The 22-year-old has been a regular for the Red Devils this season, making 10 appearances in all competitions, scoring once and providing one assist in the process.
Amad was named in the Ivory Coast squad for their Africa Cup of Nations qualifying double header against Sierra Leone, with the fixtures due to take place on October 11 and October 15 respectively.
However, it has been confirmed that he has withdrawn from the squad due to illness.
"Amad has withdrawn from the Ivory Coast squad due to illness... the United winger will now return to Manchester, where the Reds host Brentford in our next Premier League outing," read a statement on the club's official website.
Amad withdraws from Ivory Coast squad
Earlier this week, it was revealed that Argentina's Alejandro Garnacho, England's Kobbie Mainoo and Morocco's Noussair Mazraoui had also withdrawn from their national team squads.
Garnacho and Mainoo are both expected to be available against Brentford after the international break, but a check on Mazraoui will be required due to the issue which he suffered against Aston Villa last time out.
There are still a number of Man United players set to represent their countries during the current break, though, with 11 members of the first team currently away on international duty.
Which Man United players are involved in the October internationals?
Victor Lindelof (Sweden), Altay Bayindir (Turkey), Matthijs de Ligt (Netherlands), Joshua Zirkzee (Netherlands), Christian Eriksen (Denmark), Rasmus Hojlund (Denmark), Diogo Dalot (Portugal), Bruno Fernandes (Portugal), Lisandro Martinez (Argentina), Manuel Ugarte (Uruguay) and Andre Onana (Cameroon) are away with their countries.
Harry Maguire was not named in the England squad for their Nations League fixtures with Greece and Finland, although he would not have featured regardless, with the centre-back facing a spell on the sidelines with the muscular problem that he suffered in the goalless draw with Villa on Sunday afternoon.