Valley fever

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at July 29, 2016
StartDiseasesValley fever

Valley fever is a respiratory infection caused by inhaling spores of the Coccidioides (kok-sid-e-OY-deze) fungus. Other common names for this type of fungal infection are coccidioidomycosis, desert fever, or desert rheumatism. It is not contagious and is not spread from one person to another or through contact with animals. Symptoms are generally mild and usually result in a full recovery without the need for medical treatment.


Definition & Facts

According to the Centers for Disease Control and Prevention (CDC), 40 percent of people who contract valley fever show no symptoms and never seek medical treatment. The other 60 percent experience mild flu-like symptoms.

Those who have recently moved to an area where the disease naturally occurs are at a higher risk, and infection is most likely to impact adults over the age of 60. Most of those infected gain immunity after the initial exposure and recurrence is unlikely.

Complications arise when the initial infection fails to resolve and continues to progress to a more serious condition. This is most likely to occur among patients with weakened immune systems including those who have had an organ transplant or who have been diagnosed with HIV.

Certain medications such as prednisone or methotrexate can also cause immunosuppression and increased risk. Although studies have been unable to pinpoint the reason, patients of black or Filipino ethnicity have shown a greater likelihood of developing this infection. Women who are pregnant should seek medical attention if infection is suspected.

Symptoms & Complaints

Initial symptoms typically appear one to three weeks after inhalation of the spores. The most common complaints include mild to severe chest pain, coughing, fever, chills, night sweats, headache, fatigue, and joint aches.

Patients may also experience a painful rash on the chest, arms, and back. The rash will appear red and bumpy and may possibly blister. As infection progresses, the rash may turn brown or begin to erupt into pimple-like bumps.

If full recovery does not occur, Valley fever may progress to a chronic form of pneumonia. These symptoms include low grade fever, unexplained weight loss, chest pain, cough that produces bloody discharge, and nodules in the lungs.

The most severe form of the condition is referred to as disseminated coccidioidomycosis. This occurs when the infection spreads (disseminates) into other parts of the body such as the skin, bones, liver, brain, and heart.

Symptoms vary depending on the location of the new infection and can include skin ulcers and lesions, painful lesions on the skull, spine, or other bones, and painful swelling in the knees, ankles, and other joints. In rare cases Valley fever can result in meningitis, a life-threatening infection of the membranes and fluid surrounding the spinal cord and brain.


There are two types of fungi that cause Valley fever, the Coccidioides immitis or Coccidioides posadasii. Both thrive in areas that experience mild winters and arid summers, particularly the southwest United States, northern Mexico, and parts of Central and South America. A CDC report states that of the reported cases in the United States, over 65 percent occur in Arizona, 30 percent in California, and the remaining cases are predominately in Nevada, Utah, and Mexico. 

Infection usually occurs when there is a disruption to the soil and the fungi’s spores are stirred up into the air. Farmers, construction workers, archeologists, and paleontologists working in these geographical areas are at higher risk. Riding all-terrain vehicles (ATVs) or bicycles in the desert may increase risk of infection, and there is often a spike in infections when there is an earthquake or other weather event that kicks up a lot of dust.

The spores are microscopic and can be carried hundreds of miles by the wind, so it is possible to contract the infection without engaging in any activities that are considered risk factors. The number of reported cases have increased over the years, most likely due to increased travel to locations where the fungus is prevalent, changes in temperature and rainfall that affect spore production and circulation, and increased awareness amongst the medical community.

Diagnosis & Tests

When patients seek medical attention, symptoms are often vague and overlap with symptoms that occur in other illnesses. This makes the infection difficult to diagnose without testing. A chest X-ray does not distinguish the infection from those caused by other lung diseases, and nodules caused by Valley fever are often mistaken for cancer. To reach a positive diagnosis, sputum may be tested for the presence of coccidioides organisms, or blood may be drawn to test for antibodies against the fungus that causes Valley fever. 

Treatment & Therapy

When symptoms occur in otherwise healthy adults, the most common treatment is bed rest and fluids. Patients who live in or have visited areas where Valley fever are common and think they could have been exposed should mention this to their physicians. If infection is suspected, close monitoring is recommended. The severity of symptoms and length of time needed to fully recover depends on the general overall health of the patient and the number of spores that have been inhaled.

Symptoms may last a few weeks to several months while fatigue and joint aches may persist well beyond that. For severe cases that are not resolving on their own, doctors may prescribe antifungal medications such as fluctonazole or itraconazole. Two new medications, voriconazole and posaconazole, have also been effective in treating the condition. In extreme cases, the infection may be treated with intravenous antifungal medication such as amphotericin B.

Prevention & Prophylaxis

Although researchers are actively working on developing a vaccine, none are available at this time. In areas where valley fever is common, the best prevention lies in taking simple precautions.

Tightly closing windows and doors, staying indoors during dust storms, and wetting the soil prior to digging can all help to avoid the inhalation of infectious spores. Those at increased risk of infection might also consider wearing a dust mask during the summer months when the chance of infection is at its highest.

As the medical community becomes more aware of the possibility of valley fever infection, the chance of misdiagnosis decreases. Individuals who have a reason to suspect infection can also help to ensure proper treatment by informing physicians of their risk factors.