Droplets, fomites, aerosols…these terms describing the kinds of particles which can spread virus particles rose to the top of our lexicon last year. Initially we focused on fomites, infectious particles deposited on surfaces, and worried that touching our groceries and mail could spread the coronavirus.
Scientists were convinced that most COVID transmission occurred via droplets, large respiratory particles exhaled in a cough or a sneeze that traveled only a short distance from an infected person, which led to the guidance that staying six feet apart would keep us safe. But worrisome case reports of a single individual passing the virus to a roomful of people, and the mitigating effects of ventilation, began to hint at aerosol transmission, a much more insidious type of spread in which the virus is transmitted through much smaller particles, which travel longer distances and can linger in the air for hours.
Aerosol spread is not only worrisome because it makes a pathogen more contagious, but smaller aerosol particles can be inhaled more deeply into the lungs, potentially causing more severe illness. A new review in Science evaluates the current data on COVID transmission and the advances made over the past year in understanding airflow and aerosol spread, making the bold statement that aerosol transmission is not only the main mechanism for COVID-19 spread, but is likely the primary mode of transmission for the vast majority of respiratory diseases.
Today, our lack of attention to ventilation, air purification and other means to reduce aerosol spread means that we are woefully unprepared for children to return to school—and underscores the need for extensive masking to mitigate transmission. But in the long run, better understanding the mechanisms for preventing airborne transmission could allow us to reduce susceptibility to a host of respiratory diseases. Take complications from asthma, which dropped dramatically during the pandemic—leading researchers to posit that viral infections, rather than environmental triggers, could be the more common cause behind exacerbations.
Harnessing this new knowledge will require further research to quantify the effects of spread and mitigation—and the willingness to invest in preventive measures in schools and other public spaces, yet another domain in which bolstering public health could have a meaningful long-term impact on our lives.