How COVID-19 Spreads

We learn more about SARS-CoV2 (the virus) and COVID-19 (the disease) each day. Recently, the CDC has updated public information regarding the modes of transmission (newly admitting to the occasional occurrence aerosol transmission):

COVID-19 most commonly spreads during close contact.
• People who are physically near (within approximately 6 feet) a person with COVID-19 or who have direct contact with that person (handshakes, hugs, and kisses) are at the greatest risk of infection.

• The mechanism of the vast majority of close contact transmission is via respiratory droplets. People produce respiratory droplets when they cough, sneeze, sing, talk, or just breathe. The more forceful the exhale, the more respiratory droplets are likely to be produced and the greater their velocity (which promotes further spread). Infection transmission occurs when a respiratory droplet carrying the virus is inhaled by another person or deposited on another person’s mucous membranes (such as those that line the eyes, nose, and mouth).

• Masks are most effective when worn as source control, meaning that they act as a barrier to prevent the majority of a person’s potentially infectious respiratory droplets from escaping. And keeping a distance of at least 6 feet between yourself and others is critical to the avoidance of droplet transmission. Together, masking and social distancing are proven to be effective at mitigating the risk of transmission of COVID-19.

COVID-19 can occasionally be spread by airborne transmission.
• Most respiratory droplets, owing to gravity, fall from the air quite quickly. Smaller droplets and particles called aerosols, though, can linger in the air for minutes to hours. There is evidence that, under certain conditions, people with COVID-19 seem to have infected others who were more than 6 feet away. In enclosed spaces with poor ventilation, and when an infected person is breathing heavily (singing or exercising, for instance), scientists believe that aerosols may become concentrated enough to allow COVID-19 to transmit over distances greater than 6 feet or even (shortly) after the infected person has left the space.

• Masks worn for source control are the best means of preventing both droplet and aerosol transmission. It is also important to avoid crowded indoor spaces, places where people are prone to heavy breathing, and areas with poor ventilation.

COVID-19 spreads less commonly through contact with contaminated surfaces.
• Respiratory droplets can land of surfaces and objects. It is possible that a person can unwittingly infect themselves with COVID-19 by touching a surface or object that has the virus on it and subsequently touching their own mouth, nose, or eyes. It is thought that this method of transmission is uncommon.

• To prevent this form of transmission, wash your hands often with soap and warm water or use a hand sanitizer containing at least 60% alcohol. Avoid touching your face and routinely clean and disinfect frequently touched surfaces.