Mexico City is the first major global city to adopt what amounts to a test-and-treat approach to covid-19 involving ivermectin. But it was the largely indigenous southern state of Chiapas that led the way last summer. In July 2020, as Mexico was buckling under its first wave of the pandemic, the state decided to distribute ivermectin as a Covid-19 treatment, having already deployed the medicine in its battle against mosquito-borne RNA viruses such as Zika and Chikungunya. Since October Chiapas has consistently occupied the lowest risk level on the federal government’s coronavirus stoplight map.