According to the statement, Ronaldo is “well, symptom-free and isolated”.
The 35-year-old Juventus forward played for Portugal against France in the Nations League on Sunday and against Spain in a friendly last week.
Ronaldo will now miss his country’s next Nations League game against Sweden on Wednesday, as well as upcoming Juventus fixtures, which include a Serie A clash with Crotone and a Champions League group game against Dynamo Kyiv.
Despite the surge in Covid-19 cases across the world, many footballers have left their clubs to play international matches.
However, some clubs have not allowed players to play for their country, including Austrian club RB Salzburg whose players have been called up for Mali, Cameroon, Zambia, Austria and Hungary.
The forward has scored three league goals in two appearances for Juventus so far this season – one against Sampdoria and a brace against AS Roma.
He has also scored twice as Portugal beat Sweden 2-0 in the Nations League last month.
With his first goal against Sweden, Ronaldo became the second player to reach the 100 international goal mark. He now has eight goals behind Iranian Ali Daei’s all-time international record of 109.
Earlier this year, Ronaldo returned to his native Madeira when coronavirus cases started to increase across Europe and football was suspended, according to Reuters.
He went on to help Juventus win the Serie A title after the league took over.