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In the United States, it has mostly plagued humans and animals in Arizona and California’s San Joaquin Valley, where the illness was first described as “San Joaquin Valley fever” more than a century ago.

Indeed, the name valley fever is a shorter and more general term for an earlier name, San Joaquin Valley fever, because it was so common in that part of California.

It soon became known as the San Joaquin Valley Fever, such was its prevalence there but by the 1940s, its existence in Arizona was well documented.