Health and consumer protection agencies have repeatedly warned that several of these treatments, as well as vitamin infusions and expensive injections of “peptide therapies” sold at alternative wellness clinics for more than $1,000, are not supported by reliable scientific evidence.

But such unproven remedies, often promoted by doctors and companies on social media, have appealed to many people in low-income immigrant communities in places across the country where Covid-19 rates have been high but access to health care is low. Some turn to unregulated drugs because mainstream medicine is too expensive or is inaccessible because of language or cultural barriers.

“It’s disappointing but not surprising” that people living below the poverty line have spent large sums of money for unproven treatments for Covid-19, said Rais Vohra, the interim head of Fresno County’s health department. “People are desperate and bombarded with misinformation and may not have the skills, time or context to interpret medical evidence.”