It is my understanding that being cold doesn’t make us sicker (aside from pneumonia) so why is there actually a season where illnesses like the common cold and flu spread faster? Shouldn’t people get sick at the same rate all year?
In: Biology
People are inside/enclosed spaces more, places are sealed up more so air doesn’t recirculate as quickly, germs stick to coats, and scarfs and gloves, etc.
It’s mostly because of the indoor environment.
When it’s cold out, people tend to stay inside and closer together. So, as density in public spaces increases so do opportunities to spread infections.
Also, air tends to circulate inside a closed system more (centralized heating) so there’s more opportunity to spread infections as people breathe in recirculated air.
And lastly, as I recall, cold weather tends to suppress people’s immune response somewhat so pathogens have more time to develop and thus spread. I’m a bit vague on that, though.
Viruses do better in colder weather than they do in hot weather, and people traditionally tend to gather around more indoors when it’s cold outside which makes it easier for these things to spread. Colder weather *does* have an effect on your body’s germ-fighting ability, too, especially in your sinuses – your nose tends to get drier in cold, dry climates. The mucus that’s normally there to filter out bad bacteria dries up and you don’t filter things out as effectively.
It’s most likely just from people being in closer proximity to each other and staying indoors more when the weather is colder. Close proximity means the viruses can spread more easily and faster
Beyond what others have said, a big contributor in the US (although not exclusive to it) is that people tend to travel for Thanksgiving and Christmas. It causes rapid spreading of germs.
Also your vitamin D levels get lower in shorter and colder and cloudier weather. Vitamin D helps immune system fight viruses and tuberculosis. Hence the cod liver oil .
[Vit D and seasonal respiratory infections](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3543548/)
[Vit D and TB risk](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5207333/)
NB: there are some studies that disagree with this.
In addition to what others have said, Uv light kills germs. It’s like a natural disinfectant. In winter there is less uv light so it’s easier for germs to spread.
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