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NPR's Patti Neighmond went looking for an explanation.
PATTI NEIGHMOND: My colleague Jane Greenhalgh got really sick last winter. So did her children. But not her husband Tom.
JANE GREENHALGH: If there's a cold going around, the kids get it. I get it. Tom never gets it. It's a bit irritating, actually.
NEIGHMOND: And studies show this kind of experience is really common. Dr. Greg Poland of the Mayo Clinic says his wife has never spent a day in bed.
GREG POLAND: We'll be sick. You know, we'll be moaning and groaning, and I'll be sick in bed with a little bell to call her because I'm so weak and can't get up. And she's just never ill.
NEIGHMOND: Poland's a cold expert, and he told us genes have a lot to do with who gets sick.
POLAND: Jane, you're married to superman. And I got superwoman. I think what we're going to find as the years go by is that Tom has a set of genes that, together, basically form an immunologic barrier for him against many of these common viruses.
NEIGHMOND: But what about me and my mother on the airplane? I figured that at 85, she was more fragile and therefore more susceptible to getting sick. I figured wrong. As Dr. Poland says, her age was probably her secret weapon.
POLAND: Your mother, who's older than you, has undoubtedly seen many more of these sorts of respiratory viruses than you and may well have encountered that one sometime in her previous 70, 80 years, and hence has some level of immunity to it.
NEIGHMOND: Once exposed, most people have lifelong immunity, but only to that one particular virus. And there are hundreds of different cold viruses. And here's where total chance comes in. If you happen to be in the line of fire of even one sneeze or a cough, the cold viruses can get you.
POLAND: Millions. There's millions and millions of them.
NEIGHMOND: And if you're not already immune, like my mother probably was, and if you're sitting in a narrow airplane seat like I was, sharing an armrest with your neighbor, you're even more at risk, because cold viruses not only travel through the air, they travel when you touch another person or even an object.
POLAND: Maybe I get up to go to the bathroom and you didn't, but the guy who went to the bathroom right before me has a cold, sneezed into his hand, grabbed the doorknob. And then I come right behind him and grab it.
NEIGHMOND: So a combination of genetics, immunity and exposure all determine whether or not we get sick. And sometimes we make it really easy for cold germs to get us. Take public gatherings, for example, like theater or church.
POLAND: Take your eyes off the speaker for a moment and look at the people around you. What you'll find is that about every minute or two, people have their hand on their face, a number of them have their fingers in their nose, a number of them will sneeze or cough into their hand. And then what they'll do is turn and extend their hand to you.
NEIGHMOND: Dr. Poland calls this a lack of respiratory etiquette. Figuring out how to stop the chain of infection is something lots of researchers want to do. Infectious disease specialist John Treanor of the University of Rochester calls it the million dollar question.
JOHN TREANOR: Why is it that some people get sick and some people don't?
NEIGHMOND: Treanor says once scientists get the answer to that question, once they figure out exactly how cold viruses cause infection and how some people's immune systems keep them healthy, then science will really be able to fight the common cold.
TREANOR: One great outcome of really understanding why some people get sick is to develop medicines or vaccines that would target those mechanisms and effectively prevent respiratory illnesses or treat them.
NEIGHMOND: Patti Neighmond, NPR News.
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