Rugani announced he had contracted the virus on Wednesday, 72 hours after he sat on the bench for Juventus’ win over Inter Milan.
The defender shared the same dressing room as Ronaldo and the rest of his teammates at the San Siro, where the game was played behind closed doors.
Now all players from both teams have been forced to self-isolate, with Ronaldo returning to Madeira.
Northern Italy is one of the worst-affected areas in Europe, and Ronaldo will not be coming back to Turin for the time being.
All Serie A fixtures have been postponed until April 3, but Juventus are – as things stand – due to play Lyon in the Champions League next week.
The tie is set to be played behind closed doors, but now faces an increased prospect of it being put back to a later date.
Several other Champions League fixtures have been forced to prohibit fans from attending, with only Man City vs Real Madrid currently still open to supporters.
Rugani posted a message to fans on Twitter after news of his diagnosis was announced.
“You will have read the news and that’s why I want to reassure all those who are worrying about me, I’m fine,” Rugani said.
“I urge everyone to respect the rules because this virus makes no distinctions! Let’s do it for ourselves, for our loved ones and for those around us.”
President of the Italian Football Federation, Gabriele Gravina, has now put forward alternative options to conclude the Serie A season after admitting the current campaign may not be able to reach a natural conclusion.