What is valley fever?

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Valley fever, also known as San Joaquin Valley fever or coccidioidomycosis, is an infection by the fungus Coccidioides immitus. As the name "valley fever" implies, the fungus is found only in certain regions. In the United States, it is found in the desert Southwest, including California's San Joaquin valley. It also grows in parts of Central and South America. The fungus lives in the soil and releases its spores into the air. Outbreaks occur during weather changes, dust storms and earthquakes, all of which increase the amount of spores dispersed into the air.

People become infected by inhaling the spores. About 60 percent of people infected in this way have no symptoms at all. The other 40 percent may have chest pain, weakness, fever, chills, night sweats, joint aches and a cough that may produce phlegm. Some people also have a skin rash and enlarged lymph nodes. In the vast majority, the illness goes away by itself within a few weeks without any further problem.

In about 5 percent of infected people who get better without complications, future chest X-rays will show small spots (nodules) or even holes (cavities) in the lung tissue. These changes do not indicate a threat to the health of the patient, but they could be mistaken for lung cancer or another problem later in life.

In a few patients, the illness does not go away but progresses to a severe (and in rare cases fatal) pneumonia. In another rare complication, which occurs in fewer than 1 percent of those infected, the infection can spread outside the lung. This so-called disseminated disease is for some reason more common in men, pregnant women, and individuals of dark-skinned races, such as those of African, Filipino and Native American descent. It is most common, however, in people with immune-system disorders such as HIV infection.

The most common form of the disease usually requires no treatment. Medications are needed for people with severe illness and those at high risk for disseminated disease. The usual treatments are amphotericin B, a somewhat toxic antifungal agent given through an IV, or fluconazole, a less-toxic drug that can be taken as an IV or pills.