Scottish FA chief Ian Maxwell admits he's baffled about how Billy Gilmour tested positive for covid.
The Chelsea midfielder missed Scotland's loss to Croatia on Tuesday which saw them knocked out of Euro 2020.
"You take a step back and, when Billy has his positive result, everyone looks at it and thinks, 'How can that happen?'" he said.
"But when you look at his movements, just as part of his involvement with the team, he is in a hotel in Darlington on Thursday. He is then on a bus, a plane, another bus, another hotel and into a stadium and on to another bus, another plane and so on. So when people say, 'How can that happen?', that's the difficulty of coronavirus.
"It really doesn't need very much at all and you can contract it purely from touching the wrong thing at the wrong time.
"We are well versed in the protocols, we know exactly what the risks are and we have kept the players as secure as we can with a virus which is so difficult to manage."
