What?!? Doesn't anyone read scientific journals/reporting any more. Viruses wrap up in fats to ride out cold weather outside or at high altitude. They catch a ride on a water molecule (whether water or ice). They end up on your coat, head, hands, mouth, eyes, etc. Once the temperature increases, they 'thaw' out and become 'active'.
Learn more by looking at my clip about how the flu can make you fat. Enjoy!
Certainly, trading viruses with your friends, family, and colleagues is common. Additionally, you are more likely to catch what other people have if you breathing the same air. However, most viral infections start as an invasion from outside the body.