/2/21). Experts fear a resurgence of cold and flu this winter if those measures aren’t continued (SN Online: 8/12/21).
Knowledge that COVID-19 is an airborne disease has led to such measures as rearranging seating in orchestras (SN Online: 6/23/21) and updating recommendations for proper ventilation and filtration in buildings. Some scientists and activists have also suggested that the safety of indoor air should be regulated to reduce the spread of diseases, much like safety standards for food and drinking water.