Lot of talk on message boards now about this, and cbs released this: "A virus is making its way through the team. WR Devery Henderson is one of the victims, and while a virus might not be a big deal, it's also unpredictable and could also keep several players out or limit their availability."
I wouldn't worry too much. If it were a major concern, we all would have heard more about this. Henderson was probably the most recent to contract this....perhaps he's also the only high-profile player that had it?