Several countries around the world have instituted extremely harsh lockdowns: France, Spain, Italy, New Zealand, Argentina. However for some reason all of those countries keep getting new infections 2+ weeks after the lockdowns have started, which suggests gaps in their enforcement or coverage. Has there been any research done in these countries to try and understand where these cases are coming from? Some ideas:

  1. It's all from essential workers and their families
  2. It's from neighbors hanging out with each other - either voluntarily or involuntarily (elevators, stairs, common areas)
  3. It's from supermarkets, hospitals and pharmacies
  4. It's from people who are outside the "system", such as the homeless

Seems like contact tracing/interviews should give a straightforward enough answer, so did any government try to investigate?

  • 1
    Idea #5: Not respecting the lockdown. 20minutes.fr/paris/… Apr 13, 2020 at 9:56
  • Basically, most underestimate how severe the Chinese lockdowns and internal travel bans were in comparison to anything done elsewhere. So when you expect results like China's from "lockdown lite"... not gonna happen. Exponentials are a b*tch. science.sciencemag.org/content/early/2020/03/30/science.abb6105 (I should probably get back to typing my answer to your other recent question, I wrote about half ... then got distracted by variolation thing.)
    – Fizz
    Apr 13, 2020 at 10:28
  • There has been a lot of talk about the homeless but remember it is the relatively wealthy people who have more financial means to spread this around, and of course that has been the case so far: air travel, damnable cruises, private parties, beach vacations and so on.
    – Gordon
    Apr 13, 2020 at 15:33
  • The daily confirmed cases in Italy and Spain seem to be decreasing. I don't think anyone expected an immediate halt. Neither country is doing comprehensive contact tracing yet. Here is a project that "aims to track and compare policy responses around the world, rigorously and consistently" bsg.ox.ac.uk/research/research-projects/…. Another risk is care homes for the elderly.
    – Lag
    Apr 15, 2020 at 14:26

2 Answers 2


Very partial answer, from the South Korean experience:

The rapid spread of COVID-19 in South Korea has been attributed to one case linked to a superspreading event that has led to more than 3900 secondary cases stemming from church services in the city of Daegu (Kuhn, 2020; Ryall, 2020). This has led to sustained transmission chains of COVID-19, with 55% of the cases associated with the church cluster in Daegu (Bostock, 2020).

Moreover, three other clusters have been reported, including one set in Chundo Daenam hospital in Chungdo-gun, Gyeongsanggbuk-do (118 cases), one set in the gym in Cheonan, Chungcheongnam-do (92 cases), and one Pilgrimage to Israel cluster in Gyeongsanggbuk-do (49 cases). These few clusters have become the primary driving force of the infection.

The paper has more details on each cluster.

Similar patterns of large gatherings followed by spreading in families have been reported elsewhere, e.g. France and Italy. But most such studies published insofar focus on the early days of the pandemic, before the lockdowns were imposed.

Alas, for a more topical answer, it depends what one means by "hardcore" lockdowns. There is one such study being conducted in the German hotspot in Heinsberg. Insofar there have been only press interviews with the investigators, like

Instead, claims Streeck, his study found that: "There is no significant risk of catching the disease when you go shopping. Severe outbreaks of the infection were always a result of people being closer together over a longer period of time."

And as a reminder for what "hardcore" lockdowns actually means:

During the height of the lockdown, Wuhan residents were completely barred from stepping outside of their home, not even allowed to go grocery shopping and they were consequently completely reliant on designated neighborhood committees who delivered daily necessities to them.

Basically more or less home arrest for almost everyone.

  • 1
    The German study is interesting, looking forward to the final results. Apr 13, 2020 at 15:39

New Zealand is undertaking rigorous contact tracing and so far only 2% of cases have been deemed community transmission meaning no known contact.

Cases have been increasing because they include disease developing in those returning to the country during the lockdown period and placed into self isolation. As the numbers of people returning to New Zealand fall so do these new imported cases.

These new cases are still within the numbers predicted by modelling.

NZ moved to level 4 lockdown 25 March which means stay at home unless essential service.

The other source are 4-5 larger clusters where one person has spread the disease to a number of others, and then these others have brought the disease back home. This also includes rest homes for the elderly and dementia units where either a visitor or staff before the lockdown had infected a resident, and the disease is still slowly spreading through these communities. At present we have a total of 16 clusters of 10 or more people infected.

We are still testing below capacity but increasing testing has failed to find more cases in the community that were not related to a known cluster.


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