Sesko, 22, has been out of action for the past month after picking up a knee injury in Man United’s 2-2 Premier League draw with Tottenham.
The striker was expected to return for their game against Bournemouth on Monday, but Amorim has since confirmed he will miss it due to food poisoning.
Speaking to reporters, Amorim said: "(Harry) Maguire is out, (Matthijs) De Ligt is out, Ben (Sesko) we have to see. We have to see if he's available, he has some food poisoning but let's wait, we have two training sessions still."
Amorim will be hoping Sesko is back as soon as possible with Bryan Mbeumo and Amad Diallo set to leave for AFCON.
United have the chance to move into the top four if they beat Bournemouth and other results go their way over the weekend.