Seven Germany players are suffering from flu symptoms, just 24 hours before their World Cup quarter-final against France.
Coach Joachim Low said that most had “throat aches” but did not reveal the names of the players affected.
“It’s too early to make any final decisions about the line-up,” said Low.
Mats Hummels and Christoph Kramer had suffered with illness earlier in the week, with the former missing Monday’s last-16 win over Algeria.
Low believes that the travel across Brazil, and different climate zones for their four matches so far – as well as matches in tropical heat, a heavy downpour and then in chilly Porto Alegre – had taken their toll.
But he added: “It’s not all that bad at the moment. I don’t want to dramatise it.”