To put the coronavirus pandemic in perspective, consider what happened when the bubonic plague struck London in 1665. The onset of the disease could be sudden, says Yale historian Frank Snowden: “You actually have people afflicted and in agony in public spaces.” Trade and commerce swiftly shut down, and “every economic activity disappeared.” The city erected hospitals to isolate the sick. “You have the burning of sulfur in the streets—bonfires to purify the air.”

Some 100,000 Londoners—close to a quarter of the population,...