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Open Access Publications from the University of California

Influenza as a proportion of pneumonia mortality: United States, 1959-2009


As causes of death, influenza and pneumonia are typically analyzed together. We quantify influenza’s contribution to the combined pneumonia and influenza mortality time series for the United States, 1959–2009. A key statistic is I/(P+I), the proportion of pneumonia and influenza mortality accounted for by influenza. Year-to-year, I/(P+I) is highly variable and shows long-term decline. Extreme values of I/(P+I) are associated with extreme P+I death rates and vice-versa, but I/(P+I) is a weak predictor of P+I mortality overall. Prominence of influenza in the medical news is associated with high I/(P+I). Influenza and pneumonia should be analyzed as a combined cause.

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