How long can you stand near someone before possibly getting exposed to COVID-19?

cdc close contact definition changed
Photo via Eelke/Flickr (CC BY 2.0)

Americans have heard the term social distancing and the recommendation to stay six feet away from people for months now. Those recommendations can help people to mitigate their risk of contracting coronavirus. Of course, the pandemic is still continuing — evinced by the news on Oct. 22 that the U.S. set a new record for daily coronavirus cases, with 77,640 new cases reported. Earlier that week, the Centers for Disease Control and Prevention adjusted its definition of what close contact means, expanding the guidelines for what constitutes risk.

While being within six feet of an infected person is still seen as a key risk factor, the CDC has now revised the time of exposure in its “close contact” guidelines. Previously, the threshold was 15 minutes of exposure to an infected person within six feet. The CDC has now revised that to 15 minutes of exposure within a 24-hour period, including multiple brief encounters that add up to 15 minutes. The CDC also recently changed its stance regarding whether the virus can spread via airborne particles.

According to STAT News, the revised guideline for close contact coincides with a study involving a Vermont correctional officer who contracted the coronavirus in August. The CDC Mortality and Morbidity Weekly Report article details the case of a 20-year-old male who “had multiple brief encounters with six incarcerated or detained persons while their SARS-CoV-2 test results were pending.”

“Experts have long noted that the 15-minute, within-six-feet rule was not some sort of threshold that needed to be hit for transmission to occur,” according to STAT. “So much about whether spread happens depends on how infectious a person is, how well ventilated the room that people are in is, how the virus might move through the air in a particular setting, whether people are wearing masks, and more. The 15-minute window had just been used as a benchmark to prioritize who should be followed up with for contact tracing and quarantine.”

Still, the 15-minute guideline has led to some curious practices implemented in the interest of public health. The New York Times revealed that Billings Public Schools, the largest school district in Montana, called for students to move every 15 minutes to conform to the CDC close contact parameters.

Greg Upham, the superintendent of the 16,500-student school district, was looking to alleviate the burden that contact tracing had become. Billings designed its policy to encourage school employees to be cognizant of the 15-minute window. However, as the article observed, encouraging students to shuffle places within the classroom could actually increase the risk of each student’s infection and could complicate contact tracing.

Sources: CDC, CDC Mortality and Morbidity Weekly Report, NBC News, New York Times, STAT News

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