• Do partial (e.g., nighttime) curfews curb the spread of epidemics?
  • What is the (epidemiological) mechanism by which partial curfews curb the spread of epidemics?
  • Is there evidence from past or present pandemics that this works?

Related questions

  • This question in SE:MedicalSciences asked about nightly curfews 8 months ago, but with a focus on economic and other effects. It cited evidence that curfews failed for economic reasons during Ebola outbreaks. It did not elaborate why limiting the time everyone can go to a shop would magically lead to less many people being in the shop at the same time. The only (non-accepted) answer to the question is speculative and concludes that the author is not sure if curfews are effective.
  • The same question was cross-posted here in SE:Biology and closed for that reason (cross-posting). There appear to have been some comments but these were deleted when the question was closed.

Related Research

The only papers on the topic i could find are two papers in the context of the Ebola epidemic in Liberia in 2014/2015. Both papers unfortunately focus on public health policy and not on the epidemiological merits of the measure:

The standard SIR- (and SIS-, SEIR-, ...)-Models predict a reduction of the infection rates when social interactions are reduced. This is obvious and not in doubt. Some common infection prevention measures (working from home, suspension of inter-regional travel, social distancing, restriction of contacts between households, closure of social gathering places) are designed to do this. In the case of partial curfews, it is not clear to me, if this (reduction of social interactions) is the objective and by what epidemiological mechanism that objective (reduction of social interactions) is meant to be achieved with partial curfews.

Why would a nighttime curfew not curb (possibly increase) the spread of the epidemic

People are still allowed (and will still) go to shops, do exercise etc., but if they have to do it at specific times, they are more likely to bump into each other. Human nature may even cause people to congregate in shops just before the curfew time (because you realized that you're out of pasta or so). So this might actually make it easier for the virus to spread.

Why would a nighttime curfew curb the spread of an epidemic

I am not sure; this is why I'm asking.

Some very far-fetched possibilities I could think of:

  • Making illegal gatherings inconvenient while being easy to enforce?
  • Reducing service personnel working away from home?
  • Forcing people to stick to the regular workday sleep cycle even while staying at home to prevent mental health issues which would lead to more people attending hospitals?

Context (Why is this relevant?)

Several countries have declared night-time curfews or are considering these to tackle the current wave of Covid-19 outbreaks. This includes, among many other countries, France, Germany, Spain, Hungary, Tunisia, South Africa.

For some measures, the objectives are clear and obvious: social distancing, closure of restaurants, bars, workplaces, schools etc., self-isolation of infected people and their contacts, face masks, vaccination, etc. Last year Spain took this policy to the extreme by assigning specific time slots to specific demographic groups.

However, I do not understand what good nighttime curfews would do - or other part-time curfews for that matter - unless the curfew is complete, 24 hours a day every day (i.e., everyone except for essential personnel locked in their homes, like in Hubei in early 2020).

To be clear:

  • I do not dispute that limiting social interactions helps.
  • It is easy to see that a full (24 hour every day) curfew should effectively halt the spread.
  • I am not asking about effects on mental health or on the economy.
  • I am specifically asking about the epidemiological rationale behind imposing nighttime curfews.

Edit (Jan 29 2021), note regarding the Covid-19 curfew in the Netherlands in on January 23 2021.: The Dutch government claims "Research has shown that night-time curfews help to reduce the spread of the virus." This suggests that there is scientific evidence, but they do not detail what evidence that is, what the underlying epidemiological mechanism is, or where it can be found and reviewed. They only add that the Dutch curfew between 9pm and 4.30am "will prevent people from visiting each other and gathering in groups". At the same time, "visiting each other" remains explicitly permitted in the Netherlands during day-time, although for only one visitor at a time. (Yes, the Dutch curfew is the one to which some violent Neonazis and Antisemites in the Netherlands responded by rioting and looting. I would like to point out that the Dutch curfew and the riots etc happened only after I asked this question and that I have no sympathy for those responsible, although I would still like to understand how exactly night-time curfews are supposed to help.)

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    $\begingroup$ @David This answer on SE:Biology Meta suggests that epidemiology is on topic here. While you may argue that restrictions such as curfews are unrelated to epidemiology, I specifically asked about the merits of a specific policy from an epidemiological perspective. Also, there was a similar question earlier (linked in the OP) that was closed not for being off-topic but for being cross-posted. If everyone agrees with David, please go ahead and close or delete. But I have to admit, I am a bit shocked by the level of anger in David's comment. $\endgroup$
    – 0range
    Jan 16 at 3:49
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    $\begingroup$ I don't speak for David, but do share his frustration that many of the posts in this site are completely inappropriate and often seem to involve no thought on the part of the poster. He may seem harsh, but he is not attacking you personally. Your post does have on-topic parts. but you've buried them in questions about intentions (e.g. the title). I encourage you to rewrite to focus on a single concise biological question. The tour, How to Ask, and other help center pages for more details on what is expected. $\endgroup$
    – tyersome
    Jan 16 at 6:54
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    $\begingroup$ @tyersome Thank you. I tried to rewrite the question to focus it on the epidemiological question. I am sorry that people are frustrated about many off-topic and inappropriate posts. But may I just reiterate (MattDMo said that yesterday) that the tour and how-to-ask do not state to a lot of detail what is or isn't on topic. I looked it up on SE: Biology Meta (see link above) and posted believing that what I was asking was actually on topic. $\endgroup$
    – 0range
    Jan 16 at 18:44
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    $\begingroup$ I think Skeptics.SE would likely take up the specific claim by the Dutch government. I think the biology side of the epidemiological question here is pretty superficial. The intent of the curfew is to reduce contacts between people, particularly contacts between people who are not already in contact at other times of the day (like family members). This is pretty obvious and has little to do with any underlying biology. The extent to which it is truly effective seems like a different question that isn't itself related to biology. $\endgroup$
    – Bryan Krause
    Jan 29 at 20:51
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    $\begingroup$ I'd add that I don't think the rationale for the specific policy is epidemiological, but that the policy makers agree: "limiting social interactions helps." Their goal is to make this happen with as little impact as possible, which is a political and economic calculation. $\endgroup$
    – Bryan Krause
    Jan 29 at 21:00