We want to alert you to a significant COVID-19 development out of the CDC yesterday. Specifically, the CDC just announced a material revision to its definition of “Close Contact.” The new definition makes it explicit that the 15-minute exposure period (i.e., within 6-feet of an infected individual for 15 minutes) should be assessed based on a cumulative amount of time over 24 hours, not just a single, continuous 15-minute interaction.
Here is the new definition included on the CDC’s website:
Close Contact – 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.
* Individual exposures added together over a 24-hour period (e.g., three 5-minute exposures for a total of 15 minutes). Data are limited, making it difficult to precisely define “close contact;” however, 15 cumulative minutes of exposure at a distance of 6 feet or less can be used as an operational definition for contact investigation. Factors to consider when defining close contact include proximity (closer distance likely increases exposure risk), the 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), and other environmental factors (crowding, adequacy of ventilation, whether exposure was indoors or outdoors). Because the general public has not received training on proper selection and use of respiratory PPE, such as an N95, the determination of close contact should generally be made irrespective of whether the contact was wearing respiratory PPE. At this time, differential determination of close contact for those using fabric face coverings is not recommended.
CDC’s revised view of what constitutes a Close Contact is based on an exposure study at a correctional facility. Here is the CDC’s public notice about the correctional facility analysis. The analysis apparently revealed that virus was spread to a 20-year-old prison employee who interacted with individuals who later tested positive for the virus, after 22 interactions that took place over 17 minutes during an eight-hour shift.
An important consequence of this revision is the impact it will have on employers’ ability to maintain staffing because it establishes a much lower threshold trigger for required quarantine. Recall that
the CDC and OSHA recommend that an employee quarantine for 14 days if s/he experiences a Close Contact exposure with someone who later is determined to have been COVID positive at the time of the contact. The new Close Contact definition will require an employer to tally numerous short-duration contacts over the course of a full work shift (or even over two work shifts spanning a 24-hour period), potentially resulting in many more Close Contacts that will require quarantine.
NOTE: This CDC development does not change anything that is triggered to happen after you identify the existence of a Close Contact exposure, it just changes how you identify circumstances that constitute a Close Contact. So it still remains the case that essential workers/critical infrastructure workers who experience a close contact exposure but who remain asymptomatic, may continue to work with a face covering, symptom screening, and other safe work practices.
A few states had already deviated from the 15-minute trigger. For example, Colorado has been operating under this interpretation (the 15-minute trigger is a cumulative period) for months, and New Mexico also has established an extremely short duration trigger for a Close Contact. However, until today, on the federal level, the CDC expressly recognized that brief interactions were unlikely to result in transmission, so many employers have operated on the assumption that multiple brief exposures were similarly unlikely to result in transmission. CDC’s new definition rejects that view.
We are frequently asked whether it matters if either or both individual(s) involved were wearing masks. CDC’s guidance has been consistent on that point. That is, the use of face coverings does not impact the determination of a Close Contact (even, it seems, if the face covering is a proper respirator like an N95). According to the CDC’s Public Health Guidance for Community-Related Exposure (FN 2):
“the determination of close contact should be made irrespective of whether the person with COVID-19 or the contact was wearing a mask. Because the general public has not received training on proper selection and use of respiratory PPE, it cannot be certain whether respiratory PPE worn during contact with an individual with COVID-19 infection protected them from exposure. Therefore, as a conservative approach, the determination of close contact should generally be made irrespective of whether the contact was wearing respiratory PPE, which is recommended for health care personnel and other trained users, or a mask recommended for the general public.”
In the circumstances just studied by the CDC in connection with its new definition of Close Contact, the prisoners with whom the guard had several brief interactions wore cloth masks during most of the interactions but not always, but the correctional officer always wore a cloth mask, gown, and eye protection.
That is not to say that employers may never consider use of respiratory protection in identifying close contacts. In our view, the CDC is drawing a distinction between those work environments where N95s are being used outside the context of a comprehensive respiratory protection program, and typically on a voluntary-use basis. Healthcare and other sophisticated employers that do have comprehensive respiratory protection programs, complete with fit testing and training, can rely on N95s to avoid having to treat close interactions as “close contacts.”
As a result of this new Close Contact definition, employers should review their COVID-19 infection control plans with this new definition in mind and, at minimum, update their contact tracing questionnaires to include inquiries focused on the cumulative approach, such as:
ID individuals with whom you had close contact within 48 hours of illness onset or sample collection.
Were you in close contact with anyone for 15 minutes or more in a single encounter in that period?
Did you have multiple shorter close contacts with anyone during any 24-hour span over that period (if so, how long total were you in close contact with each such person)?
Contact us if you have any questions about this development.
Last Updated October 22, 2020
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