Medicine made tremendous leap forwards during the first few decades because of the twin tragedies of the first World War and the spread of the deadly Spanish flu. At the time, there were millions of people suffering from either influenza or the gruesome wounds brought about by trench fighting.
One of the most simple and most effective medicines that doctors discovered while moving patients out of overcrowded hospitals and medical tents. It turns out the Vitamin D found in sunlight helped cure infections in skin tissue and that the fresh air helped human lungs fight the influenza virus while working as a disinfectant.
Dr. Richard Hobday wrote an article on the subject in Medium:
Put simply, medics found that severely ill flu patients nursed outdoors recovered better than those treated indoors. A combination of fresh air and sunlight seems to have prevented deaths among patients; and infections among medical staff. There is scientific support for this. Research shows that outdoor air is a natural disinfectant. Fresh air can kill the flu virus and other harmful germs. Equally, sunlight is germicidal and there is now evidence it can kill the flu virus.
The practice remained popular until the 1950s, until the discovering of life-saving antibiotics shifted the focus on their use.
During a study written up in NPR, they revealed that tests had proven that the Coronavirus, like other viruses, degrade faster in direct sunlight. However, as the knowledge base of the medical community grew, the focus became less on open air hospitals and more closed antiseptic settings. However, the pendulum is swinging back the other way. Studies have shown that that patients in rooms with windows recover faster than patients in windowless rooms.
So get some fresh air and sunlight soon.