Sore Throat and Runny Nose?

The morning after flying on the plane home from MI, I woke up with a sore throat and runny nose. About two days later, I was feeling much better, but Ken seemed to be sick with the same symptoms. And now that I've been home a week, I woke up again today with the same symptoms. So what gives? It's sunny outside and beautiful during the day, and I'm sniffling and can hardly talk... Who knows...