Coccidioidomycosis (Valley Fever)

How people get infected

Coccidioides immitis and Coccidioides posadasii grow in the top layers of desert soil. When soil is disturbed by construction, farming, digging, wind storms or earthquakes, spores become airborne and are inhaled. Infection is most common in summer and fall, especially after wet winters followed by dry, windy conditions.

Most cases in the US occur in Arizona and California, with tens of thousands of reported cases each year, and many more go undiagnosed. Visitors can become ill after returning home, which can delay diagnosis. See valley fever for a plain-language overview.

Forms and symptoms

Asymptomatic infection

About 60 percent of people have no symptoms. They develop lifelong immunity in most cases.

Primary pulmonary coccidioidomycosis

Symptoms begin 1 to 3 weeks after exposure:

• fatigue, often marked and long-lasting
• cough, chest pain and shortness of breath
• fever, chills and night sweats
• headache
• muscle and joint aches ("desert rheumatism")
• a rash: red, tender lumps on the shins (erythema nodosum) or a red rash on the trunk or limbs

It is often mistaken for community-acquired pneumonia. In endemic areas, valley fever causes a significant share of pneumonias. Most people recover over weeks to months, though fatigue can persist.

Chronic pulmonary disease

A small proportion develop lung nodules, cavities or chronic pneumonia lasting months, sometimes with coughing up blood.

Disseminated coccidioidomycosis

In about 1 percent of symptomatic cases, the infection spreads through the bloodstream to:

• skin: sores, nodules or abscesses
• bones and joints: especially the spine
• meninges: coccidioidal meningitis, the most serious form, needing lifelong treatment

Who is at risk of severe disease

• people with weakened immune systems: HIV, organ transplant, cancer chemotherapy, TNF inhibitors and other immunosuppressants, long-term steroids
• pregnant people, especially in the third trimester
• people with diabetes
• people of African American or Filipino ancestry, who have a higher risk of dissemination
• older adults
• outdoor workers in endemic areas: construction, agriculture, archaeology, military, wildland firefighters

Diagnosis

Testing is recommended for anyone with pneumonia-like symptoms who lives in or traveled to an endemic area.

• Blood antibody tests: enzyme immunoassay (EIA), immunodiffusion and complement fixation. Complement fixation titers help gauge severity and response to treatment. Antibodies may take weeks to appear, so tests may be repeated.
• Fungal culture or PCR from sputum, tissue or fluid.
• Chest X-ray or CT: pneumonia, nodules, cavities or enlarged lymph nodes.
• Lumbar puncture if meningitis is suspected.
• Bone scans or MRI for suspected bone involvement.

Treatment

Watchful waiting

Many healthy people with mild illness recover without antifungal medicine. They are monitored with follow-up visits, blood tests and chest X-rays for 1 to 2 years to ensure the infection resolves.

Antifungal medicines

Treatment is recommended for moderate to severe illness, prolonged symptoms, and people at high risk:

• fluconazole or itraconazole taken by mouth for 3 to 6 months or longer
• amphotericin B for severe, rapidly progressive or disseminated disease, and during pregnancy (azoles can harm the fetus in the first trimester)
• lifelong fluconazole for coccidioidal meningitis
• newer azoles (voriconazole, posaconazole, isavuconazole) for difficult cases

Surgery

Sometimes needed to remove cavities that bleed or rupture, or to drain abscesses and treat bone infection.

Prevention

There is no vaccine. In endemic areas:

• avoid dusty outdoor activities on windy days, especially if at high risk
• wet soil before digging, and use an N95 respirator for dusty work
• keep windows closed during dust storms
• employers should provide dust control and respiratory protection for outdoor workers

Frequently asked questions

What are the symptoms of valley fever?

Common symptoms are fatigue, cough, fever, chest pain, shortness of breath, headache, night sweats, joint aches and sometimes a rash with tender red lumps on the shins. Symptoms appear 1 to 3 weeks after exposure and can last weeks to months.

Is coccidioidomycosis contagious?

No. Coccidioidomycosis is not spread from person to person or from animals to people. It is caught only by breathing in fungal spores from the environment, mostly in dusty desert areas of the southwestern US and Mexico.

How is valley fever diagnosed?

Usually with blood tests that detect antibodies to Coccidioides. Sometimes doctors culture the fungus from sputum or tissue, or use PCR. Chest X-rays or CT scans show lung involvement. Tests may need repeating because antibodies take time to appear.

Does valley fever go away on its own?

In many healthy people, mild valley fever resolves without treatment over weeks to months, though fatigue can last longer. People with severe illness, weakened immunity, pregnancy or certain risk factors need antifungal medicine. Follow-up is recommended to make sure it clears.

Can you get valley fever more than once?

Usually not. Recovery typically gives lifelong immunity. However, the infection can reactivate later if the immune system becomes severely weakened, for example after an organ transplant or with advanced HIV.