An academy player from Edinburgh Rugby has tested positive for coronavirus.
At the Scottish government's daily briefing on Friday, National Clinical Director Jason Leitch said the player had been at a house party last week with several other team mates.
A further three youth players are also self-isolating.
Edinburgh Rugby's weekend match in France is scheduled to go ahead following an assessment by health teams.
Prof Leitch said he was "personally disappointed" as the house party attended by four youth players breached restrictions on social gatherings and protocols agreed with Scottish Rugby to allow the sport to resume.
He said: "Rugby, like other performance sports has been given the go-ahead on the strict condition that clubs and players abide by the guidance that has been agreed."
Prof Leith said he had spoken to leaders at Scottish Rugby and that they were taking the incident "very seriously indeed".
He added: "Incidents like this and the ones we've seen previously involving other sports underline a really key point.
"If at any time one of us fails to abide by the rules we put others at risk and we give the virus the chance to spread and create consequences that are totally outwith our control."
Edinburgh Rugby said potential contact by the affected player with other members of the squad had been fully reviewed by external medical professionals and no further action was required.
It said "all club personnel have been advised to remain vigilant and be aware of, and report, any subsequent symptoms".
In a statement the club added: "We would treat a suspected breach of our own, and the government's public health guidelines, extremely seriously and will take appropriate actions and steps as required.
"Our priority is to ensure the health and safety of our players and staff, and we will continue to closely monitor and support all relevant individuals.
"Both Edinburgh Rugby and Scottish Rugby will also continue to work with the Scottish government and the Lothian Health Protection Team around any further matters arising from these circumstances."