Listen to your mother and wear that sweater – or better yet, a scarf.
A new study from the Yale School of Medicine finds that the rhinovirus – the most frequent cause of the common cold – reproduces more efficiently in colder weather, and that the reason may be that our bodies become less adept at stopping the virus when it's cold out.
Cold weather, in other words, might actually lead to more colds.
“The lower the temperature, the innate immune response is reduced,” says senior author Akiko Iwasaki, a professor of immunobiology at Yale.
For roughly 50 years, scientists have known that the rhinovirus replicates most efficiently in our noses, where temperatures can be 8 to 9 degrees cooler than the rest of our bodies, especially as we inhale frigid winter air. The question, however, was why.
“Many people had focused on the intrinsic nature of the virus and not found anything concrete, so our study focused on the immune response of the body,” Iwasaki says. “It’s one of the first of its kind to even look at this question.”
Iwasaki and her team, led by postdoctoral fellow Ellen Foxman, examined airway cells taken from mice. Some of the cells were kept at 98.6 degrees, others at 91.4 degrees – the average temperature in our nostrils.
Like a radar-jamming fighter jet, the cooler temperature apparently undercut the cells’ defenses: Both the enzymes that detect viruses, and the signals that connect those sensors to the immune system, seemed to perform far more effectively at 98.6 degrees than at the colder temperature.
It’s a finding that may have implications for studying and combating a wide range of seasonal illnesses, not just the common cold.
“Other viruses tend to happen during the cold winter months, like the influenza virus,” Iwasaki says. “It’s a general suppression of the immune response in the nasal cavity temperature, so we expect that other viruses may also take advantage of this suppressed immune response.”
The most potent viruses are still those able to replicate at our higher core body temperature of 98.6 degrees, when our immune systems are most efficient. And as Iwasaki points out, exposure is just as important a factor, too: Not contracting rhinovirus in the first place will help keep the cold at bay. But, she adds, as many as 20 percent of people have the rhinovirus at any one time – and most are asymptomatic, meaning they have not come down with a cold and don't even know they have the virus.
"If you happen to be one of the 20 percent of people, maybe just going out in the cold air alone is enough to promote the replication," Iwasaki says – precisely the reason, she adds, she'll start thinking more about bundling up this winter.
“Especially,” she says, “around the nose.”
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Originally Posted by Swordsmyth
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