A CAF press release said Ahmad, who had been in Morocco for the Confederation Cup final on Sunday, had arrived in Cairo on Wednesday and started to present mild flu symptoms. He underwent a test on Thursday which came back positive on Friday.
World football body FIFA said on Thursday that it had lifted a ban imposed on Sudan last week for government interference in the sport.
After Charles Aranguiz injured himself against Australia, Chile coach Juan Antonio Pizzi is hopeful that the midfielder will be fit for semi-final against Cristiano Ronaldo's Portugal.
Confederations Cup 2017: Hosts Russia take on New Zealand as team's clash for the first time since 1982
Hosts Russia kick off the Confederations Cup against New Zealand in Saint Petersburg on Saturday, targeting victory in their opening match to set the tone for a successful tournament.
The action took place around the beginning of the soccer game between Argentina and Bosnia-Herzegovina — the first World Cup match played in Maracana stadium since 1950.