Valencia have announced that five people among the players and staff at Mestalla have tested positive for coronavirus, including Argentine defender Ezequiel Garay.
The centre-back, who was due to miss the rest of the season after undergoing surgery on a ruptured anterior cruciate ligament last month, made the announcement on Instagram on Sunday but said he feels "very well".
La Liga is currently at the start of a two-week break on all fixtures while the Spanish government is set to declare a 15-day national lockdown on Monday in an attempt to fight the Covid-19 pandemic.
Garay wrote on social media: "It is clear I have started 2020 badly.
"I have tested positive for coronavirus but feel very well. Now it only remains to pay attention to the health authorities and, for now, be isolated."
Valencia have released an official statement via their website confirming four more positive tests, which reads: "Valencia CF inform that five positive cases of the COVID-19 coronavirus have been detected amongst first-team staff and players.
"All of these persons are now at home, in good health and obeying self-isolation measures.
"Besides the information that will be provided over the coming hours, the club reiterates our support for the health authorities and their social awareness campaigns, and emphasise to all of the population the importance of staying at home and continuing to follow the previously published hygiene and illness-prevention measures."
Garay, 33, has racked up 17 La Liga starts for Valencia this season and four in the Champions League.
Albert Celades' team are seventh in the Spanish top-flight, four points adrift of fourth-placed Real Sociedad in the race for Champions League qualification.
Valencia's latest adventure in Europe's elite competition came to an end last week as they suffered a 4-3 defeat against Atalanta at Mestalla.
The Italian outfit progressed 8-4 on aggregate, with the second leg becoming the first Champions League fixture of the season to be staged behind closed doors.
UEFA has since postponed all competitions indefinitely, with talks over the status of the remainder of the 2019-20 campaign set to take place on Tuesday.