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Valley Fever (Coccidioidomycosis)

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Valley fever (coccidioidomycosis) facts

  • Valley fever (coccidioidomycosis) is a disease caused by a fungus, Coccidioides, which lives in the soil of relatively arid regions (southwest U.S.); its incidence is increasing.
  • People are infected by inhaling dust contaminated with Coccidioides; the fungus is not transmitted from person to person.
  • Although most people infected with Coccidioides have no symptoms, if symptoms develop, they usually occur in the lung and initially resemble the flu or pneumonia (cough, fever, malaise, sputum production, and shortness of breath).
  • Some people are more susceptible to infection (immunosuppressed people, those with HIV or cancer, and pregnant females) and may develop widespread disease.
  • Diagnosis is usually easy to accomplish, and the disease can be treated by several antifungal medications.
  • There is no vaccine available for valley fever (coccidioidomycosis).

What is valley fever (coccidioidomycosis)?

Valley fever (coccidioidomycosis) is a disease caused by fungi (Coccidioides immitis and C. posadasii species) that in about 50%-75% of normal (not immunocompromised) people causes either no symptoms or mild symptoms and those infected never seek medical care. When symptoms are more pronounced, they usually present as lung problems (cough, shortness of breath, sputum production, fever, and chest pains). The disease can progress to chronic or progressive lung disease and may even become disseminated to the skin, lining tissue of the brain (meninges), skeleton, and other body areas. The disease can also infect many animal types (for example, dogs, cattle, otters, and monkeys). From 1998 to 2011, the U.S. incidence has increased about tenfold to about 22,000 diagnosed individuals per year, according to the Centers for Disease Control and Prevention (CDC) although some researchers estimate as many as 15,000 per year.

Most microbiologists and infectious disease physicians prefer the name coccidioidomycosis because the word describes the disease as a specific fungal disease, and this term may replace valley fever in the future. This disease has several commonly used names (valley fever, San Joaquin Valley fever, California valley fever, acute valley fever, and desert fever). Other names get confused with valley fever (for example, rift or African valley fever, which is caused by a virus).

Coccidioidomycosis was first noted in the 1890s in Argentina when tissue biopsies of people with the disease showed pathogens that resembled coccidia (protozoa). During 1896-1900, investigators learned the disease was caused by a fungus, not protozoa, so the term "mycosis" was eventually added to "coccidia." The disease is often noted to occur in outbreaks, usually when soil is disturbed and dust arises, and when groups of people visit an endemic region (such as San Joaquin Valley or Bakersfield [in Kern County], Calif., and Tucson, Ariz., or parts of southern New Mexico or west Texas) during late summer and early fall. The disease is not transmitted from person to person; it is acquired from the environment via contaminated soil and dust. About 150,000 individuals are estimated to become infected each year in the U.S.

Medically Reviewed by a Doctor on 3/18/2016


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