A rare but potentially fatal fungal disease may be endemic in a wider area than previously thought, according to a paper yesterday in Emerging Infectious Diseases.
The disease, blastomycosis, is caused by the environmental fungus Blastomyces, which is found in moist soil and decaying organic matter. While most people who breath in spores don't get sick, the fungus can cause pneumonia-like symptoms and result in severe illness, with death rates as high as 22%.
Based on sporadic case reports and documented outbreaks, blastomycosis has historically been considered endemic in states along the Ohio and Mississippi rivers, the Great Lakes, and the St. Lawrence Seaway, with annual incidence rates in those areas estimated to range from 0.2 to 2.0 cases per 100,000 persons. Public health surveillance is limited to Arkansas, Louisiana, Minnesota, Michigan, and Wisconsin.
Elevated incidence in Vermont
But based on recent evidence suggesting that incidence in the Northeast may be greater than known, researchers with the Centers for Disease Control and Prevention and the Vermont Department of Health examined data from the state's all-payer health insurance claims to identify blastomycosis diagnoses. They identified 114 patients (median age 55, 59% male) diagnosed with blastomycosis from 2011 through 2020.
The mean annual statewide incidence of 1.8 cases/100,00 persons is greater than the mean annual incidences in four of the five states that mandate reporting from 1987 through 2017, and higher than reported in other states (Missouri, Mississippi, and Illinois) located in know endemic areas.
"Although differences in surveillance methods and case definitions among states make direct comparisons difficult, Vermont's burden of blastomycosis appears comparable to, and perhaps higher than, most states that have published blastomycosis incidences," the study authors wrote.
Of the 114 patients diagnosed, 30 had one or more blastomycosis-related hospitalization, and 4 died from the infection. Nearly half of the case-patients and 65% of hospitalized patients lived in three counties in the north-central part of the state (Lamoille, Orleans, and Washington counties).
Expanded surveillance needed
The authors note that, like hyperendemic regions of Wisconsin, Vermont is rich in acidic spodosol soil, which is thought to support Blastomyces growth. They say clinicians should consider blastomycosis in patients with compatible signs and symptoms, and that expanded surveillance is needed.
"Our findings, based on the most comprehensive assessment of blastomycosis in Vermont to date, align with a growing body of evidence suggesting that the burden of endemic blastomycosis is greater than commonly appreciated," they concluded. "These results challenge routine assumptions about the epidemiology and ecology of this disease and reflect a need for future studies."
Our findings, based on the most comprehensive assessment of blastomycosis in Vermont to date, align with a growing body of evidence suggesting that the burden of endemic blastomycosis is greater than commonly appreciated.
