Sanchez was set to report back for pre-season on Sunday after his summer break, but has stayed away because of illness.
"He has flu, yes. I had him on text yesterday," said Wenger after Saturday's 5-2 win over Benfica.
"There's no development - he is staying, of course."
The striker posted a picture on Instagram on Friday with the one word caption 'sick.' He had been given permission to return to pre-season training late after helping Chile to the Confederations Cup final in Russia.
Sanchez, 28, is entering the final year of his Arsenal contract, as are Mesut Ozil, Kieran Gibbs, Alex Oxlade-Chamberlain and Jack Wilshere.
But Wenger, who signed a new two-year deal of his own in May,does not believe that uncertainty over their futures will have a negative impact on the squad.
"The players who have one year of their contract have to respect their contract and play out their contract," Wenger said.
"For a manager, it's a bit different because it concerns more what is the future of the club.
"The players were thinking, 'What's going on and what's happening?', so it creates uncertainty [with my contract] because it's a global policy.
"I am responsible for the global policy of the club but for the players it is different."
Arsenal impressed as they beat Benfica, with Theo Walcott scoring twice and Olivier Giroud and Alex Iwobi also on target while Lisandro Lopez scored an own goal.