Epidemiology

Blastomycosis occurs within geographically limited regions of the US, Canada, Mediterranean basin, and South Africa.[1][2]​​​​​ Occasional cases are detected in Central and South America and the Middle East.[4][6][7]​​​​​​​​​ The incidence of blastomycosis in 2019 was 0.8 cases per 100,000 population in US states where it is a reportable condition, which include Arkansas, Louisiana, Michigan, Minnesota, and Wisconsin.[8][9]​​​ A 2023 epidemiological study found that counties in 40 US states exceeded the clinically relevant threshold for blastomycosis.[10]​​​​ Data suggest that blastomycosis may be endemic in the Northeastern region of the US.[11][12]​​​

In the Canadian provinces of Ontario and Manitoba, the annual incidence ranges from 0.29 cases per 100,000 population to as high as 7.11 cases per 100,000 in the Kenora, Ontario district.[13][14] Epidemiological trends reveal a tendency for infection to occur in middle-aged men who have occupational or recreational exposure to soil, wooded areas, or waterways.[15][16]

Blastomycosis has also been reported in all of South Africa.[17] Age and sex distribution are similar to the US, but the clinical manifestations are slightly different. South African patients tend to have more bone involvement and less central nervous system disease than patients in the US, and there is no apparent disease in dogs.[18] In the US, dogs and humans may simultaneously acquire the disease after exposure to the same environments, but a sick dog is a clue to exposure, rather than a vector for transmission of the disease to humans.

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