California and federal public health officials say valley fever, a potentially lethal disease, has been on the rise as warming climates and drought have kicked up the dust that spreads it.
The disease can be contracted by simply breathing in fungus-laced spores from dust disturbed by wind as well as human or animal activity.
Data shows the number of valley fever cases rose by more than 850 percent nationwide over the past 13 years, with most cases reported in California and Arizona.
Experts say rainfall followed by hotter, drier weather makes more spores airborne, increasing the number of cases. Improved reporting methods and better diagnosis also partially explain the increase.
A federal health official last week ordered the transfer of more than 3,000 vulnerable inmates from two Central California prisons where several dozen have died of the disease.