UPDATE: Per an NFL spokesperson, Hairston is not eligible to return this season, since he suffered the illness after the start of training camp.
The 6-foot-6, 330-pound Hairston had been on the active/physically unable to perform list since the start of training camp. General manager Doug Whaley said at the time that Hairston was dealing with a back injury.
A fourth-round pick of the Bills in 2011, Hairston has started 15 games over the past two seasons.
Veteran Erik Pears has started in place of Hairston at right tackle this preseason.