Seven German players are suffering mild flu symptoms ahead of the quarter-final match against France in Rio de Janeiro.
Coach Joachim Loew confirmed the news in a German radio interview, but he did not identify the players.
"Seven players have somehow come down with slight cases of the flu," Loew was quoted telling Germany's ARD radio.
He said that most had "throat aches", but he did not reveal their names.
"As a result, it's too early to make any final decisions about the line-up," Loew added.
Defender Mats Hummels missed Germany's round of 16 match against Algeria on Monday due to a fever.
He said yesterday he had recovered and posted a picture of himself sitting on the beach.
Reserve midfielder Christoph Kramer was suffering from a case of the chills and was the only player who did not take part in the training session, said assistant coach Andreas Koepke.
Loew has said 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, along with air conditioning, had taken their toll.
"I hope they're all doing well now," Loew said. "It's not all that bad at the moment. I don't want to dramatise it."
So gut wie wieder hergestellt :) Almost back at 100% :) pic.twitter.com/Mp1ncU81fw— Mats Hummels (@matshummels) July 2, 2014