FRESNO, Calif. -- 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.
"Research has shown that when soil is dry and it is windy, more spores are likely to become airborne in endemic areas," said Dr. Gil Chavez, deputy director of the Center for Infectious Diseases at the California Department of Public Health.
Long-standing concerns about valley fever were heightened last week when a federal health official ordered the transfer of more than 3,000 exceptionally vulnerable inmates from two San Joaquin Valley prisons where several dozen have died of the disease in recent years. A day later, state officials began investigating an outbreak in February that sickened 28 workers at two solar power plants under construction in San Luis Obispo County.
Although millions of residents in central California face the threat of valley fever, experts say people who work in dusty fields or construction sites are most at risk, as are certain ethnic groups and those with weak immune systems.
Valley fever is often difficult to detect. The illness usually causes mild to severe flu-like symptoms, but in about half the infections, the fungus -- called Coccidioides -- results in no symptoms.