German coach Joachim Loew said a third of his squad had complained about sore throats and high temperatures.
Loew said the problems were likely the result of travelling long distances and adjusting to the different temperatures and climates in Brazil.
The Germans have played four matches so far, one in tropical heat, one in a heavy downpour and another in chilly conditions.
But Loew said the symptoms were starting to ease and he expected none of his players would be forced to miss the match.
“It was the case yesterday that nearly a third of our players were complaining of sore throats,” Loew told a news conference after the team trained at the Maracana on Thursday.
“It was a bit of a problem yesterday, but sometimes you have to wait a day to see how it develops. Like Mats Hummels, it was a bit worse on the second and third day, as he had a fever.”
Loew did not name all the players who had been effected but it was already known that Hummels was sick.
The defender missed Germany’s round of 16 match against Algeria on Monday due to a fever. He said on Wednesday he had recovered and posted a picture of himself sitting on the beach.
The only player to miss training on Wednesday was reserve midfielder Christoph Kramer, who was suffering from a case of the chills.
But he joined his team mates on the pitch on Thursday and Loew said he expected everyone to play unless they worsened overnight.
“From yesterday to today none of our players have a temperature and all of them could train,” Loew said.
“Some of them still have a bit of a cold but it hasn’t been the case that they have had any feeling of tiredness.
“I hope they all remain stable until tomorrow and that overnight we don’t see any deterioration.” (Reuters)