How effective are nighttime curfews?

Nocturnal curfews will be applied if the incidence of coronavirus cases of 100 new infections per 100,000 inhabitants is crossed. This is what the draft of Germany's new Infection Protection Act says. So far, curfews in Germany have only been used selectively.

Other countries are using them more extensively: France and the Netherlands, for example, but also Turkey, Morocco, and Tunisia. In Argentina, nighttime restrictions have been in effect again since Friday for more than half of the citizens.

The argument in favor of nighttime curfews is: Infections often happen in private. According to the theory, such contacts and thus the spread of the virus can be reduced by curfews.

A majority of Germans would support them if they were only allowed to temporarily leave their homes at night in exceptional cases to combat the pandemic. At the beginning of April, 56% were in favor of the measure in a survey by the polling institute YouGov, 37% were against it. The results are reported to be representative of the adult population.

But are night curfews even effective?

Reproduction rate falls

According to a study by researchers, mostly from British universities, a nighttime curfew could have a positive effect on the reproductive number of COVID-19. This so-called R number indicates how many people an infected person infects on average.

According to the study, nighttime curfews can lower this value by 13%. The authors point out, however, that this has to be seen as part of a wider set of measures such as the closure of restaurants and restrictions on private meetings.

So far, the study has only been published as a preprint, so it has not yet been peer-reviewed.

Canada as a case study

Canadians have already gained experience with curfews in the past year. A nighttime curfew has been in effect in the province of Quebec in highly affected regions since the beginning of January.

When DW asked at the end of March what scientific basis the decision was based on and whether the effects of the measure would be evaluated, the provincial Health Ministry could not provide a definitive answer. However, it said, "observational studies show this measure prevents meetings."

The statement is supported by a preprint study published later by several Canadian scientists. It shows that nighttime mobility in Quebec was 31% lower than in neighboring Ontario, which has no curfew.

Jay Kaufman, an epidemiologist at McGill University in Montreal, Quebec's largest city, wrote to DW: "Quebec had stable or diminishing caseloads over most of the last few months, even while other Canadian provinces were increasing." Nevertheless, he cannot and does not want to attribute the developments solely to the curfews in Quebec, says Kaufman, who was not involved in the study.

Many other factors play a role — such as the vaccination rate, the number of tests per day, or whether lessons take place digitally or in school.

The number of cases has risen again, says Kaufman, after the beginning of the curfew in mid-March was postponed from 8 p.m. to 9:30 p.m. due to the changing of the clocks to summertime. "But how these various policies interact and what is the unique contribution of each one is something that would require a careful study, not merely a vague impression," says the epidemiologist.

Incidentally, anyone who is on the street at night for no good reason has to pay a fine of 1,000 to 6,000 Canadian dollars (around €670 to €4,400), young people have to pay a fine of $500.

Politics must be more transparent

In Germany, there has so far been a lack of data for a reliable study, says Professor Christof Schütte, president of the Zuse Institute Berlin, which works in the field of modeling and simulations. In his opinion, curfews can be very effective "if they are really observed together with the other measures," he told DW.

Schütte also sees politics as having an obligation to communicate more clearly and uniformly. But he fears that the effect will only last for a short time, as people would instead meet at different times of the day.

Simulation is like a computer game

Amineh Ghorbani believes that despite such meetings during the day, curfews would have an effect. Ghorbani teaches at the TU Delft in the Netherlands at the interface between computer-based social sciences and engineering. In her work, she uses simulations to study human behavior.

Together with scientists from France, the Netherlands, and Sweden, she has been working on the ASSOCC project, a simulation in which an artificial society is exposed to the coronavirus pandemic for a year. They are using them to test the effectiveness of various coronavirus measures and, according to their own information, have advised the Swedish and Italian governments.

This society is comparable to the computer game "The Sims," explains Ghorbani in an interview with DW. The people in the simulation have needs such as hunger or the desire to see friends. When the desires get very strong, it may mean that they start disobeying rules.

The result of the simulation: Curfews at night help prevent the number of infections from skyrocketing and can thus make a contribution to protecting the health system from being overburdened.

But Ghorbani also says that "unlike a full lockdown of two weeks where things seem to be working after that. Curfews need a more extended period to be effective." In addition, they are not as effective on their own and should therefore be combined with other measures.

How effective curfews are compared to other measures also depends on where you are in the pandemic. In Germany and the Netherlands, the numbers show a new wave of infections. "If you decide to go to a strict lockdown, it's good to have the curfew as well with a lockdown," explains Ghorbani, referring to the simulation. After three weeks, for example, the lockdown could be relaxed, but the curfews should remain in place in order to be able to keep the positive effect of the tough restrictions longer.

France's experience is not clear

Even in large parts of France, people have not been allowed to go out at night for months without a good reason. The curfews sometimes apply from 8 p.m., sometimes from 6 p.m., sometimes from 7 p.m.

Science does not fully agree on the effects of these restrictions. A group of scientists from Toulouse has found out that the nighttime curfews could have a negative effect: The curfews at 8 p.m. in Toulouse reduced the spread of the virus, but the curfews at 6 p.m. worsened the situation. The reason for this, according to the group, could be that more people gathered in supermarkets earlier.

A current preprint study by researchers at the French Institute for Health and Medical Research advocates night curfews in principle. Accordingly, they were helpful in curbing the spread of the original SARS-CoV-2 strand in January. However, according to the researchers, they, together with other so-called "social distancing" measures, were not sufficient to curb the spread of the more aggressive British mutant B.1.1.7.

Fact check: Anyone who uses or supports curfews as a measure in the coronavirus pandemic is happy to point out other countries that are already using them as evidence of their effectiveness. So far, however, the data is still sparse.

However, studies and simulations indicate that they can be quite effective under certain conditions — for example in combination with a lockdown or the restriction of private meetings.

This article was translated from German.