Valley fever

Definition
Coccidioidomycosis, also known as San Joaquin valley fever or more simply valley fever, is a fungal infection.

Causes/associated factors
Valley fever is caused by the fungus Coccidioides immitis, which is found in the soil in certain dry, hot areas of the southwestern United States, Mexico, and Central and South America. In the United States, residents of California, Arizona, New Mexico and Texas or people who have traveled to or through these areas report most of the about 100,000 new cases of valley fever each year. The number of cases is increasing because of the massive migration of people to these endemic areas (confined to a particular area or people) that were previously sparsely populated.
Valley fever is most common in the summer, affecting both humans and animals. Valley fever can affect anyone, but people who have higher exposure to outdoor dust -- such as people who work in construction, agriculture or archaeology -- have the highest risk.

Valley fever has two forms: primary and disseminated (progressive).

Primary valley fever may have no symptoms or be an acute (abrupt or sudden) illness almost always involving the respiratory system.

Disseminated (progressive) valley fever is a chronic, potentially life-threatening complication involving nearly any part of the body. The risk for this type of valley fever, which develops in 1 to 2 percent of cases, is higher for pregnant women in the third trimester and those who have weak immune systems, such as people who received an organ transplant, are on long-term corticosteroid therapy, or have HIV, AIDS or lymphoma. For unclear reasons, African Americans and Filipinos are also at higher risk for disseminated infection. It can occur soon after the primary infection or develop weeks, months or even years later and is often difficult to cure.

Transmission
Valley fever spreads by inhaling fungal spores of Coccidioides immitis. The fungus may also be inhaled through accidental exposure to lab specimens. The fungus does not spread from person to person, animal to person or animal to animal.
For a primary infection, the incubation period (time from exposure until symptoms appear, if they appear at all) is one to four weeks. Clusters of illness may develop 10 to 30 days after a group of susceptible people are exposed to dust in an endemic area by unearthing ruins and relics, rock hunting, practicing military maneuvers, doing construction, or engaging in similar activities. Windstorms can carry the fungus to nonendemic areas, which may also cause case clusters of illness.

Recovery from valley fever typically produces lifelong immunity. If you have a weak immune system, however, you may experience a recurrent bout of the illness.


Signs/symptoms
About 60 percent of people with valley fever have no symptoms. If symptoms develop, they may be similar to the flu. For several weeks, you may notice:
fever and chills
dry cough
chest pain
headache
backache
painful joints
fatigue
appetite loss
occasionally, a rash
In some cases, valley fever may lie dormant (inactive) for years before causing symptoms.


Diagnosis
The doctor will ask questions about your medical and travel history and do a physical exam. Because valley fever can lie dormant for years, it's important to include even remote travel history to the southwestern United States. You may need further diagnostic tests, such as blood tests to detect antibodies (compounds that help neutralize or destroy foreign substances in the blood) to the fungus, a chest X-ray and analysis of sputum (fluid produced upon coughing), urine, pus and cerebrospinal fluid. Skin testing may be done in some cases.

Treatment
Typically, no treatment is needed for the primary form of valley fever if you have no symptoms or underlying health problems. The condition usually clears up on its own. Your doctor may recommend rest and other specific measures to control your symptoms, however. Your progress will be monitored over the course of several weeks or months.
Treatment is necessary if you have severe symptoms, develop lung complications, or the infection is disseminated. Treatment may also be recommended for a primary infection if you're at increased risk of developing a disseminated infection. (Again, this includes pregnant women in the third trimester, African Americans, Filipinos, people who have diabetes and those who have weak immune systems.)

When treatment is necessary, the type of treatment will depend upon how ill you are. If the infection has spread or you are severely ill, intravenous doses of the antifungal medication amphotericin B are often prescribed for several months. Alternate medications may include ketoconazole, fluconazole and itraconazole. These medications are taken orally, with the exception of fluconazole, which can be taken orally or intravenously. The choice of medication will depend on the type of infection you have and its severity. Expert consultants are often involved in the decision. People who have weak immune systems may need the drugs indefinitely to prevent recurrences.

Rarely, surgical drainage of lung fluid or abscesses (collections of pus) or other surgical treatments may be helpful.


Complications
Sometimes, a primary valley fever infection can cause permanent changes in the lungs, such as nodules or cavities. These changes usually cause no problems. In some cases, a biopsy (taking a tissue sample for further examination) is needed to verify that a nodule is not cancerous. Cavities can sometimes rupture or develop other problems, which may require further treatment or surgery.
Disseminated valley fever can lead to lung lesions, abscesses in bones and other organs, chronic skin ulcers that don't heal, swollen joints, persistent headaches or meningitis (inflammation of the membranes surrounding the brain and spinal cord). This type of valley fever can be fatal, especially if it's associated with meningitis or severe respiratory symptoms.


Pregnancy-specific information
Again, pregnant women who contract valley fever have a higher risk of developing a disseminated infection, especially if it occurs later in the pregnancy.

Senior-specific information
Growing older is not a risk factor for this condition.

Prevention
In endemic areas, dust can be controlled by planting grass and oiling unpaved airfields. It also helps to wear face masks, wet soil, and ride in air-conditioned vehicles with the windows rolled up. People from nonendemic areas should avoid dusty activities, such as construction. Blood tests can identify who is susceptible to the illness. If you're handling lab cultures, use extreme caution. Although there is currently no vaccine for valley fever, research continues.