Nonpharmaceutical Interventions Implemented by US Cities During the 1918-1919 Influenza Pandemic

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).