The CDC just changed it's definition of "close contact", from 15 consecutive minutes closer than 6 feet away from an infected person, to a total of 15 minutes within a 24-hour period. The reason they did this is that an employee at a correctional facility contracted the virus from an asymptomatic inmate who he (or she) only had incidental contact with. Both were wearing masks during this incidental contact.

Link:

https://www.statnews.com/2020/10/21/cumulative-time-covid-19-spread/