Premier League side Watford on Tuesday confirmed that their three people have been tested positive for the virus.
Of the three diagnosed with COVID-19, one is a player and two are members of staff, the club said.
“Watford Football Club confirms that three people have tested positive for the Covid-19 virus following testing at the training ground over the past 48 hours,” the club said in a statement.
“Of those three positive tests, one is a player and two are members of staff. All three have asked that medical confidentiality be respected and, therefore, the club will not be naming those involved.
“All three will now self-isolate for seven days – in line with the protocols set out in Premier League guidelines – before being tested again at a later date,” it added.
The statement further said: “Strict adherence to the Premier League guidelines has ensured the training ground remains virus-free and a safe environment for the players to continue to work.
“The club will continue to liaise closely with the affected personnel and there will be no further comment.”
Earlier, Premier League had confirmed six positive cases of coronavirus at three clubs after players and staff were tested ahead of a return to training.
“The Premier League can today confirm that, on Sunday 17 May and Monday 18 May, 748 players and club staff were tested for COVID-19.
“Of these, six have tested positive from three clubs,” the Premier League said in a statement on Tuesday.