A handful of players were told to stay away from the training ground this week in a bid to contain the problem.
Lewis, United’s caretaker manager, is optimistic it will have passed by the time they face Burton Albion at the Kassam Stadium today.
He said: “There is a bug knocking about, but hopefully that won’t affect anything.
“One or two have had it, there’s no point them coming in and spreading it around.”
Tom Newey will return at left back after a two-game suspension, with Jake Wright likely to revert to his more favoured centre back role.
Burton may be forced into a change at right back, where Phil Edwards (foot) is a doubt.
Oxford Utd: from Clarke, Hunt, Mullins, Wright, Newey, Potter, Wroe, Rose, Williams, Kitson, Constable, Connolly, Smalley, Rigg, Ruffels, Davies, Raynes, Long, Henly.
Burton Albion: from Lainton, Edwards, Sharps, Cansdell-Sherriff, McCrory, Ismail, Weir, Palmer, Phillips, Kee, Alexander, McGurk, Knowles, MacDonald, Bell, Gray, Holness, Lyness.