title: Influenza and pneumonia mortality in 66 large cities in the United States in years surrounding the 1918 pandemic.
abstract: The 1918 influenza pandemic was a major epidemiological event of the twentieth century resulting in at least twenty million deaths worldwide; however, despite its historical, epidemiological, and biological relevance, it remains poorly understood. Here we examine the relationship between annual pneumonia and influenza death rates in the pre-pandemic (1910-17) and pandemic (1918-20) periods and the scaling of mortality with latitude, longitude and population size, using data from 66 large cities of the United States. The mean pre-pandemic pneumonia death rates were highly associated with pneumonia death rates during the pandemic period (Spearman ρ = 0.64-0.72; P<0.001). By contrast, there was a weak correlation between pre-pandemic and pandemic influenza mortality rates. Pneumonia mortality rates partially explained influenza mortality rates in 1918 (ρ = 0.34, P = 0.005) but not during any other year. Pneumonia death counts followed a linear relationship with population size in all study years, suggesting that pneumonia death rates were homogeneous across the range of population sizes studied. By contrast, influenza death counts followed a power law relationship with a scaling exponent of ∼0.81 (95%CI: 0.71, 0.91) in 1918, suggesting that smaller cities experienced worst outcomes during the pandemic. A linear relationship was observed for all other years. Our study suggests that mortality associated with the 1918-20 influenza pandemic was in part predetermined by pre-pandemic pneumonia death rates in 66 large US cities, perhaps through the impact of the physical and social structure of each city. Smaller cities suffered a disproportionately high per capita influenza mortality burden than larger ones in 1918, while city size did not affect pneumonia mortality rates in the pre-pandemic and pandemic periods.
authors: Departamento de Microbiologia y Parasitologia, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México. acunasoto.rodolfo@gmail.com
authors: Rodolfo
authors: R
authors: Acuna-Soto
authors: Cécile
authors: C
authors: Viboud
authors: Gerardo
authors: G
authors: Chowell
mesh_terms: D002947:Cities / Q000706:statistics & numerical data*; D049673:History, 20th Century; D006801:Humans; D007251:Influenza, Human / Q000150:complications / Q000266:history* / Q000401:mortality*; D058873:Pandemics / Q000706:statistics & numerical data*; D011014:Pneumonia / Q000150:complications / Q000401:mortality*; D011156:Population Density; D011237:Predictive Value of Tests; D018709:Statistics, Nonparametric; D013997:Time Factors; D014481:United States / Q000453:epidemiology