Surveillance Technology Will Only Get More Intense After Covid

When an outbreak of the bubonic plague swept through Europe in the 16th century, people in London were told to stay home for a month if anyone they lived with had contracted the disease. So long as they carried with them a long white stick, known as a plague wand, one person from an infected household could venture outside to get food or other supplies. The stick served as a warning sign. It told other people to stay away.

Today, in the grip of the Covid-19 pandemic, the advice is the same: Stay home and avoid other people. But in ...