Last year, the northern Brazilian city of Manaus became a textbook example of what can happen when the coronavirus is left to spread unchecked. In April, the 2-million-people city in the middle of the Amazon rainforest made it to the front page of international newspapers, with macabre scenes of tractors digging mass graves to make room for an unprecedented number of Covid-19 victims. The municipal health network collapsed, and over 100 deaths were being recorded in Manaus hospitals every day.
By the second half of 2020, it appeared Manaus had weathered the worst of the crisis. One group of researchers even suggested that Manaus had attained “herd immunity,” which would have made it the first city in the world to reach this much sought-after mark.