Increased prevalence of fungal infections in the United States

Increased prevalence of fungal infections in the United States

Several species of fungi, including members of the genera Histoplasma, Coccidioides, and Blastomyces, are endemic to various areas of the United States. In the past, the geographic distribution of both Histoplasma and Coccidioides was attributed to positive antigen skin test results, while that of Blastomyces was based on case and outbreak reports.

Over the past fifty years, an increasing number of fungal infections due to these various species have recently been reported outside of their endemic regions in the United States Clinical infectious disease Study, researchers update the geographic distribution of these species in the United States

Learn: The geographic distribution of dimorphic mycoses in the United States for the modern era. Photo credit: sruilk / Shutterstock.com

About studying

The current study used geographic data obtained from Medicare Feed-for-Service (FFS) claims from individuals aged 65 years and older between 2007 and 2016. Diagnosis of infection with Histoplasma, Coccidioides, or Blastomyces was made using the International Classification of Diseases, 9th Edition (ICD-9) and ICD-10 diagnosis codes.

The primary outcome of the study was the number of reported cases per 100,000 person-years (PY). The incidence of infection with each fungal species was determined by dividing the number of individuals diagnosed with the infection by the available PY of Medicare FFS beneficiaries for each year and then summing as a 10-year total.

Incidence rates of fungal infections were also mapped for each county in the United States

Study results

Between 2007 and 2016, a total of 79,749 histoplasmosis, 37,726 coccidioidomycosis and 6,109 blastomycosis cases were reported.

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Of a total of 3,143 U.S. counties, 1,971 reported more than five histoplasmosis diagnoses. Notably, 92% of these countries had an incidence greater than 100/100,000 PY.

A total of 839 counties reported more than three coccidioidomycosis diagnoses, 40% of which had an incidence greater than 100/100,000 PY. In the 1,602 counties with more than one blastomycosis diagnosis, 24% had an incidence greater than 50/100,000 PY.

Notably, at least one county in 48, 35, and 30 states, including Washington DC, was above the incidence threshold for histoplasmosis, coccidioidomycosis, and blastomycosis, respectively. Taken together, these incidence rates significantly exceeded the limits previously described in 1969.

Effects

Diagnosis of blastomycosis and coccidioidomycosis is delayed for more than a month in 40% and 46% of cases, respectively. A similarly high diagnostic delay of 40 days has been reported for histoplasmosis. Therefore, the huge increase in prevalence of the three fungal infections examined in the current study highlights the importance of their detection to avoid delays in diagnosis, particularly in immunocompromised individuals.

Although the fungal species evaluated in the current study were specific to the United States, they are also found in several countries around the world. More specifically, Histoplasma is found on all continents except Antarctica, while Coccidioides is found in both North and South America, and Blastomyces is found in North America, Africa, and Asia.

Several factors likely contributed to the increased prevalence of these fungal species in the United States, of which travel-related exposure is likely the largest factor. In addition to travel, anthropogenic climate change and changing land development practices may also increase infection rates in new areas.

Nevertheless, further research is needed to better understand the extent to which these factors contribute to the widespread distribution of these fungal species in the United States and to identify their soil reservoirs in these locations.

“Recognition of expanded geographic distributions for [DM] diagnoses is important to maintain high clinical suspicion for these pathogens.”

Reference:

• Mazi, PB, Sahrmann, JM, Olsen, MA, et al. (2022). Die geografische Verbreitung dimorpher Mykosen in den Vereinigten Staaten für die Neuzeit. Klinische Infektionskrankheiten. doi:10.1093/cid/ciac882.

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