Corrected entry: The 'German language', which the people on the plane at the beginning speak, sounds very much like the actors come from Eastern Europe. The old couple and the flight attendant speak German with a heavy accent. The flight captain's German is grammatically wrong and also doesn't sound like he is a real German. Are there no unemployed German wannabe-actors in Hollywood? And the Danish guy doesn't even try to speak German when most of the Danish people speak at least a bit of German. He just says "I'm from Denmark". Chances are big he also could have tried to say that in German.
Correction: My dad speaks German. Low German. My stepmother speaks German.but they are completely different dialects and accents. Eastern European German may sound different if the person lived most of their life in East Germany, which had a Soviet occupation for almost 50 years. There's a strong Russian influence on language for Germans from East Germany. Define a 'real' German. "Most" Danes speaking a little bit of German doesn't mean they all do, just as most Canadians aren't bilingual in English and French, even though it's officially a bilingual country.
Correction: Actually, they stated that they had lowered the guy's body temperature enough to make the infection spread really slowly, so if the characters were in the room with him, they wouldn't be affected if the infection could only travel so fast.