Under the new definition, a series of brief encounters can add up. The CDC now considers close contact to mean being within 6 feet of a contagious person for “a cumulative total of 15 minutes or more over a 24-hour period.” Previously, close contact required sustained exposure for at least 15 minutes at one time. An infected person is considered contagious starting 2 days before experiencing symptoms or, for those without symptoms, starting 2 days before collecting a positive test specimen.
The new definition has been added in an appendix that is referenced by many CDC guidance documents, including the CDC’s guidelines for investigating cases and contact tracing. It also now informs the CDC frequently-asked questions on COVID-19.
Why the change?
The change is the result of a new case study, published Wednesday by the CDC, about a case involving a 20-year-old prison guard in Vermont. The guard contracted COVID-19 after intermittent contact with six inmates who were awaiting COVID-19 test results. By studying surveillance camera footage and shift logs from the prison, investigators were able to determine that the guard had multiple, brief encounters of no more than one minute or so each with the inmates.
During his 8-hour shift, the guard was within 6 feet of an infectious inmate approximately 22 times for an estimated total of 17 minutes throughout the day. He wore a cloth mask, gown, goggles, and usually gloves. The inmates wore masks outside their cells but occasionally interacted with the officer in a cell doorway or recreation area without masks. The guard was not known to be exposed to anyone else infected with COVID-19 at work or outside work.
The CDC is honest about the fact that there are limited data about these issues, and says that it is “difficult to precisely define” close contact. The current 15-minute rule-of-thumb is intended to be practical advice for contact tracing. In reality, many other factors can affect whether an exposure actually occurred, including proximity to the COVID patient, duration of exposure, symptoms indicating higher viral shedding, occurrence of aerosol-generating activities (like coughing, singing, or shouting), and environmental conditions (including crowding, ventilation, and indoor vs. outdoor contact).
Is it close contact if people are wearing masks or PPE?
Generally yes, according to the CDC. The agency says that we should consider people to be in close contact regardless of whether they wear masks or respirators. In reality, research has found that masks and PPE can provide significant protection. However, as a practical matter, the CDC does not assume that any particular mask or respirator was adequate or used properly. Masks come in many varieties and most effectively protect the wearer. Likewise, PPE requires appropriate training, selection, and fit-testing to be fully effective.
As a result, the CDC’s guidelines encourage using these protective measures on the one hand to reduce exposures. On the other hand, the guidance suggests erring on the side of caution when establishing social distancing, investigating cases, and tracing contacts by not assuming that any given mask or respirator was effective. Wearing a mask thus does not prevent someone from being considered in “close contact.”
Why does this matter?
The definition of close contact is a key element of most employer, healthcare facility, school, and other institutional plans to prevent the spread of COVID-19. These plans typically require distancing designed to avoid close contact between individuals and require isolation when close contact with a case of COVID-19 occurs.
As a result, the updated definition may cause employers to make and enforce even stricter social distancing rules. If casual interactions totaling 15 minutes throughout the day allow transmission of the virus, some employers may re-think how much they encourage or allow employees to interact in person.
It also means that more people will have to isolate after discovering confirmed cases of COVID-19. Individuals who came in close contact with an infected person are generally expected to isolate for at least 14 days after the last exposure. Broadening the definition of close contact to include even brief interactions could greatly expand the universe of people impacted.
Although the CDC has experienced challenges with a politicized climate and evolving knowledge of the virus, it remains the key source for guidance on preventing the spread of the virus in the United States. Companies and organizations tend to follow CDC guidance both in order to keep people healthy and also in the hopes of avoiding legal liability from OSHA or private plaintiffs (by showing diligent, reasonable efforts to comply with the latest expert guidance).
What should I do?
Here are a few key steps that companies and organizations should consider in light of the new guidance:
- If you don’t yet have a COVID-19 plan, create one!
- Review existing COVID-19 plans and policies, and make appropriate updates, if necessary, to the definition of “close contact.”
- Consider whether social distancing policies should be stricter to prevent employees from having “close contact.”
- Communicate these important changes to team members, and continue to monitor for compliance. Communications may want to take into account that the change could cause some confusion or doubt among some employees or stakeholders. It may help to emphasize in communications that even months after the pandemic began, the response to COVID-19 continues to evolve as experts gather more information and learn more about the virus.
- Ensure that those responsible for implementation use the updated definition in future contact tracing and isolation efforts.