The infection viral dose is currently estimated at 100 virions. The amount of a prophylactic antiviral blocker at this stage would theoretically then be very low. L-quinine may be more potent and effective than low dose hydroxychloroquine, considering the natural source of l-quinine contains the pure desired enantiomer, versus HCQ is synthetic and composed of four enantiomers that probably competitively inhibit the binding of the desired enantiomer. Thus 20mg (one glass of tonic water) may have more biological activity than 100mg of HCQ. Side-effects of 20mg appear to be nil to nonexistent, as million of people have imbibed this over the centuries. Obviously, one should get their physicians' advice on this. Another point is that there are billions of people on this who do not have readily available medical access, but they do have access to tonic water, or may already use it to prevent other viral and protozoal infections. Millions of people already do this chronically for prophylaxis, and the risk is low. For a placebo controlled double blind study to be done, this could take years, and is unlikely to be done because there is no large amount of money to be made anyway. Tonic water is a dollar a bottle and lasts for a week at this dose. Risk: Nil (if not contraindicated). Benefit: Possibly thaumaturgic!