There have been a few instances, IIRC there was an Apollo mission that had a head cold spread among the whole crew.
But that's unlikely to be the case here because they've been up there isolated for over 6 months now
Would it be possible for some food to have been contaminated with something? It seems unlikely.
> IIRC there was an Apollo mission that had a head cold spread among the whole crew.
Yep, Apollo 7.