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‘Close contact’: CDC updates definition for contact tracing

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Washington — The Centers for Disease Control and Prevention has changed part of its criteria for COVID-19 contact tracing, altering its definition of “close contact.”

Updated Oct. 21, “close contact” now means 15 total minutes of exposure to an infected person at a distance of 6 feet or less over a 24-hour period. For example, three five-minute periods within 24 hours meets the new definition. Previously, close contact was considered 15 consecutive minutes of exposure at 6 feet or less in 24 hours.

 

The 24-hour period starts two days before the onset of illness or, for asymptomatic patients, two days before “test specimen collection” and ends when the infected person is isolated.

CDC says other factors to consider when defining close contact include:

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

CDC notes that wearing a face covering or an N95 respirator doesn’t influence the definition of “close contact.”

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