What Is Valley Fever?
Valley Fever, known medically as Coccidioidomycosis (kok-SID-ee-oy-doh-my-KOH-sis), is a lung infection caused by the fungus Coccidioides. It's not contagious between people — instead, it spreads through inhaling fungal spores found in the soil of certain dry, arid regions. Despite being relatively common in affected areas, Valley Fever is frequently misdiagnosed because its symptoms closely resemble those of the flu, pneumonia, or even COVID-19.
Where Does the Fungus Live?
The Coccidioides fungus thrives in the dry, alkaline soils of:
- The San Joaquin Valley and other parts of California
- Arizona, especially the Phoenix and Tucson areas
- Parts of Nevada, Utah, New Mexico, and Texas
- Regions of Mexico and Central and South America
The spores become airborne when soil is disturbed by wind, construction, farming, or outdoor activities. Climate change is expanding the fungus's geographic range, making awareness increasingly important beyond traditional hotspot regions.
How Does Infection Occur?
Infection happens when a person inhales airborne Coccidioides spores. Once inside the lungs, the spores transform into a different form of the fungus and can cause an inflammatory response. In most healthy people, the immune system contains the infection without it spreading. However, in some individuals — particularly those with weakened immune systems — the infection can disseminate (spread) to other organs including the bones, joints, skin, and even the brain.
Recognizing the Symptoms
About 60% of people infected with Coccidioides develop no symptoms at all. For those who do, symptoms typically appear 1 to 3 weeks after exposure and may include:
- Fatigue (often the most pronounced symptom)
- Cough — dry or productive
- Fever and chills
- Chest pain or tightness
- Shortness of breath
- Headaches
- Night sweats
- Joint aches and muscle pain
- A characteristic rash — often a red, bumpy rash on the lower legs (erythema nodosum)
Most people recover fully within a few weeks to months. However, some experience chronic pulmonary Valley Fever, where the lung infection persists or returns, and a small percentage develop disseminated Valley Fever, which is far more serious.
Who Is at Greatest Risk?
While anyone can get Valley Fever, certain groups face a higher risk of developing severe or disseminated disease:
| Risk Group | Why They're at Higher Risk |
|---|---|
| People with HIV/AIDS or organ transplant recipients | Compromised immune systems struggle to contain the fungus |
| Pregnant women (especially third trimester) | Immune changes during pregnancy increase vulnerability |
| People with diabetes | Altered immune responses raise infection severity |
| African American and Filipino individuals | Genetic factors appear to increase dissemination risk |
| Outdoor workers (construction, military, farming) | Greater exposure to dust and disturbed soil |
Diagnosis: Why It's Often Missed
Valley Fever is routinely misdiagnosed as bacterial pneumonia, the flu, or other respiratory illnesses. Diagnosis typically requires blood tests that detect antibodies to Coccidioides, and sometimes chest X-rays or CT scans to evaluate lung involvement. If you live in or have visited an endemic region and have persistent respiratory symptoms, ask your doctor specifically about testing for Valley Fever.
A Note on Treatment
Many mild cases resolve without antifungal treatment, though rest and symptom management are important. More severe or disseminated cases require antifungal medications, which a physician must prescribe and monitor. Early diagnosis is key to preventing complications — don't dismiss lingering fatigue and respiratory symptoms if you live in or have traveled to an endemic area.