Here's what we do know: being around lots of people, especially while doing something stressful like traveling, makes you more likely to get sick. Weiss' advice, even after observing so few coughing fits and viruses in the field, is to practice good hygiene and to keep your hands away from your face. Planes aside, we should all probably be washing our hands more. "I suspect that many people do not understand the importance of good hand hygiene," notes Weiss. And he's right. Many of us don't even realize how we get sick: sharing a water glass with a sneezy friend isn't dangerous because you might drink their backwash, but because you're liable to touch your face not long after touching the glass (the average person touches their face about 3.5 times every hour) which means you'll get their virus or bacteria right into your vulnerable mucus membranes.