Do Curfews Slow the Coronavirus?

With coronavirus infections rising and a contagious new variant threatening to accelerate the pandemic, France has implemented a stringent 6 p.m.-to-6 a.m. curfew. Citizens nationwide are sequestered indoors, and businesses must close down.

In Quebec, Canadian officials imposed a similar restriction earlier this month, running from 8 p.m. to 5 a.m. It has frayed nerves: Notably, a woman who was walking her boyfriend on a leash at 9 p.m. has argued that this was permitted during the curfew, surely one of the pandemic’s most unexpected moments.

The question for scientists is this: Do curfews work to slow transmission of the virus? If so, under what circumstances? And by how much? ...As the pandemic unfolded, Australia and many European countries imposed curfews, on the theory that keeping people at home after a certain hour would slow viral transmission. Usually curfews were implemented alongside other measures, like closing businesses early and shuttering schools, making it difficult to tease out the curfew’s effectiveness.

The scientific evidence on curfews is far from ideal. There has not been a pandemic like this one in a century. While curfews make intuitive sense, it’s very hard to discern their precise effects on viral transmission, let alone transmission of this coronavirus.

Ira Longini, a biostatistician at the University of Florida, believes curfews are, on the whole, an effective way to slow the pandemic. But he acknowledged his view is based on intuition.

“Scientific intuition does tell you something,” Dr. Longini said. “It’s just that you can’t quantify it very well.”

Maria Polyakova, an economist at Stanford University, has studied the effects of the pandemic on the U.S. economy. “In general,” she said, “we expect that staying at home mechanically slows the pandemic, as it reduces the number of interactions between people.”

“The trade-off is that the reduction in economic activity especially hurts many workers and their families in the large service sector of the economy,” she added. So is the curfew worth the price?

She is at a loss to understand the logic. “Assuming that nightclubs and such are already closed down anyway, for instance, prohibiting people from going for a walk around the block with their family at night is unlikely to reduce interactions,” Dr. Polyakova said.

Moreover, the virus thrives indoors, and clusters of infection are common in families and in households. So one daunting question is whether forcing people into these settings for longer periods slows transmission — or accelerates it. ...