Netherlands coach Ronald Koeman was taken aback by the flu virus that swept through his squad and caused five players to be sent home on the eve of their European Championship qualifier away to France.
The Dutch announced on Thursday that defenders Matthijs de Ligt and Sven Botman, forward Cody Gakpo, midfielder Joey Veerman and goalkeeper Bart Verbruggen had all been sent home after contracting the illness.
"We do not rule out the possibility that even more players could drop out, that seems likely to me. We are a bit more careful with shaking hands, but you cannot legislate for every contact," Koeman told a news conference.
Koeman said he had received news from the team doctor early on Thursday that five players were ill.
"I was shocked. I went down to the hotel lobby I saw Joey Veerman sitting there, waiting for a taxi. Sven Botman had already left. Then you get to understand the whole situation and you have to act quickly."
Koeman called up Internazional centre-back Stefan de Vrij, Bayern Munich midfielder Ryan Gravenberch and Vitesse Arnhem keeper Kjell Scherpen as replacements for the Group B qualifier in Paris on Friday.
But he could recall the sick players if they recover in time for the Netherlands' qualifier at home to Gibraltar in Rotterdam on Tuesday.
"The five who have gone home have not yet been eliminated for the entire period," Koeman said. "It's not definitive that they will not come back. That depends on how things develop."
It was not clear how the virus had spread so quickly through the camp.
"Of course, everyone wants to know where it comes from, but we can only speculate and there's no point doing that," Koeman said. "There were players among those five who probably would have been in the starting lineup.
"But luckily I also interchanged a lot of guys in positions this week, so those who are now going to play have also trained in those positions. I've figured out how I'm going to do things.
"It's clear that this is not our normal team," added Koeman, who lost midfield ace Frenkie de Jong to injury on Monday.
"I also have confidence in the other players. Football is a strange game. We can also achieve a result with these players. It is logical that missing a Frenkie de Jong is a blow, but I don't think we have no chance."