How real is the risk of a second wave of Covid-19?

Scientists have set out three possible scenarios for how the next phase of Covid-19 will evolve, but none of them predict the disappearance of the virus

Epidemiologists trying to predict what Covid-19 has in store see several potential possibilities

Pointing to a graph showing a flattened curve, Suzuki Naomichi, the governor of Hokkaido, the second largest island of Japan, announced in the middle of March that the region had contained its coronavirus outbreak and could therefore lift its weeks-old state of emergency.

“We were on defence until now, but we hope to enter a new stage,” he said.

Less than a month later, he reimposed a state of emergency, warning that Hokkaido was “facing ...