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❄️ Why do we get sick more in winter?

Connect indoor contact, winter humidity, respiratory-particle physics, virus stability, and nasal defenses without mistaking cold weather for the infectious agent.

3
lessons
~10 min
to learn
🔬 Science
subject
Adults
level
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What you’ll learn

  1. Winter Changes Encounters Before It Changes BodiesExplain how indoor mixing, susceptibility, and pathogen-specific timing shape winter respiratory illness.Winter changes contact networks and epidemic thresholds, but different viruses and climates follow different calendars.
  2. Cold Dry Air Changes the Transmission MediumDistinguish absolute from relative humidity and trace effects on particles, virus stability, and indoor exposure.Cold heated air becomes dry, changing particle physics and favoring influenza transmission under studied conditions.
  3. The Airway Is Part of the Seasonal SystemConnect mucociliary and nasal innate defenses to environment while preserving the requirement for a pathogen.Local airway function can be seasonally modified, but cold is a probability modifier rather than an infectious cause.

Questions this course answers

Match each winter change to the transmission factor it most directly alters.

Seasonal spread reflects people, immunity, and environment together; weather does not act through one pathway.

Put one humidity-mediated transmission sequence in order.

Heating cold air lowers relative humidity, which changes emitted particles and can favor transmission for some viruses.

Why does feeling cold not prove that cold weather caused a respiratory infection?

Cold and dry conditions affect probabilities at several stages, but they do not replace the infectious agent or its incubation process.

Grounded in trusted sources

  • Lowen et al., Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature — https://pmc.ncbi.nlm.nih.gov/articles/PMC2034399/
  • Shaman and Kohn, Absolute humidity modulates influenza survival, transmission, and seasonality — https://pmc.ncbi.nlm.nih.gov/articles/PMC2651255/
  • Shaman et al., Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States — https://pmc.ncbi.nlm.nih.gov/articles/PMC2826374/
  • Huang et al., Cold exposure impairs extracellular vesicle swarm-mediated nasal antiviral immunity — https://pubmed.ncbi.nlm.nih.gov/36494212/
  • Peci et al., Effects of Absolute Humidity, Relative Humidity, Temperature, and Wind Speed on Influenza Activity — https://pmc.ncbi.nlm.nih.gov/articles/PMC6414376/
  • Neumann and Kawaoka, Seasonality of influenza and other respiratory viruses — https://pmc.ncbi.nlm.nih.gov/articles/PMC8988196/

Every Wunder lesson is built from real, reputable sources — never invented.

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