Brazil ignored the warnings. Now, while other countries fret over a second coronavirus wave, it can’t get past its first.

Weeks ago, when this seaside metropolis had recorded fewer than 10,000 cases of the novel coronavirus and there still appeared to be time, some of Brazil's most respected scientists made their last-ditch appeal. The country had reached a pivotal juncture. Cases were skyrocketing. The hospital system was teetering at capacity. Thousands had already died. So Carlos Machado, a senior scientist with Brazil’s Oswaldo Cruz Foundation, wanted the language to be strong. At the request of Rio officials, his team was assembling a list of recommendations. He needed to make clear what would happen if they didn’t immediately impose a complete lockdown. “It would result,” the team warned in the early-May report, “in a human catastrophe of unimaginable proportions.”