The team announced earlier in the day test results that came in today from Sunday showed one player tested positive.
Pittsburgh is in the intensive protocol now as they wait to see if there are any more positive cases.
McDonald, 30, is a former second-round pick of the 49ers back in 2013. He was in the final year of his rookie contract when the 49ers signed him to a new five-year, $35 million extension, but he was later traded to the Steelers in exchange for a 2018 fifth-round pick.
In 2020, McDonald has appeared in eight games for the Steelers and caught nine passes for 61 yards receiving and no touchdowns.