Considerations related to the CDC’s updated definition of close contact

One of the biggest challenges for educational entities this school year has been screening, isolating and excluding students and staff appropriately due to COVID-19. School administrators have worked closely with local public health officials and the health department to trace “close contacts” of infected individuals, which has determined who will quarantine as a result of  COVID exposure. Last week, that process got a bit more complicated, when the Centers for Disease Control and Prevention (CDC) updated its definition of “close contact.” 

Previously, the CDC defined a “close contact” as someone who was within 6 feet of an infected individual for more than 15 minutes. On October 20, 2020, the CDC published an “operational definition” of “close contact” as “someone who was within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period starting from 2 days before illness onset (or, for asymptomatic patients, 2 days prior to test specimen collection) until the time the patient is isolated.” The “cumulative total” of 15 minutes is determined by adding together individual exposures in the 24-hour period, which need not have occurred at one time. The CDC gives the example of “three 5-minute exposures” within a 24-hour period, which total 15 minutes.

Acknowledging the limited data available and the difficulty of coming up with a precise definition, the CDC suggests this working definition for use in contact tracing. The CDC also lists a number of “factors to consider when defining close contact,” including the following:

• Proximity (closer distance likely increases exposure risk)
• Duration of exposure (longer exposure time likely increases exposure risk)
• Whether the infected individual has symptoms (the period around onset of symptoms is associated with the highest levels of viral shedding)
• If the infected person was likely to generate respiratory aerosols (e.g., was coughing, singing, shouting)
• Other environmental factors (crowding, adequacy of ventilation, whether exposure was indoors or outdoors)

According to the CDC, whether the contact was wearing a face mask or other respiratory personal protective equipment should not factor into the analysis.

What does this mean for educational entities? The expanded definition of a “close contact” seems likely to increase the number of persons who are identified as close contacts and therefore required to quarantine. At the same time, in determining close contacts, local public health officials may look at factors other than proximity and duration of exposure and instead may look at proximity and duration on a continuum rather than as absolutes (e.g., not just whether a person was within six feet of an infected individual but whether the proximity was inches away or five and a half feet away). This may mean that the local public health officials will seek more detailed information about contacts among students, employees and staff. 

You may want to consider the proactive steps you can take to address concerns about this change in guidance, such as:

• Communicate with your local public health officials to find out whether they will be adjusting requirements to quarantine and how.
• Ask public health officials whether they will be seeking different information for contact tracing purposes.
• Update notification letters to staff and students to make sure that you are not referencing an outdated definition of “close contact.”
• Evaluate whether you need to make changes to your decision-making procedures on when to change between in-person, hybrid and virtual instruction.

More information about the CDC’s updated definitions can be found here.