Nonpharmaceutical interventions implemented by US cities during the 1918-1919 influenza pandemic.
BACKGROUND
A critical question in pandemic influenza planning is the role nonpharmaceutical interventions might play in delaying the temporal effects of a pandemic, reducing the overall and peak attack rate, and reducing the number of cumulative deaths. Such measures could potentially provide valuable time for pandemic-strain vaccine and antiviral medication production and distribution. Optimally, appropriate implementation of nonpharmaceutical interventions would decrease the burden on health care services and critical infrastructure.


OBJECTIVE
To examine the implementation of nonpharmaceutical interventions for epidemic mitigation in 43 cities in the continental United States from September 8, 1918, through February 22, 1919, and to determine whether city-to-city variation in mortality was associated with the timing, duration, and combination of nonpharmaceutical interventions; altered population susceptibility associated with prior pandemic waves; age and sex distribution; and population size and density.


METHODS
Historical archival research, and statistical and epidemiological analyses. Nonpharmaceutical interventions were grouped into 3 major categories: school closure; cancellation of public gatherings; and isolation and quarantine.


METHODS
Weekly excess death rate (EDR); time from the activation of nonpharmaceutical interventions to the first peak EDR; the first peak weekly EDR; and cumulative EDR during the entire 24-week study period.


RESULTS
There were 115,340 excess pneumonia and influenza deaths (EDR, 500/100,000 population) in the 43 cities during the 24 weeks analyzed. Every city adopted at least 1 of the 3 major categories of nonpharmaceutical interventions. School closure and public gathering bans activated concurrently represented the most common combination implemented in 34 cities (79%); this combination had a median duration of 4 weeks (range, 1-10 weeks) and was significantly associated with reductions in weekly EDR. The cities that implemented nonpharmaceutical interventions earlier had greater delays in reaching peak mortality (Spearman r = -0.74, P < .001), lower peak mortality rates (Spearman r = 0.31, P = .02), and lower total mortality (Spearman r = 0.37, P = .008). There was a statistically significant association between increased duration of nonpharmaceutical interventions and a reduced total mortality burden (Spearman r = -0.39, P = .005).


CONCLUSIONS
These findings demonstrate a strong association between early, sustained, and layered application of nonpharmaceutical interventions and mitigating the consequences of the 1918-1919 influenza pandemic in the United States. In planning for future severe influenza pandemics, nonpharmaceutical interventions should be considered for inclusion as companion measures to developing effective vaccines and medications for prophylaxis and treatment.
Center for the History of Medicine, University of Michigan Medical School, Ann Arbor, USA.
Howard
H
Markel
Harvey B
HB
Lipman
J Alexander
JA
Navarro
Alexandra
A
Sloan
Joseph R
JR
Michalsen
Alexandra Minna
AM
Stern
Martin S
MS
Cetron
D000704:Analysis of Variance; D003140:Communicable Disease Control / Q000266:history* / Q000379:methods*; D004196:Disease Outbreaks / Q000266:history* / Q000517:prevention & control; D049673:History, 20th Century; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000266:history* / Q000401:mortality / Q000628:therapy*; D010356:Patient Isolation; D011634:Public Health; D011790:Quarantine; D012574:Schools; D018709:Statistics, Nonparametric; D014481:United States / Q000453:epidemiology; D014504:Urban Health / Q000266:history* / Q000706:statistics & numerical data; D014505:Urban Population / Q000706:statistics & numerical data