RhinoVirus Image Source

It’s getting closer and closer to cold weather here in the north eastern United States, so maybe it’s about time we think about colds. Nobody likes getting the sniffles, and the dull aching body isn’t exactly conducive to productivity either. So let’s talk Colds!

Many of us have heard it before when we were children. It’s winter time and it’s cold out, maybe snow is falling and you just have to get outside and mess around. You’re just about to run out the door when behind you your mother is yelling, “Put on a hat or you’ll catch a cold!!”

(Source) Just look at how safe she is from the cold virus with that ho ho ho hat on!

Yeah, right MOM, most of us thought (well me at least, I was invincible as a child, and of course knew everything) what does being cold have to do with catching a cold? So you would either ignore her (like me) and run outside or begrudgingly put that hat on (like a responsible child). You may catch a cold, or you may not. Going out-side when it’s cold doesn’t have anything to do with that… right? There isn’t any science backing that up, it’s just a tale from a time before people understood science like we do now…right?

Or is it?

What Causes The Common Cold?

The disease otherwise known as the common cold is caused by a class of viruses called Rhinoviruses. They look like this:

(Source)

No wait, those are actual Rhinos. The rhino virus actually looks like the title/thumbnail image for this post, it’s a spherical shaped little bugger which has an optimal replication temperature of around 33-35 °C, which also just happens to be the average temperatures found in your nose (how convenient!).(1) These viruses enter your nose and gain access to your epithelial cells (aka your skin, and the surface of your organs…such as lungs), through interaction with a cell surface receptor called CD54 (2). This interaction allows the rhinovirus to gain access to those cells and rapidly begins proliferating. After infection with the rhinovirus symptoms usually begin within 24-48 hours (which is particularly fast, many infections take upwards of 7 days or more to cause symptoms).

Older Research

Scientists often like to research things of topical interest to people (more clicks on the papers, means better chances at future high impact journal publications and more money from grants after all!) So this was a topic that was given a surprising amount of work looking into. Early work tried to see whether viral respiratory infections were the result of being exposed to chilly air. In a review from 2002, researchers concluded that the scientific consensus at the time was that there was “no cause effect relationship between acute cooling of the body surface and the common cold.” So I guess that’s that, scientists don’t believe it case closed. Wait you want them to actually PROVE there is no causal relationship? You stickler for the scientific method you.

(Source) or maybe it’s because you hate having colds?

Cracking The Whip, Keep Testing Scientists…Get to Work!

Well as we discussed earlier, we already knew that the virus itself replicates better at cooler temperatures like those found in our nasal passages. However our immune system is strong enough to keep them at bay so the cold temperatures aren’t doing anything to make you more likely to get sick…right?

“WRONG”

In an article from 2015 published in the Proceedings of the National Acadamy of Sciences USA, researchers identified using a mouse model found that exposure of airway epithelial cells to cold temperatures resulted in a weakened immune response. This weakened response was due to decreased RIG-I–like receptor (RLR)–dependent interferon secretion (interferons are compounds that inhibit viral replication). So cold air actually reduced the airway cells ability to fight off the rhinovirus. AKA, breathing in cold air made it easier for the cold virus to infect (at least in the mouse model). Breathing in cold air really did lead to an increased likelihood of catching a cold.

GASP… Mom was… RIGHT?!?! Yes, and no.

Last I checked you don’t breathe out of the top of your head, and that hat isn’t keeping your nasal and respiratory pathways warm when you are outside in the winter.

Still, it does look like winter weather increases your chance to be infected by the cold virus through weakening your airway cells abilities to fight off a virus that already has an advantage in the cooler weather. Which means the "Old Wives Tale" is in fact true and you can catch a cold from the cold, though maybe not for the reasons they originally thought. Additionally, the hat isn’t going to make your body temperature any lower, so I guess mom wasn’t as far off as child like me scoffed at, and her heart was certainly in the right place.

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Referenced Materials

1. https://microbewiki.kenyon.edu/index.php/Nasal_passageway
2. http://atlasgeneticsoncology.org/Genes/ICAM1ID40909ch19p13.html
3. https://www.ncbi.nlm.nih.gov/pubmed/12357708
4. http://www.pnas.org/content/112/3/827.abstract

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