Frank Lampard admits he is concerned about football in England continuing while the COVID-19 crisis escalates.
On Saturday (AEDT), London's mayor, Sadiq Khan, declared a "major incident" in the capital as hospitals face rising numbers of patients.
The English football authorities are carrying out regular tests on players and club staff, and the number of positive cases is rising, with 40 declared in the Premier League for last week.
Lampard said none of those were Chelsea players but confirmed "a small number of staff" with the London club had tested positive recently.
Monday will see Chelsea welcome fourth-tier outfit Morecambe to Stamford Bridge in the FA Cup third round, with the visitors having recently had to postpone two games because of coronavirus cases in their ranks.
Chelsea head coach Lampard was asked about possible worries, and said: "Not just about playing Morecambe, but I do have concerns because of the current climate.
"We haven't had any players positive in the last couple of rounds – we have had a small number of staff.
"Of course, whilst the country is in lockdown for a reason, while football carries on for a reason, it means there's lots of mixing going on.
"We have to be ultra-careful. I'm not completely comfortable but we have to toe the line, we have to keep playing.
"The safety must come first. There are lots of moving parts and things are changing day by day, week by week."
Burnley boss Sean Dyche this week floated the idea that if footballers were vaccinated, it would lead to savings on testing and such money could be ploughed into the National Health Service.
Lampard said, as Dyche did, that footballers should not be seen to be jumping the queue ahead of those in most need.
He said: "Maybe there's a time down the line when we look at sports but I don't think it's that time right now."
Chelsea will be without the injured Reece James, Andreas Christensen and N'Golo Kante for the Morecambe game, and Lampard is considering giving a first-team chance to a number of academy players.
Lampard's team have lost 3-1 to both Arsenal and Manchester City, either side of a 1-1 draw with Aston Villa, in a Premier League slump over the past fortnight.
Previous defeats in mid-December to Everton and Wolves have also played a part in them falling away from being challengers near the top of the table to sitting in ninth place.
They face a fourth-tier side who have won six of their previous seven games, yet this is Morecambe's fourth appearance in the third round of the cup, and they have lost each of their previous games at this stage without scoring.
Chelsea's last third-round defeat in the competition came in 1997-98, when they lost to Manchester United.
Lampard said the challenge of returning his team to peak form "makes my job more exciting".
He accepts "confidence has been hit" and said: "The players need a lift. That's my job, the staff's job, and their job. I don't know any way out of a lack of confidence but to sprint yourself out of it and fight yourself out of it, because those are the rules of football."
He was reminded about Chelsea being stunned 4-2 by Bradford City in the fourth round in January 2015 and said: "Underdogs will turn up, try to win and make things difficult for you.
"Considering our current form, we have to be even more on guard and worry about ourselves, and get ourselves playing well, because if we play well and do our job right, we'll win the game I believe."