California and federal public health officials say valley fever, a potentially lethal but often misdiagnosed disease infecting more and more people around the nation, has been on the rise as warming climates and drought have kicked up the dust that spreads it.

The fever has hit California’s agricultural heartland particularly hard in recent years, with incidence dramatically increasing in 2010 and 2011. The disease — which is prevalent in arid regions of the United States, Mexico, Central and South America — can be contracted by simply breathing in fungus-laced spores from dust disturbed by wind as well as human or animal activity.

The fungus is sensitive to environmental changes, experts say, and a hotter, drier climate has increased dust carrying the spores.