Two Championship matches scheduled for Saturday have been postponed after Bristol City and Luton Town reported COVID-19 outbreaks in their squads.
City were scheduled to play second-placed Brentford while Luton were set to host Queens Park Rangers. The positive tests come three days after Luton hosted City and beat them 2-1.
City said their players showed COVID-19 symptoms but could not test the entire squad and staff as the testing laboratory was closed with Friday being a New Year bank holiday.
This is City's second major brush with COVID-19 after their Failand training ground was closed in November following a number of positive cases at the club.
Luton said there were positive cases among their senior players, staff and immediate members of family which meant others who were in close contact had to go into self-isolation.
Meanwhile, West Ham's Ryan Fredericks has tested positive for the virus with manager David Moyes announcing the Premier League club will close their training ground for four days.
The defender missed Friday night's 1-0 win at Everton and is now isolating.
"Ryan is fine, he had a positive test so we have just got on with it," he said. "We are going to make sure we give the players four days off so they can have some time and we make sure we shut the training ground down for a few days because it is very bad, COVID, at the moment.
"The only reason is so we can get another clean and keep people out, we have not been told to do that and it is not because of the one COVID player we have got.
"We want everyone to take responsibility. It is so difficult at the moment with COVID."
Three top-flight matches were postponed in December after numerous positive cases at Newcastle United, Manchester City and Fulham.
City manager Pep Guardiola says the club will have five players unavailable for Sunday's clash at Chelsea following positive coronavirus tests.
The Citizens' game at Everton on Monday was postponed at short notice after three more players tested positive for COVID-19 following positive tests returned by Kyle Walker and Gabriel Jesus on Christmas Day.
The latest results bring the total number of isolating first-team personnel at the club to seven, including two other staff members.
In the US, the Los Angeles Chargers placed wide receiver Keenan Allen on the reserve/COVID-19 list.
Allen is tied for fifth in the NFL with 100 receptions and was recently selected for his fourth Pro Bowl.
Tight end Hunter Henry remains on the COVID-19 list and will miss his second straight game Sunday at Kansas City.
The New Orleans Saints confirmed running back Alvin Kamara has also been placed on the reserve/COVID-19 list after testing positive for the virus.
Kamara is out for Sunday's game against the Carolina Panthers and his postseason eligibility - at least for the wild-card round - is now in question.