Public health interventions and epidemic intensity during the 1918 influenza pandemic

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 18; pp. 7582 - 7587
• Main Authors: Hatchett, Richard J, Mecher, Carter E, Lipsitch, Marc
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 01-05-2007; National Acad Sciences
• Series: From the Cover
• Subjects: Biological Sciences; Churches; Cities; Disease Outbreaks - history; Disease Outbreaks - prevention & control; Disease transmission; Epidemics; History, 20th Century; Humans; Infections; Influenza; Influenza A Virus, H1N1 Subtype; Influenza, Human - epidemiology; Influenza, Human - history; Influenza, Human - prevention & control; Influenza, Human - transmission; Intervention; Mortality; Notifiable diseases; Pandemics; Psychoeducational intervention; Public health; Public Health - history; Sensitivity and Specificity; Time Factors; United States - epidemiology; United States
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0610941104

Nonpharmaceutical interventions (NPIs) intended to reduce infectious contacts between persons form an integral part of plans to mitigate the impact of the next influenza pandemic. Although the potential benefits of NPIs are supported by mathematical models, the historical evidence for the impact of such interventions in past pandemics has not been systematically examined. We obtained data on the timing of 19 classes of NPI in 17 U.S. cities during the 1918 pandemic and tested the hypothesis that early implementation of multiple interventions was associated with reduced disease transmission. Consistent with this hypothesis, cities in which multiple interventions were implemented at an early phase of the epidemic had peak death rates [almost equal to]50% lower than those that did not and had less-steep epidemic curves. Cities in which multiple interventions were implemented at an early phase of the epidemic also showed a trend toward lower cumulative excess mortality, but the difference was smaller ([almost equal to]20%) and less statistically significant than that for peak death rates. This finding was not unexpected, given that few cities maintained NPIs longer than 6 weeks in 1918. Early implementation of certain interventions, including closure of schools, churches, and theaters, was associated with lower peak death rates, but no single intervention showed an association with improved aggregate outcomes for the 1918 phase of the pandemic. These findings support the hypothesis that rapid implementation of multiple NPIs can significantly reduce influenza transmission, but that viral spread will be renewed upon relaxation of such measures.