Pep Guardiola fears that next month's international break could lead to a rise in coronavirus cases in football, potentially undoing months of hard work to contain the spread.
Guardiola will take his table-topping Manchester City side to Everton on Wednesday, fulfilling a Premier League fixture postponed on December 28 due to a number of positive cases within the City camp.
Around the time the game was called off there were concerns the league could face another hiatus as a number of clubs were forced to close training grounds, but what Guardiola called an "exceptional job" from the Premier League in tightening protocols led to a significant fall in cases in January.
Last week, 2,970 tests of players and staff across the league found two positive cases – compared to 36 from 2,593 tests between January 4-10 and 28 from 1,311 tests between December 28-31.
But with national teams due to convene in the last week of March, Guardiola is concerned more problems could lie ahead.
"Hopefully not, but the only way to be protected from this virus is to stay at home and don't move, social distance and not make contact, not travel," Guardiola said.
"Now the people are going to travel and the players are going to their national teams. It is difficult enough to control it and I think something is going to rise unfortunately.
"I would like to guess it is not going to happen but experience says it has happened in two or three waves already in the world so if you move, you take a risk to be contaminated again."
Guardiola said clubs had received no guidance regarding the window but said City would give advice to their own players before they travel.
"I think the Premier League should be concerned about this, and all the leagues should be concerned," he added.
"I know the national federations need to play for qualification and to prepare for the Euros, this is normal, but the reason why there are not a lot of cases in the Premier League now is that people don't move – they go home-training centre-home or home-game-home, no more than this.
"We are in the bubble and every two days we are tested. The moment you take planes and move places, I don't know, everything can happen."
City will have Kevin De Bruyne back in contention to face Everton after almost a month out with a hamstring problem while Sergio Aguero is due to start on the bench.
But the in-form Ilkay Gundogan will not travel after pulling up with a groin problem during Saturday's 3-0 win over Tottenham – in which he scored a brace after winning a penalty.
It is yet another muscular injury in a season when managing players' fitness has been key, but Guardiola said it was not a serious one and suggested Gundogan could be back either for the weekend trip to Arsenal or next week's Champions League clash with Borussia Monchengladbach.
"He feels good, but he will not travel because we don't want to take risks," Guardiola said.
"Maybe if it was a final or something special we would take a risk but at the moment we don't want to lose him when there are many, many games ahead.
"It's not a big, big issue but we have to be careful."