During the 1918 flu virus scare, about 27% of the world became infected, based on estimates. There were so many sick people that they began to put them outside in the summer in tents. But an odd thing happened. They found people outside in the tents fared better than people in closed up hospitals.
The possibilities are: the sunshine helped the people make vitamin D3, which helps the immune system, and the breeze in the tents blew away the virus particles away from patients. So, is it that fresh air is important, or simply getting rid of virus particles floating on water droplets important? Possibly a bit of both.
There are many city histories of the 1918 flu here: https://www.influenzaarchive.org/index.html
More info on open air treatment of 1918 flu patients: https://flutrackers.com/forum/forum/welcome-to-the-scientific-library/-1918-pandemic-data-stories-history/40316-1918-open-air-treatment-of-influenza
Observations.
The facts are that the patients do not thrive as well in any ordinary hospital, no matter how well it is ventilated, as they do when they are put right out into the open.
The objection to the sun parlor is that one gets direct sunlight only during part of the day, whereas the patient who is out in the open gets the direct sunlight all day long.
which is from http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1362338&blobtype=pdf
If you are sick, and it’s warm enough outside, it may be a good idea to get outside in the sun and fresh air.
