Valley fever is on the rise. Cases of this dangerous and even fatal condition have tripled in the past decade, to the point where the Centers for Disease Control and Prevention (CDC) have dubbed it a "silent epidemic." Fewer than 1,500 cases were reported in California in 2001; by 2010 that number had risen to more than 16,000. Although valley fever can be found throughout the American Southwest, most cases have turned up in California and Arizona.

So what is valley fever? It's not a virus or bacterial condition. Technically it is called Coccidioidomycosis, a condition caused by exposure to the airborne fungus Coccidioides, which is common in dry, dusty areas. Although many people who encounter this fungus don't go on to experience symptoms, it can cause a wide range of problems in others, especially people who have lowered immune systems. People of African-American or Filipino descent and pregnant women in their third trimester have also shown greater susceptibility to valley fever, which most commonly manifests as flu-like symptoms such as fever, cough, headache, rashes, muscle aches or joint pain. In more advanced cases, valley fever can cause skin lesions, chronic pneumonia, meningitis and bone or joint infections, any of which can be fatal.

map of valley fever rangeLuckily, valley fever is only transmitted via direct contact with the fungal spores. It can't be transmitted from person to person, so people who experience symptoms don't need to worry about spreading it to friends and family. Unfortunately, it doesn't take much exposure to the fungus to experience problems. As the CDC says, "it only takes one breath" of the fungus to become infected.

For most people, valley fever will fade and people should recover with little complication. Others may need to be treated with antifungals, although they are not 100 percent effective and people can still experience relapses after treatment. In either case, early diagnosis is critical, especially since valley fever manifests so similarly to the flu or other respiratory diseases. Treatment by health care providers who can recognize the symptoms and the nearby threats is often the quickest path to reducing symptoms. The Mayo Clinic recommends that people who think they may have valley fever document their symptoms and think about where they could have become exposed. Valley fever can usually be diagnosed via blood tests, which would show signs of antibodies fighting the fungus, or a culture from coughing, which should show the presence of the fungus itself.

So why is the disease on the rise? The CDC says some scientists are looking into changing weather patterns and hotter temperatures, which may have helped the fungus to spread outside of its normal habitat. Changing rain patterns could also have had an effect, as heavy rainfalls followed by long, dry periods could allow more of the fungus to enter the air with dust and wind. It's also possible the increase in cases is a simple side effect of the increased human population in the region.

No vaccine exists for Coccidioidomycosis, but the CDC recommends that people working in or near dusty environments, such as construction sites, wear an N95 mask to reduce the chance of ingesting the fungus. Indoor HEPA filters can also improve air quality and reduce the chance of infection. Finally, they suggest keeping sores and cuts covered and clean, as the fungus has been known to enter through wounds in addition to the lungs.

By the way, humans aren't the only ones at risk of valley fever. Cats and dogs can also contract Coccidioidomycosis, so keep an eye on your critters when conditions could be most risky.

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Valley Fever range map courtesy CDC