Researchers discover two serious fungal diseases well outside of previous range

A research collaboration between UC Berkeley School of Public Health and University of Michigan scientists has found that two serious fungal diseases, blastomycosis and histoplasmosis, are no longer confined to their traditional endemic regions in the United States.

The diseases are caused by breathing in infectious fungal spores that live in the environment, and while many infections are asymptomatic or mild, severe disease can occur even among previously healthy individuals. The researchers found that cases have doubled over the past decade, with a significant increase in diagnoses appearing in new states.

The diseases have long been considered endemic—meaning they are consistently present—to the Mississippi and Ohio River Valleys, where they cause substantial ill health and more than $230 million in costs to healthcare systems per year. Researchers from UC Berkeley, the University of Michigan, Children’s Mercy Research Institute, and the University of Missouri-Kansas City leveraged a large, nationally representative electronic health record database to examine how the two fungal diseases are changing in the United States.

Published in the Journal of Infectious Diseases, the study found that incidence rates of the two diseases across the U.S. have doubled from 2013 to 2023.

While certain areas like the Upper Midwest and Ohio Valley had consistently high incidence, the data revealed new and unexpected areas of high risk. “We found high incidence of the diseases in areas that do not report surveillance data to the Centers for Disease Control and Prevention (CDC), such as high rates of blastomycosis in Illinois, Kentucky, and West Virginia, and of histoplasmosis in Missouri, Iowa, and Oklahoma,” said lead author Juliana Bartels, MPH, who is currently a Cal-EIS fellow, but was previously a graduate student researcher at UC Berkeley, where she worked on the research presented in this study. “Our findings argue for expanded reporting of these diseases so that we can better understand their geographic distribution and develop strategies improving clinician and popular awareness of the risk of contracting these diseases.”

Because early diagnosis leads to earlier treatment and better outcomes, we need to better understand where these fungal diseases are affecting people. “Histoplasmosis and blastomycosis are often diagnosed late, if at all, because they look like bacterial pneumonia or other diseases,” said Professor Jennifer R. Head of the University of Michigan, senior author of the study. Head received her PhD in Epidemiology at UC Berkeley School of Public Health in 2022. “If physicians don’t realize that their state could be endemic for these diseases, they are unlikely to consider testing for fungal pathogens. Blastomycosis responds well to antifungal treatment, yet can have high mortality rates if untreated.”

The study is one of the largest of its kind, providing an updated and comprehensive look at the epidemiology of these diseases by race and ethnicity, age group, and gender in the U.S.

While a typical blastomycosis patient has tended to be a young, white male who recreates or works outdoors, the researchers found that, from 2013 to 2023, incidence rates of blastomycosis were 60% higher among Hispanic or Latino patients than the national incidence rate, and 30% higher among non-Hispanic Black patients. Both diseases had elevated incidence rates among males and older age groups.

“We need to understand what is behind the differences in clinical presentation and disease severity among these groups, and to re-examine profiles of “typical” patients of these diseases,” said UC Berkeley School of Public Health Professor Justin V. Remais, who co-authored the study. “Future research can build on this research to examine how changes in travel, prevalence of immunosuppression, diagnostic awareness, and environmental factors like temperature and precipitation are contributing to the changing epidemiology of these diseases.”