COVID-19 could be a seasonal illness with higher risk in winter?
A study conducted in Sydney, Australia, during the early epidemic stage of COVID-19 has found an association between lower humidity and an increase in locally acquired positive cases. Researchers discovered a 1 percent decrease in humidity could increase the number of COVID-19 cases by 6 percent.
The problem might not be the humidity difference itself. Air that is too dry will dry out noses, sinuses and lungs making them more susceptible to everything: dust, allergens, bacteria, viruses and so on. The tissues are just dry and irritated and more susceptible to everything. Most homes in the US are way too dry once the heat is on. Many are literally as dry or dryer than the Sahara desert. Add this to closed in, no fresh air and closer quarters with other people. A recipe for disease and more. I keep my home at 40% humidity or slightly above all winter long. It absolutely does help but you do not want humidity too high or mold growth is promoted. A mold lung infection can literally be life threatening.