Coccidioidomycosis symptoms, resulting from a fungus infection also known as "San Joaquin valley fever," are on the rise in California, Arizona, Nevada, New Mexico, and Utah, according to a new report from the Centers for Disease Control and Prevention (CDC).

Coccidioidomycosis is caused by inhaling Coccidioides immitis spores, which are typically found in arid soil. The fungal infection, endemic to dry regions of Mexico, Central and South America, and the southwestern United States, causes a flu-like illness that can lead to severe chronic pulmonary disease.

Today's Morbidity and Mortality Weekly Report (MMWR) from the CDC announced a major increase in coccidioidomycosis incidence over the past decade, from 5.3 per 100,000 people in the American Southwest (California, Arizona, Nevada, New Mexico, and Utah) in 1998 to 42.6 per 100,000 in 2011.

From 1998 to 2011, there were 111,717 cases of coccidioidomycosis from 28 states- 66 percent were from Arizona, 31 percent from California, and 1% from other endemic states. The fungal infection was most common among people aged 40 to 59 in California, and highest among people over age 60 in Arizona.

The CDC warns that "health-care providers should be alert for coccidioidomycosis among patients of all ages who live in or have traveled to endemic areas" if they display any flu-like respiratory symptoms, especially if they are elderly or have weak immune systems.

Coccidioidomycosis symptoms can include chest pain, chills, coughing, sore throat, and bloody phlegm. San Joaquin valley fever usually goes away without treatment, but in severe cases can present like chronic pneumonia. In people with weakened immune systems, it can be fatal when the Coccidioides fungus spread beyond the lungs.

The fungal infection can be difficult to diagnose, since its early symptoms are so similar to more common infections, and the CDC reports that many patients are initially given unnecessary antibiotics because doctors misdiagnosed them. According to Cedars-Sinai, reliable diagnosis methods include cultures grown from infected body fluids that show evidence of the Coccidioides fungus, or blood tests that reveal antibodies to it.

Antifungal drugs are typically recommended for coccidioidomycosis treatment in high-risk patients.

It's unclear what led to the increase in coccidioidomycosis symptoms over the past decade, though the CDC suspects that environmental disruptions in drought, rainfall, and temperature released larger amounts of Coccidioides spores from the soil than usual, or that human construction on previously undisturbed soil had the same effect.

There are no proven preventive measures for the coccidioidomycosis infection, but the CDC recommends that at-risk people in the American Southwest avoid San Joaquin valley fever by reducing exposure to dusty air that can contain spores of the Coccidioides fungus.