Pharmacopoeia raiders are busy, looking for Covid-19 remedies that might be hiding in the long list of tried, tested and safe drugs. I did this for smallpox a long time ago, when it was discovered that the antibiotic rifampicin blocked its growth. It turned out that the effective dose was far too high to be useful. The smallpox strain I used in this work was called Butler. It had been isolated in Rochdale during a big outbreak in 1952. Most of the 138 cases had never been vaccinated. Nobody died, because the causative virus was variola minor, very closely related genetically to classical smallpox – variola major – but very different in its clinical effects: v. minor with a case fatality rate in the unvaccinated of less than 1 per cent and v. major with a rate higher than 20 per cent.