Researchers Highlight Trends in Infectious Disease Mortality in the US

Researchers at the University of Arizona (UA) in Tucson have highlighted some important trends regarding infectious disease mortality in the United States—perhaps quelling some of the media-fueled hysteria surrounding these bugs.

In a research letter published online on November 22^nd by the Journal of the American Medical Association, epidemiologists from the Mel and Enid Zuckerman College of Public Health at UA analyzed mortality data from the US National Office of Vital Statistics for the period of 1900-1967 and from the Centers for Disease Control and Prevention (CDC) for the period of 1968-2014 to capture and contextualize trends in infectious disease mortality from 1980-2014. Somewhat surprisingly, they found that infectious diseases accounted for a relatively small proportion of US mortality from 1980 through 2014, with pneumonia and influenza accounting for a large amount of those deaths, in spite of the introduction of new viruses, such as HIV/AIDS and West Nile virus, during that time period.

“There are two messages I see in this analysis,” study co-author Heidi E. Brown, PhD, told Contagion. “The first is the power of public health and capacity to respond to infectious disease threats. You can map major public heath milestones to… germ theory and improvements in sanitation, discovery of antibiotics, [and the introduction of] antiretrovirals in response to HIV/AIDS, etc. The second: This analysis shows the continued vulnerability to new disease introductions, such as HIV/AIDS and West Nile virus disease, and the future challenges we may face with changing patterns of pathogen resistance. These messages of new vulnerabilities are overlaid on diseases we are more familiar with, such as influenza, pneumonia, and vaccine preventable diseases, which continue to be a burden on the health of Americans.”

Indeed, the authors found in their analysis that infectious disease-related mortality decreased from the year 1900 to 1950, except for a “spike” that occurred during the 1918-1919 Spanish influenza pandemic, before leveling off. In all, infectious diseases were the cause of 5.4% of all deaths in the United States between 1980 and 2014, with an average annual percentage change of 0.4%, due in large part to a significant increase in mortality from 42 per 100,000 population to 63.5 per 100,000 population that corresponded with the HIV/AIDS epidemic from 1980 through 1995. Not surprisingly, the authors noted that HIV/AIDS mortality began to decline in 1995, when antiretroviral therapy was introduced.

According to the final report, most infectious disease deaths (38.3%) were attributed to influenza or pneumonia. Notably, in the age of the Zika virus, mean vector-borne disease mortality increased from 0.01 per 100,000 population in 1980 (when spotted fever was most common) to 0.05 per 100,000 population in 2002, when West Nile came to US shores.

On the positive side, vaccine-preventable disease death rates have fallen since 1980, to 0.8 per 100,000 population for Streptococcus pneumoniae infection. However, mortality due to drug-resistant pathogens has remained stable since 1980 (approximately 4.0 per 100,000 population), while mortality due to Clostridium difficile increased from 0.004 per 100,000 population to 2.4 per 100,000 population in 2007.

“This being mortality data, rather than morbidity, the trends tracked well with what we know to be important infectious diseases in the US,” Dr. Brown said. “We selected the disease groups based on burden and they showed some interesting trends—for example, the relative stable trend in influenza and pneumonia, the introduction of West Nile virus, and the challenges of antimicrobial resistance.”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.