The 28-year-old was due to return to training this weekend following his exploits for Chile earlier this summer, but the attacker did not report for duty.
Wenger, however, has claimed that Sanchez "has flu", with the 67-year-old moving to deny suggestions that the forward has gone on strike in a bid to force a move away from the club.
"Alexis has flu. I had a text yesterday. He will come back as soon as possible. There is no development [on his future] - he is staying, of course," Wenger told reporters.
It has recently been reported that Man City are prepared to pay Sanchez £320,000 a week in order to convince the former Barcelona attacker to make the move to the Etihad Stadium in this summer's transfer window.