Seven of the Germany squad have complained about the same illness that caused defender Mats Hummels to miss the last 16 victory over Algeria on Monday.
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"One-third of our team were complaining about sore throats and perhaps we were contaminated because of different temperatures and air conditioning," he said.
"Mats Hummels ran a fever but yesterday and today all players were able to train. They still have a slight cold but there is no feeling of exhaustion. I hope it doesn't get worse overnight."
Germany have been criticised for their performances so far in the tournament, especially after they scraped past Algeria in the last round with a 2-1 victory after extra-time.
Low has found himself under particular scrutiny for his use of captain Philipp Lahm in central midfield rather than right-back, but the 54-year-old says he will not be swayed by the opinions of other and is not concerned by speculation over his future.
"I don't think it's out of the ordinary that people discuss my future," Low said. "In South Africa, people were asking the same after the second match. I couldn't care less what people say.
"In other countries where they have gone home and are on holidays, it's fair enough to talk about the coach. But we are here, we are in the last eight and want to reach the semi-finals.
"We wonder how we can win, not what might happen if we lose. I've had pressure before at various tournaments and I know there are dissenting views.
"I don't think we have shown a great performance so far. We have not delivered our best and we were very bad in the first half against Algeria.
"I don't any team in the World Cup has reached their peak performance. We've had a lot of extra-time and late goals. It's not always possible to deliver top performances. It's not a computer game."