An old argument, continued

Cold viruses thrive in frosty conditions 

Ah, it was decades ago now that I was arguing with friends (well, more friends of friend, really) that it was not unreasonable to believe that getting a "chill" in winter made you more susceptible to catching a cold.   "Rubbish" I was told; it's an old wive's tale believed before people understood that colds were caused by a rhinovirus,  and (of course) if you don't have the rhinovirus you don't catch a cold no matter how chilled you get.   But, I said, I would guess that nearly everyone has some exposure to rhinovirus during "cold and flu season", and letting your body temperature dip may lower your immune system enough to become more susceptible to getting ill from the exposure.   "No", I was told, they've done studies about that and you are still wrong.

Well, in fact, the matter has been the subject of some contradictory studies, as I noted when I last addressed this in a post in 2005.  (I have been blogging for a long time...)

And now, further vindication (of a sort) I can claim from another study:

In an attempt to solve the cold conundrum, Foxman and her colleagues studied mice susceptible to a mouse-specific rhinovirus. They discovered that at warmer temperatures, animals infected with the rhinovirus produced a burst of antiviral immune signals, which activated natural defenses that fought off the virus. But at cooler temperatures, the mice produced fewer antiviral signals and the infection could persist.

The researchers then grew human airway cells in the lab under both cold and warm conditions and infected them with a different rhinovirus that thrives in people. They found that warm infected cells were more likely than cold ones to undergo programmed cell death — cell suicide brought on by immune responses aimed at limiting the spread of infections.

Foxman says that the data suggest that these temperature-dependent immune reactions help to explain rhinoviruses' success at lower temperatures, and explain why winter is the season for colds. As temperatures drop outside, humans breathe in colder air that chills their upper airways just enough to allow rhinoviruses to flourish, she says.

This also shows why you shouldn't lose contact with old acquaintances: it removes the fun of claiming vindication 30 years later.