Minnesota Vikings wide receiver Adam Thielen was among several players to be placed on the reserve/COVID-19 list on Monday.
Thielen leads the NFL in receiving touchdowns with 11 but his participation in the Vikings' Week 12 clash with the Carolina Panthers is now in question.
The reserve/COVID-19 designation means a player has either tested positive for coronavirus or has come into close contact with a person who has contracted the virus.
Earlier, the Baltimore Ravens confirmed several members of their organisation had tested positive, leading to them closing their practice facility.
They have since revealed that running backs Mark Ingram and J.K. Dobbins and nose tackle Brandon Williams have returned positive tests.
The Ravens face the 10-0 Pittsburgh Steelers on Thursday in a crucial game for their playoff hopes.
Meanwhile, the Buffalo Bills announced tight end Tommy Sweeney will miss the remainder of the season after being diagnosed with myocarditis.
Myocarditis is an inflammation of the heart and is connected to COVID-19.
The Chicago Bears added safety Eddie Jackson to the reserve/COVID-19 list while the San Francisco 49ers placed that designation on two players.
Defensive linemen D.J. Jones and Jordan Willis have each been added to the list, which now features nine members of the 49ers roster.