Hydroxychloraquine, a/k/a plaquenil, is an anti-parasitic drug that has been used to treat uncomplicated malaria and for prevention of malaria during travel. Historically, soldiers who took anti-malarial medicines reported improvement in their rheumatoid arthritis and lupus symptoms. Today, hydroxychloroquine is used to treat lupus and rheumatoid arthritis; and it is being tested in covid-19.
If hydroxychloraquine successfully treats and/or mitigates symptoms in rheumatoid arthritis and lupus, we should ask whether rheumatoid arthritis and lupus are caused, in whole or in part, by pathogens or parasites that can be treated with an anti-parasitic drug. When something works, be happy; and also ask why it worked, what pathogens and parasites it likely worked against, and whether the success of treatment reveals something about causation.
We already have other anti-parasitic drugs available on the market; and we have other classes of drugs, such as “zoles”, “mycins”, and “cyclines”, which may be partially effective against parasitic infections. We already have drugs in need of testing and expanded indications, for other chronic diseases caused by immortal pathogens. Accepting underlying pathogens and parasites can cause chronic disease, and the impact of co-infections in covid-19 patients and other chronic diseases, opens new possibilities for treatment and mitigation of covid-19 and other chronic diseases.