Scotland midfielder John Fleck has tested positive for Covid-19 at the squad's training base in Spain.
Fleck will undergo a period of self-isolation and won't fly to Portugal for Scotland's friendly match against the Netherlands on Wednesday night.
The Scottish FA says the rest of the squad recorded negative results on Tuesday after being retested.
The 29-year-old Sheffield United midfielder is part of Steve Clarke's 26-man squad named for this summer's rescheduled European Championship.
Billy Gilmour and Scott McTominay will not be available for the match against the Dutch due to their involvement in the Champions League and Europa League finals respectively.
Scotland arrived in La Finca, Spain last Thursday to prepare for the friendlies against the Netherlands and Luxembourg before travelling to Middlesbrough for the Euros.
It will be the first time in 23 years the Scots have competed in a major tournament.
The Tartan Army are in Group D with England, Croatia and Czech Republic.