"The health of players and staff is our priority. Given the number of players and support staff having to isolate due to COVID-19, the club had no option other than to request the match be rearranged. The Premier League Board took the decision to postpone based on guidance from medical advisors.
"We will also suspend football training operations at the Carrington Training Complex for a short period to help reduce risk of further transmission.
"We regret any disappointment and inconvenience caused to fans by the postponement."
Premier League statement.
The Premier League also issued a statement saying that will address each match and team on a case by case basis, but have no plans, as of yet, to temporarily postpone the league.
“It is with regret that this is the fourth Premier League fixture to have been postponed in the past week," their statement reads.
“While recognising a number of clubs are experiencing COVID-19 outbreaks, it is the league’s intention to continue its current fixture schedule where safely possible. The health and wellbeing of all concerned remains our priority.
“Regarding Manchester United’s game on Saturday, the club continues to have an ongoing COVID-19 outbreak within their squad, which has left them unable to field a team for the match at Old Trafford.
“A significant number of COVID-19 cases led to their game against Brentford FC being called off earlier this week, and today additional positive tests have been confirmed.
“The board assesses applications to postpone matches on a case-by-case basis, based on existing rules and COVID-19 postponement guidance issued to all clubs.
"It will assess a number of factors, including the ability of a club to field a team; the status, severity and potential impact of the COVID-19 outbreak at the club; and the ability of the players to safely prepare for and play the match. The Board must also consider the wider risks to the opposition and other people the club may come into contact with.
“In light of the recent rise in COVID-19 cases across the country, the Premier League has reintroduced Emergency Measures. These include protocols such as more frequent testing, wearing face coverings while indoors, observing social distancing and limiting treatment time.”