Many parallels are currently being drawn between the flu pandemic of 1918 and the modern spread of the coronavirus, including how a lockdown was imposed in many cities:

It happened a century ago, too.

On Oct. 5, 1918, Seattle Mayor Ole Hanson made a stunning announcement.

He ordered “every place of indoor public assemblage in Seattle, including schools, theatres, motion picture houses, churches and dance halls closed by noon” that day, a Seattle Daily Times story said.

But what was the purpose of these lockdowns? Medicine was rudimentary and couldn't do much to help against viral infections - not that we're much more effective in 2020, given our struggles with COVID-19. Attempts were made to develop vaccine, but authorities weren't able to produce enough injections to inoculate the entire population. Contact tracing would've been impossible given the lack of available tests. Given the above, is it known if the lockdown of 1918 was actually effective or did every American eventually become ill with the novel flu regardless of the lockdowns?

  • Yes, they were. I recently saw a documentary about it, but haven't bookmarked it.
    – Jos
    Apr 30, 2020 at 6:10
  • 3
    lack of basic research around plague law and history May 2, 2020 at 6:42

1 Answer 1


Denver, Colorado is a good sample of the results when the measures start early, but are revoked too soon.

The goal of the lockdown is to prevent people meeting and transferring the virus on to others.

When started early, less people are effected and don't pass it on.

On Armistice Day (1918-11-11), people gathered together to celebrate with the result that the virus was passed on to others.

During the next 11 days, those newly infected, passed it on to others until the measures were reinstated.

This is the effect when such measures start too late. More people are affected and they in turn pass it on to others.

Had the measures not have been revoked, the second 'hump' would not have occurred (the effected people on the 11th would not have passed it on had they remained isolated) .

  • 1918-09-27: first death
  • 1918-10-06: first bans
    • 1918-10-15: 1.440 cases
    • 1918-11-11: removed, including face masks
      • 1918-11-18: 100 cases daily
    • 1918-11-22: reinstated (25th face masks)
      • 6000 cases, 500 deaths
      • 1918-11-27: 438 new cases, 17 deaths
  • 1918-12-31: 12.718 influenza cases, 1.218 deaths

Denver double hump

St. Louis also imposed restrictions but did not revoke them for Armistice day: no second hump for that period. The restrictions were lifted on the 20th of December and reimposed 1 month later.

Philadelphia imposed no restrictions, which together with a higher, denser population caused the highest numbers of the US cities.

San Francisco, which was spared the first wave of spring of 1918, was aware of the problem but only reacted after the first cases became noticeable.

Deaths per 100.000 (above the expected usual death rate):

  • New York 452
  • St. Louis 356
  • Denver 631
  • San Francisco 672
  • Philadelphia 748

2020-04-29: 10 days into a relaxed shutdown

  • Active cases: 21.46% of total cases (6 weeks into lockdown)
    • 2020-04-06: 70.49% of total cases (3 weeks into lockdown)

A major difference to 1918 is that a social distance and encouraged usage of face masks requirements are still in place.

Germany, 2020-04-30


  • But... how could the Spanish flu have possibly died out without reaching herd immunity? Did the US really eliminate it altogether? Didn't the cities that imposed a lockdown see an equivalent number of deaths, but over a longer period of time? Apr 30, 2020 at 6:32
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    @JonathanReez There were reoccurring waves during the early 1920's (worldwide). Research results around the 2000's suggest that the virus mutated into a less deadly form. Unfortunately at that time collection of research data was neglected, so proper conclusions today are difficult. Apr 30, 2020 at 6:39
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    @JonathanReez - When the R0 is less than one, an infection will peter out. Some cities took social distancing measures that reduced R0 enough (at least in the summer months, when flu transmits less readily) that the infection stopped before herd immunity. Philadelphia got herd immunity quickly, but at a terrible death toll.
    – antlersoft
    Apr 30, 2020 at 13:43
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    @Joe but that's just speculation, right? Wouldn't the default position be that the 1918 flu infected 80+% of Americans, meaning that all restrictions in 1918 were futile? May 1, 2020 at 22:29
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    @MarkJohnson but how do we know that the total number of deaths in Denver per capita wasn't exactly equal to the total number of deaths in other major cities? As for managing the disease - did medicine in 1918 actually save anyone? As in, did mortality increase in cities where there were too many patients? That's non-trivial to confirm in 2020, but do we know if Spanish flu treatments had any effectiveness whatsoever in 1918? May 2, 2020 at 5:01

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