What happen when germs go into space on a rocket and come back to Earth? They become stronger and deadlier than ever:
Scientists wanted to see how space travel affects germs, so they took some along — carefully wrapped — for the ride.
The result: Mice fed the space germs were three times more likely to get sick and died quicker than others fed identical germs that had remained behind on Earth.
Link - via Super Punch
More importantly, don't let the mutated germs roam free when they get back from space, I think.