An infection with the fungus coccidioides.
The coccidioides fungus is found in soil and causes infection when inhaled. People with suppressed immune systems are particularly at risk.
The initial form is often mild, with few symptoms. When symptoms do occur, they may resemble those of the flu, including fever, cough, chills and chest pain.
Mild cases clear up on their own. If symptoms don't improve, antifungal medication may be necessary.