I think there is a readily available substance that could possibly help people prevent/treat covid-19. The problem is that no one is doing further research on this substance. The substance is stevia, the sugar substitute derived from the leaves of the stevia plant.
Right now it is only beginning to be researched and used to help treat Lyme disease (because of its ability to break up the Lyme disease biofilm).
This is a 2009 Russian study (in vitro) that shows that stevia has virustatic and virucidal (prevents growth of viruses; kills viruses) against a human coronavirus ((Hco V-229E). Download to read the whole paper:
This study shows that stevia can have an important anti-inflammatory effect that could make it beneficial in fighting Covid-19:
And this analysis of published papers shows why the above study could be beneficial in fighting the inflammation caused by Covid-19:
In the absence of any useful measures to prevent/treat Covid-19, particularly if one is told to fight the disease at home, I am choosing to use stevia regularly.