Premier League players and club staff will need to take a lateral flow test every day in order to get into training grounds as part of new measures agreed on Tuesday.
The action is aimed at stemming the rising number of positive cases.
The Premier League confirmed on Monday there had been a record 42 positives over the previous seven days.
It is the highest figure recorded since Covid testing began as part of Project Restart during the 2019-20 season.
Previously, the most positive tests returned in a week this season was 16 from 16-22 August, when there were 3,060 tests.
Outbreaks at Tottenham and Manchester United have caused the postponement of two league games within the space of three days, while Brighton, Leicester, Aston Villa and Norwich have all confirmed cases.
In addition to the daily tests to get into training grounds, players and staff will now have a PCR test at least twice a week, which was the case last season, before it was changed to lateral flow tests in the summer.
It is anticipated the measures will be implemented quickly in an attempt to stem the spread of the new Omicron variant of coronavirus. Additional mask wearing, limiting of time spent receiving physical treatment and social distancing are also being advised to reduce the risk of further cases.
With the season about to enter the busy festive programme, clubs will want to avoid postponements which could create a fixture backlog and potentially even leave the league open to demands for rebates from broadcast partners, which had to be paid when the 2019-20 season was suspended at the start of the pandemic.
Last week, following the introduction of new coronavirus rules in England, the Premier League told clubs to return to emergency measures, including social distancing and wearing masks.
Brighton chief executive Paul Barber told BBC Sport that his club is “now moving to testing three times a week” for players and the staff that work “in the bubble” to try to limit the number of infections that are spread from one player to another.
And from Wednesday, fans will need to show proof of double vaccination or a negative test to attend sporting events with crowds of more than 10,000 people in England. This includes Premier League games.
Stadiums have been free to operate at full capacity since final Covid restrictions were lifted in July.
Which Premier League clubs have Covid-19 outbreaks?
Tottenham’s Europa Conference League match against Rennes was called off on Thursday because of the outbreak that resulted in the Brighton postponement.
Also on Thursday, a number of Leicester players did not travel to Italy for their Europa League group game against Napoli because of positive Covid-19 tests.
Late on Monday, the Premier League confirmed United’s game at Brentford was postponed after the Old Trafford club expressed safety concerns following the closure of their training ground for 24 hours to reduce the risk of transmission.
Aston Villa boss Steven Gerrard confirmed “a couple of staff members and a couple of players” have tested positive but insisted the “vast majority” were negative.
He said Tuesday’s game against Norwich is not in doubt and Canaries boss Dean Smith said one of his players was isolating but the rest of the squad had tested negative on Sunday.
At Brighton, head coach Graham Potter says there are “three or four” positive cases.
In the Championship, QPR’s second game in a week has been called off with “a number of positive Covid-19 cases” in their first-team squad.
Saturday’s home game with Swansea is off, after Monday’s trip to Sheffield United was also postponed.
What are Premier League managers saying about Covid-19?
Before the postponement, Brentford boss Thomas Frank echoed Arsenal’s Mikel Arteta in calling for greater clarity from the Premier League over fixture changes because of Covid-19.
Manchester City manager Pep Guardiola said he encourages his players to get a vaccine booster, adding: “We speak with the players every day to say be careful. Stay healthy, wear masks, social distance.”
Conversely, Burnley manager Sean Dyche revealed that he does not “preach to the players” on vaccines, but Norwich’s Smith described the Canaries as “highly vaccinated”.
Dyche added: “We certainly have players who don’t have the full vaccination. Everyone has a choice, personally I have all three as I think it’s right to do so.”
What are the rules for fans at Premier League games?
The government’s introduction of ‘Plan B’ on Wednesday to fight the spread of the Omicron variant means it will be mandatory for fans to show proof of double vaccination or a negative test to attend sporting events with crowds of more than 10,000 people in England.
Premier League clubs have conducted spot checks on fans so far this season, with Brighton, Chelsea and Tottenham among those to make Covid passes mandatory.
Brighton play Wolves in the Premier League on Wednesday and Seagulls chief executive Paul Barber said he hoped that, as long as fans followed new measures, there would be no return of restrictions on numbers attending games.
Barber said Brighton supporters would have to complete a pre-match online declaration and “ideally” wear masks inside the stadium.
“It seems a small price to pay for keeping each other safe, protecting the NHS and hopefully keeping the stadium open with a full capacity,” Barber added.
“The government do expect us to carry out more random checking than what we’ve previously done so there is every chance it will take longer to get in.”
Sports minister Nigel Huddleston said he “appreciated” football players and staff “testing at large volumes” and said the current measures were “proportionate” and “right for now”.
Asked about levels of vaccination in sport, Huddleston added: “Lots of sportspeople have got vaccinated and they’ve been great advocates in getting other people vaccinated. I really appreciate that.
“Those who haven’t been vaccinated yet for a whole variety of reasons, I strongly encourage them to do so. There will always be some people who can’t get vaccinated, we understand that, but the key message is please not only get vaccinated but use your celebrity to make sure for the country.
“The important thing is they’re testing and at large volumes, which is great. The message to footballers, and everybody, is get vaccinated, get your booster because that’s the best way to protect yourself and others. I do appreciate the fact that football is testing a lot because that’s also important.”
What about the EFL?
In the 2020-21 season, the Professional Footballers’ Association paid an estimated £5m bill for players to be tested across the English Football League. But up to this point in the 2021-22 season, there has been no mandatory requirement for clubs to test players.
The EFL had issued guidance in July around two ‘green’ and ‘red’ protocols. Clubs have been following ‘green’ protocols of daily screening for symptoms, with stricter ‘red’ protocols including testing only triggered by any local outbreaks, further restrictions imposed by the government – as has happened in recent days.
A decision to move to ‘red’ protocols would be made by the league in consultation with the clubs.
The EFL told BBC Sport on Tuesday that “conversations on Covid matters are ongoing”.
In the meantime, fixtures are being affected in Championship, with QPR on Tuesday forced to postpone a second match in a matter of days amid a Covid outbreak at the club.
QPR have postponed Saturday’s home game with Swansea City having also been forced to call off Monday’s trip to Sheffield United.
What about in Scotland?
No new official guidelines have been put in place yet – beyond the ongoing use of lateral flow testing – albeit some clubs are taking their own extra precautions around testing.
New advice was given at the weekend around travel, with clubs told if anyone on a team bus tested positive, all passengers would have to self-isolate for 10 days.
However, that was revised after clarification from the Scottish Government. Now only household contacts or those not double-jabbed will not be able to be cleared by a negative test.