Chelsea star Callum Hudson-Odoi has tested positive for COVID-19, commonly known as coronavirus.
The 19-year-old is the first Premier League player to test positive to the illness, with Chelsea immediately closing down their training facilities.
The virus was updated to pandemic level by the World Health Organisation this week.
Arsenal and Brighton's fixture this weekend was cancelled after Gunners boss Mikel Arteta was also confirmed to have contracted the virus.
The Blues trip to Aston Villa on Sunday must also now be in jeopardy after Hudson-Odoi's diagnosis.
A club statement read: "Chelsea men's team player Callum Hudson-Odoi had a positive test result for Coronavirus returned this evening.
"Chelsea personnel who had recent close contact with the player in the men's team building will now self-isolate in line with Government health guidelines. These will include initially the full men's team squad, coaching staff and a number of backroom staff.
"It is expected that those who did not have close contact with Callum will return to work in the coming days. In the meantime, the men's team building, one of several separate buildings at our training ground, will remain closed. The rest of our training facility, Stamford Bridge and our other facilities are operating as normal.
"Callum displayed symptoms similar to a mild cold on Monday morning and has not been at the training ground since then as a precaution. However, his test came in positive this evening and he will undergo a period of self-isolation. Despite testing positive for the virus, Callum is doing well and looking forward to returning to the training ground as soon as it is possible.
"We will continue to adhere to Government and Public Health Guidelines with regard to our facilities and staff and will be discussing next steps with regards to upcoming fixtures with the Premier League on Friday morning. We will provide further updates as necessary via the club's website.
“We wish Callum a speedy recovery and look forward to welcoming him back to the club soon."
