📓 cold weather v colds

• Some people (like my mother) believe that "cold" (ie. low temperatures) cause "colds"
  • I was skeptical, but, something needs to account for flu-season peaking in cold-months
• Does cold weather "cause" colds?
  • Literally? No, viruses cause colds. (many different kinds)
• Does cold weather "increase the likelihood" of catching a cold?
  • schools in session
  • lower humidity -> drier mucosa in nasal passages
  • more indoors (closer together, recycled air)
  • slightly lower body temp (33C, typical in nose) -> certain immune cells work less effectively -> virus spreads more
    • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4311828/
  • lower vitamin D levels, which impact the immune system
  • less sun (UV irradiation), lower temperatures, lower humidity -> viruses survive longer in environment, spread better through air
    • https://journals.asm.org/doi/full/10.1128/JVI.03544-13
    • https://www.nih.gov/news-events/nih-research-matters/flu-virus-fortified-colder-weather
  • cold -> vasoconstriction -> less white blood cells to mucosa
    • https://www.researchgate.net/profile/Ronald-Eccles/publication/11099267AcuteCoolingoftheBodySurfaceandtheCommonCold/links/0deec518fe33a054bc000000/Acute-Cooling-of-the-Body-Surface-and-the-Common-Cold.pdf

- Summary:
- during "cold season", people are constantly exposed to cold viruses, but at sub-clinical level
acute cold exposure may increase the odds of a sub-clinical infection becoming a clinical infection