The Browns placed Jackson (undisclosed/knee) on the reserve/COVID-19 list Thursday.
Jackson missed Wednesday's practice session with a knee injury, and he'll now be forced to isolate from the team. While it's not clear whether he's tested positive for COVID-19, it appears unlikely that he'll be able to play Sunday against the Bengals. If the 31-year-old is held out, Jordan Elliott will likely take on a starting role for Cleveland.