QPR did not specify the number of players and staff who were affected but said it had left them with 'insufficient numbers to fulfil the fixture'.
In accordance with EFL regulations, the circumstances of the postponement will be investigated and a rescheduled date announced in due course.
A QPR club statement read: "Monday's Sky Bet Championship fixture between Sheffield United and QPR has been postponed.
"The circumstances surrounding the postponement will now be the subject of an investigation in accordance with EFL regulations. A rearranged date for the fixture will be announced in due course.
"We apologise for any inconvenience caused and will update supporters with further information as soon as it is available."
QPR, who are currently fifth, are next scheduled to be in action at home to Swansea on December 18, whilst Sheffield United take on Fulham on December 20,
QPR's fellow London club Tottenham saw their matches against Rennes and Brighton called off earlier this week due to an outbreak of their own.
Manchester United and Aston Villa have also reportedly been hit by COVID outbreaks.
According to SunSport, United have now had positive lateral flow tests returned on a number of players and staff.
It's reported that the entire squad who travelled to Norwich tested negative beforehand, but there have since been a small number of positive tests among players and staff on Sunday.
According to The Athletic, Aston Villa have also suffered an outbreak and cancelled training on Sunday as a result.
Of their cases, it's reported that only one is a player.