Infectious Disease Mortality Trends in the United States, 1980-2014

From 1900 through 1996, mortality from infectious diseases declined in the United States, except for a 1918 spike due to the Spanish flu pandemic.¹ Since 1996, major changes in infectious diseases have occurred, such as the introduction of human immunodeficiency virus (HIV)/AIDS and West Nile virus into the United States, advances in HIV/AIDS treatment, changes in vaccine perceptions, and increased concern over drug-resistant pathogens. We investigated trends in infectious disease mortality from 1980 through 2014 to capture these changes.

Using International Classification of Diseases codes, overall and infectious disease mortality data were extracted, based on underlying causes of death, from the National Office of Vital Statistics reports from 1900 through 1967 and from the Centers for Disease Control and Prevention (CDC) WONDER database from 1968 through 2014.² The University of Arizona determined the study was exempt from review.

Crude mortality rates for infectious and noninfectious causes (per 100 000 population) from 1900 through 2014 were graphed along with selected infections from 1980 through 2014 based on overall burden (influenza, pneumonia) and emergence or reemergence (HIV/AIDS, vector-borne diseases, vaccine-preventable diseases, drug-resistant pathogens). Vaccine-preventable diseases included those for which vaccines are routinely provided in the United States. Pathogens with drug resistance were identified based on classification by the CDC.³ Average annual percentage change (AAPC) was calculated using a 2-sided permutation test. Joinpoint Trend Analysis Software (National Cancer Institute), version 4.2.0,⁴ was used to create a weighted regression of the time series. Segments were selected based on statistical significance (2-sided P < .05) except for HIV/AIDS (which was manually given a joinpoint in 1995 to capture the peak of the epidemic and AAPCs calculated before and after 1995) and vector-borne diseases (for which interannual variability made trend analysis inappropriate).

Overall and infectious disease mortality decreased from 1900 through 1950 (except for the 1918 spike) and then leveled off (Figure, A).

From 1980 through 2014, infectious diseases composed 5.4% (95% CI, 5.1% to 5.8%) of overall mortality. Per 100 000 population, infectious disease mortality increased from 42.0 in 1980 to 63.5 in 1995, paralleling trends in HIV/AIDS mortality. A decline in overall and HIV/AIDS mortality in 1995 was associated with the introduction of antiretroviral therapy (Figure, B). The overall AAPC was 0.4 (95% CI, −0.4 to 1.2) from 1980 through 2014.

Most infectious disease deaths (38.3% [95% CI, 37.1%-39.4%]) from 1980 through 2014 were due to influenza or pneumonia (Figure, B and Table).

Prior to the introduction of West Nile virus (1980-1999), mean vector-borne disease mortality was 0.01 per 100 000 population (95% CI, 0.01-0.02); primarily from spotted fevers (Figure, C). Since 2002, the mean rate was 0.05 per 100 000 population (95% CI, 0.04-0.06).

Vaccine-preventable disease death rates decreased since 1980 (Figure, D and Table). In 2014, the rate was 0.8 per 100 000 population for Streptococcus pneumoniae infection. Mortality due to hepatitis B alone showed an increase coincident with the HIV/AIDS epidemic (per 100 000 population: 0.13 in 1980 and 0.39 in 1995).

Mortality due to pathogens with drug-resistant strains remained stable since 1980 at about 4.0 per 100 000 population (95% CI, 3.80-4.13) (Figure, E and Table). Mortality from Clostridium difficile, a hospital-acquired infection with drug resistance, increased from almost none in 1989 (n = 74 deaths; 0.004 per 100 000 population) until reaching a plateau since 2007 (2.4 per 100 000 population [95% CI, 2.3-2.5]).

Infectious diseases represented a small proportion of overall US mortality from 1980 through 2014, with influenza or pneumonia accounting for approximately 40% of infectious disease mortality. Major changes in mortality from HIV/AIDS, West Nile virus, and C difficile occurred over this period. Mortality due to vaccine-preventable diseases declined, whereas mortality due to pathogens with resistant strains remained stable.

The study is limited to US mortality reported on death certificates, only partly capturing the true burden of these diseases. Globally, infectious diseases were the second (lower respiratory infections), fourth (diarrheal diseases) and fifth (HIV/AIDS) leading causes of lost disability-adjusted life-years.⁵

Grouping related diseases (eg, vector-borne disease) and using national-level data allow for the evaluation of general trends. However, trends in population subgroups and at the community level, such as measles outbreaks within low-vaccination communities, were not captured. Nonetheless, these trends illustrate the continued US vulnerability to infectious diseases.

Corresponding Author: Heidi E. Brown, PhD, Mel and Enid Zuckerman College of Public Health, Department of Epidemiology and Biostatistics, University of Arizona, 1295 N Martin Ave, Tucson, AZ 85724 (heidibrown@email.arizona.edu).

Author Contributions: Dr Brown and Ms Hansen had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Hansen, Oren, Brown.

Acquisition, analysis, or interpretation of data: All Authors.

Drafting of the manuscript: All Authors.

Critical revision of the manuscript for important intellectual content: Oren, Dennis, Brown.

Statistical analysis: All Authors.

Administrative, technical, or material support: Oren, Brown.

Study supervision: Oren, Brown.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Additional Contributions: We thank Sharia Smith, BS (University of Arizona), who performed preliminary analyses using mortality data for the Arizona-Mexico border. She received no compensation for her contribution.