The English captain did not specify the nature of the illness but said he has a full squad to choose from.
“…the guys are fit and available for the game tomorrow. That gives us a little more time to name the squad,” Root said in the pre-match press conference.
“So, everyone in that way is as prepared as they would have liked it for the Test match,” he added.
Root said assistant coach Paul Collingwood was one of two members worse affected by the sickness.
India lead the four-match series 2-1 with the final Test slated to begin here at the Narendra Modi Stadium on Thursday.