The team has been hit hard by the flu in the past week, with tight end Anthony Hill being the NFL's first confirmed case of swine flu. Hill has recovered and returned to practice Wednesday.
Safety Eugene Wilson was inactive for Sunday's win against Oakland after becoming so ill he could barely walk. He also returned to practice Wednesday.
Cushing was Houston's first-round draft pick, 15th overall. He leads the team with 33 tackles.
Coach Gary Kubiak said Cushing began feeling ill Tuesday night. He called a trainer and was seen by a doctor, who got him on some medication. Kubiak said Cushing was feeling better Wednesday and was kept home as a precaution to the team.
Kubiak is optimistic the worst of these illnesses are behind his team, which plays at Arizona on Sunday.
"We've obviously got some guys that are having some issues, so we're just trying to stay on top of it and do the smart thing with each one of them," Kubiak said. "It's been an issue here for a few days. It has calmed down. Guys that we've had problems with are back out here today. Hopefully it stops."