Valley fever --- a potentially deadly but often misdiagnosed condition --- is on the rise as warming temperatures and drought have kicked up dust that spreads the disease, say California and federal public health officials.
The fever has hit California's agricultural regions particularly hard over recent years, with the number of cases spiking in 2010 and again in 2011.
The disease, prevalent in arid regions of the United States, Mexico, Central and South America, can be contracted by breathing in dust containing fungus-infected spores.
Medical experts say the fungus is sensitive to environmental changes, and the hotter, drier climate as of late has exacerbated dusty conditions, thereby making the spread of the laced spores worse.
"Research has shown that when soil is dry and it is windy, more spores are likely to become airborne in endemic areas," Gil Chavez, deputy director of the Center for Infectious Diseases at the California Department of Public Health, told the Associated Press.
Ongoing concerns about valley fever were underscored last week when a federal health official ordered the more than 3,000 state inmates deemed particularly vulnerable to the fever transferred out of two San Joaquin Valley prisons where dozens of people have died of the disease in recent years.
A day after the transfer was ordered, state officials then began investigating a fever 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 are at risk of contracting threat of valley fever, those who work in dusty fields or construction sites are at most risk, along with certain ethnic groups and those with weak immune systems.
Newcomers to the state and those just passing through also may be more susceptible to the disease.
The number of valley fever cases nationally rose by more than 850 percent from 1998 through 2011, according to the Centers for Disease Control and Prevention.
There were more than 20,400 reports of the fever in 2011, mostly in California and Arizona.