Coach David Moyes and players Issa Diop and Josh Cullen tested coronavirus positive, West Ham announced on its official website.
Moyes, Diop, and Cullen left the stadium on the day of the League Cup match against Hull and returned to their homes after they found out they were positive.
They must follow the prescribed protocol and will be in self-isolation for 14 days, although none of them have symptoms.
Despite the coach and two West Ham players being positive, there was no postponement of the game against Hull.
