Context: Recent increases in infectious disease mortality and concern about emerging infections warrant an examination of longer-term trends.

Objective: To describe trends in infectious disease mortality in the United States during the 20th century.

Design and setting: Descriptive study of infectious disease mortality in the United States. Deaths due to infectious diseases from 1900 to 1996 were tallied by using mortality tables. Trends in age-specific infectious disease mortality were examined by using age-specific death rates for 9 common infectious causes of death.

Subjects: Persons who died in the United States between 1900 and 1996.

Main outcome measures: Crude and age-adjusted mortality rates.

Results: Infectious disease mortality declined during the first 8 decades of the 20th century from 797 deaths per 100000 in 1900 to 36 deaths per 100000 in 1980. From 1981 to 1995, the mortality rate increased to a peak of 63 deaths per 100000 in 1995 and declined to 59 deaths per 100000 in 1996. The decline was interrupted by a sharp spike in mortality caused by the 1918 influenza epidemic. From 1938 to 1952, the decline was particularly rapid, with mortality decreasing 8.2% per year. Pneumonia and influenza were responsible for the largest number of infectious disease deaths throughout the century. Tuberculosis caused almost as many deaths as pneumonia and influenza early in the century, but tuberculosis mortality dropped off sharply after 1945. Infectious disease mortality increased in the 1980s and early 1990s in persons aged 25 years and older and was mainly due to the emergence of the acquired immunodeficiency syndrome (AIDS) in 25- to 64-year-olds and, to a lesser degree, to increases in pneumonia and influenza deaths among persons aged 65 years and older. There was considerable year-to-year variability in infectious disease mortality, especially for the youngest and oldest age groups.

Conclusions: Although most of the 20th century has been marked by declining infectious disease mortality, substantial year-to-year variation as well as recent increases emphasize the dynamic nature of infectious diseases and the need for preparedness to address them.