https://www.nbcnews.com/health/health-news/cdc-changes-guidance-close-contacts-emphasizes-importance-wearing-mask-n1244147 - Excerpt....

The updated https://www.nbcnews.com/health/health-news/cdc-reverses-again-now-says-covid-19-sometimes-airborne-n1242167 - guidance changes the definition of a "close contact" of a Covid-19 case to a person who has been within 6 feet of an infected person for a total of at least 15 minutes in a day. That includes multiple, but brief, encounters, one or two minutes at a time.

Previously, a close contact was defined as spending 15 consecutive minutes with a Covid-19 patient. Those changes were expected to be updated Wednesday on the CDC's website.

"Cumulative exposures can be as hazardous as 15 sustained continuous minutes of exposure," Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center in Nashville, Tennessee, said.