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Science and Innovations

Valley Fever Originated in Arizona

Arthroconidia_of_Coccidioides_immitis_credit-CDC.jpg
CDC
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Valley Fever is named for California’s San Joaquin Valley, but the fungus that causes the disease actually originated in Arizona. That finding is the result of genetic testing performed by Flagstaff scientists.

Scientists at the Translational Genomics Research Institute tracked the origins of Valley Fever with genetic sequencing, to help predict how the disease might spread.

It’s caused by a fungus found in desert soils and affects thousands of people each year.  

David Engelthaler is the study’s lead author. He says the Arizona species of the fungus is almost a million years old.  “The populations of this fungus in southern Arizona seem to be the oldest populations, and that’s likely where Coccidioides – that’s the name of the fungusfirst really emerged and started to radiate,” he says. 

Valley Fever spores likely migrated from Arizona to California after the Central Valley drained its ancient inland sea. There the fungus diverged into a separate species.

Valley Fever is now found in Mexico, parts of Central and South America and most recently Washington State. Engelthaler thinks animals carry it to new locations.  

The study appeared in mBio earlier this month.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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