A year into the coronavirus disease 2019 (COVID-19) pandemic there remains an urgent need to limit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread and to curb the pandemic in the U.S. through non-pharmaceutical interventions. Clear evidence supports the effectiveness of simple strategies in identifying risks and mitigating the spread of infection, with much of this evidence coming from observational studies. Community risk factors for infection can be identified by comparing recent behaviors and exposures among people who have been infected with those who are not infected using a traditional case-control approach. High-risk environments identified from these investigations need to be clearly communicated to the public to support public health measures and motivate individual behavior change to reduce the risk of infection.

In a study published in JAMA Network, they identify key lessons about community transmission. The importance of wearing masks and the clustering of transmission have been shown with COVID-19, with 20% of infected individuals estimated to cause about 80% of SARS-CoV-2 transmissions. About 50% of transmissions are thought to occur from asymptomatic or pre-symptomatic persons. This presents an important challenge for prevention because it increases the propensity for community spread through diverse high-risk activities involving asymptomatic infected persons who unknowingly spread the virus.

The risk is higher in poorly ventilated, indoor spaces when there is prolonged duration of close contact (within 6 feet of someone for more than 15 minutes over a 24-hour period). Large outbreaks or super-spreader events have generally been characterized by a confluence of these factors such as crowded indoor spaces combined with lack of mask use. A tremendous amount has been learned about SARS-CoV-2 transmission over the past year, and a greater awareness of transmission dynamics, including uneven spread of the virus within communities, can be used to guide targeted interventions and policies.

Stay the course, stay well, mask up, get vaccinated, and stay tuned!