Can cold weather give you a cold?
No. But also, it’s complicated…
“Put on a sweater or you’ll catch a cold”-Anyone’s Grandmother
Infection depends on three things: exposure, dose, and susceptibility. If you’re not exposed to a virus (intact “live” virus), you can’t be infected. The same goes for any other microbe as well. I wasn’t worried about catching Ebola during the 2014–16 outbreak: because I didn’t travel to West Africa and contact bodily fluids from an infected individual. Since I did not do these things, I had no exposure to the virus, and didn’t catch Ebola!
The viruses that cause the “common cold” are rhinoviruses and coronaviruses. Like Ebola, the genetic information of these cold viruses are encoded by RNA, and they require host cells to replicate. Unlike Ebola, rhinoviruses are highly contagious, which is why they spread so rapidly (many people in the office catch one infection). These cold viruses can even be airborne: this can happen when exposed to small droplets from a sneeze or cough — so an infected person must be nearby — and these droplets are only infectious in the air for a short time.
In short: to catch a cold, you must be exposed to a person infected with a cold-causing virus. Sorry, Granny, but the cold weather won’t give me a cold. But it turns out Granny wasn’t completely wrong: cold temperatures can make you more likely to get infected.
Cold viruses seem to circulate more during cold weather, but why? It turns out that two factors seem to be working to help the virus. Rhinoviruses reproduce more with colder temperature (increasing dose), and immune responses are impaired (increasing susceptibility).
In a really clever paper from the Yale laboratory of Dr. Akiko Iwasaki, published in PNAS in 2014, the researchers showed that innate immune defenses against rhinovirus were impaired in cold temperatures (33C), and much stronger at warm “body” temperatures (37C). Since the virus replicates in the nose and upper airway, when you breath cold air your cells may have lower ability to resist infection.
So if the weather is cold — but you have to keep breathing — what can you do to protect yourself? First: wash your hands. Second: avoid sick people. Third: wash your hands. Why all the emphasis on hand washing if rhinoviruses can be airborne? It turns out that just because they can doesn’t mean they usually are. In an interesting historical experiment, described here, Sir Christopher Andrews (who discovered influenza) “marooned 12 volunteers on a deserted island” where he exposed them to people infected with cold viruses, to try to study airborne infection, but no one caught a cold. The 1978 review article by Drs. Gwaltney & Hendley — cleverly entitled “Rhinovirus Transmission: One If by Air, Two If by Hand” — goes on to summarize multiple studies that show that cold viruses are almost always spread by contact.
So though you may not be able to do much about your decreased immune response in cold weather, you can follow Granny’s other advice and “wash your hands.”
For more, follow me on Twitter @sciencethomas
Other articles by Thomas Packard:
•Think HIV is Cured? Not Yet
•The Flu Shot Can’t Give You the Flu
•Fighting the Plague — A Story of HIV/AIDS
•Antibodies: Friend & Foe
•Shrinking funding for scientific research shrinks the economy
Note: This and other things I write are my opinions about science and medicine, they should not be considered medical advice. If you have personal questions or concerns, talk with your doctor about these topics.
