The Centers for Disease Control and Prevention (CDC) revised its definition of “close contact” to an individual infected with the coronavirus on Wednesday to include multiple, brief exposures adding up to over 15 minutes within 24 hours.
The agency previously said close contact consisted of being within six feet of an infectious person for 15 minutes straight.
The change may prompt health departments to do contact tracing in cases where an exposure might previously have been considered too brief, Dr. William Schaffner, a Vanderbilt University infectious diseases expert, told the Associated Press.
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The revised guideline stems from a CDC report released Wednesday on a 20-year-old male correctional officer in Vermont who had several brief encounters with six inmates who later tested positive for COVID-19.
This event happened in late July to mid-August, and the CDC did not name the correctional facility.
The officer was repeatedly within six feet of infected inmates for about one minute at a time, which ultimately added up to 17 minutes of exposure, according to an investigation that involved video footage.
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While inmates wore cloth masks most of the time, they didn’t wear masks in the recreation room, or during a few brief encounters in cell doorways. The officer wore protective gear but came down with coronavirus symptoms a week later.
The CDC update now defines 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.”
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It marks the second coronavirus-related update that the agency has made in recent weeks, with the first addressing airborne transmission. On Oct. 5, the agency revised its coronavirus guidance to acknowledge the potential for infection through virus-laden particles lingering in the air in enclosed areas with poor ventilation. The revision came two weeks after the CDC issued a correction on its website, saying a draft of proposed changes, including guidance on airborne transmission of coronavirus, was posted in error.
The Associated Press contributed to this report.