Dozens of police officers have been forced to self-isolate after some positive Covid cases two weeks after Rangers' title win.
The Scottish Police Federation (SPF) said a number of officers who attended illegal gatherings of fans on 7 March have tested positive.
Other officers they had contact with were required to self-isolate.
It comes as a major police operation is planned for Sunday's Old Firm match in Glasgow.
The events at Ibrox and George Square two weeks ago have directly affected 30 to 40 officers as well as their families.
The BBC understands at least two officers involved in the policing operation later tested positive although it is not possible to determine with certainty where they were infected.
David Hamilton, chairman of the SPF, told the BBC: "It is entirely predictable and, of course, most of these officers will not have been vaccinated. It is everything we warned about.
"Our call is for people to reflect on those numbers and the impact it is having on the community through the lack of policing.
"We did not choose to be in George Square. It is something we had to do and it is part of our role."
Mr Hamilton urged both Rangers and Celtic fans to stay at home on Sunday to avoid putting frontline police officers at risk.
He described Sunday's police operation as one of the largest Police Scotland has conducted with personnel being drafted in from across Scotland.
Efforts have also been made to procure better protection for police officers, including higher-level FFP3 masks.
A total of 28 arrests were made made and seven fines issued after crowds of fans gathered to celebrate Rangers winning the Scottish Premiership.
'Infuriating and disgraceful'
Large numbers of supporters made their way to Ibrox Stadium and Glasgow's George Square to mark the achievement despite warnings to stay at home.
Nicola Sturgeon said the crowds were "infuriating and disgraceful" and could delay the end of the Covid lockdown.
Under current guidance public gatherings are banned and the "stay at home" order remains in place.
Four people from a maximum of two households are able to meet outdoors with social distancing required.
Football games are taking place behind closed doors with no fans in the stadium.
The 21 March Celtic v Rangers game was under threat of cancellation but was given the green light on Friday.
Justice Secretary Humza Yousaf said the decision to allow the game to go ahead followed "extensive engagement" with the clubs, the SPFL, Police Scotland and Glasgow City Council.
He said: "Police Scotland have confirmed there will be a significant police presence in Glasgow to maintain public safety.
"I urge the fans to listen to the messages from their clubs, the police and government to stay at home.
"I also encourage Celtic and Rangers - and all other clubs in Scotland - to continue to encourage their supporters to stay home during games until they are permitted to return."
Police Scotland warned that officers would make arrests if there were any mass gatherings after the match, which is due to kick off at noon.
Assistant Chief Constable Bernard Higgins said the clubs had acted "really, really responsibly" to convey the "stay at home" message to fans, and he urged supporters to follow this advice.
'Do the right thing'
Mr Higgins said: "Detailed plans are in place for an extensive and proportionate policing response to this weekend's match at Celtic Park.
"Our approach throughout the pandemic has been to encourage people to do the right thing to avoid the spread of the disease.
"However, where officers encounter blatant breaches of the legislation they will not hesitate to enforce the law where necessary to ensure public safety."
Responding to the positive police cases, a Police Scotland spokeswoman said: "Police Scotland is following Scottish government and health guidance and where cases of coronavirus are identified, we work with the local health board and adhere to Test and Protect procedures.
"We have sufficient capacity and as a national service Police Scotland can flex resources should there be a requirement to do so."