Four Steps to Fewer COVID-19 Outbreaks | Step 4: Cohorting: Shrink the High-Risk Circle

In this short series, we cover four key strategies that will help reduce the likelihood of a COVID-19 outbreak in your organization.

Liz Ruark
Boy and girl in school

As of September 20, 2022, this post will no longer be updated.

August 2022: Current CDC guidelines no longer recommend cohorting.

In our previous posts in this series, we talked about vaccination, masking, and contact tracing, three of our four primary strategies for decreasing COVID-19 outbreaks in schools and workplaces. In this post, we’ll cover the fourth strategy, which is often neglected these days: cohorting.

Cohorting typically refers to separating an organization into smaller groups of people and ensuring that the groups do not interact with one another. For example, many schools that used hybrid learning models during the 2020-21 school year divided their student body into two cohorts: One cohort of students would come to school during certain times – specified days of the week, or on alternating weeks – while the other cohort learned remotely. Then the two would switch.

For the purposes of the WhenToTest Workplace Testing Planner, however, there’s only one kind of cohort that matters: An unmasked cohort.

An unmasked cohort is group of people who spend chunks of time together indoors without wearing masks under one or both of the following conditions:

  • Close to one another (for example, while eating and/or drinking).

  • While participating in activities that make them breathe heavily or with force (for example, sports, singing, or playing wind instruments).

Why do we care about these two situations? Because being unmasked in either situation puts you at very high risk of getting COVID-19 or giving it to someone else.

Theoretically, the simplest way for workplaces and schools to avoid the risk that unmasked cohorts create is to require that masks must be worn whenever people are indoors together. However, workers and students have to eat lunch. Employees need coffee or water breaks. Little kids need snack time. And not every facility or climate allows for breaks and meals outdoors.

So what’s the next best thing? Make your unmasked cohorts as small as you can. That way, should one member of a cohort come to school or work infected, the number of people they’re most likely to give the disease to is low. (One example of a small unmasked cohort would be a group of four employees who always eat together at a cafeteria table, in a room where the tables are spaced six or more feet apart.)

Cohorting may not be the first thing you think of when you consider your organization’s COVID-19 mitigation strategy, but it’s worth remembering. Paying attention to the number of people who spend unmasked time together can pay significant dividends in COVID-19 prevention.