Quick Answer: What is valley fever in Arizona and California?
What is valley fever? A fungal infection caused by breathing in Coccidioides spores found in soil, most common in Arizona and California.
Symptoms: Fatigue, cough, fever, headache, shortness of breath, night sweats, and sometimes rash.
Risks: Higher exposure in dusty outdoor environments; some people are more likely to develop severe illness.
When to see a doctor: If flu-like or respiratory symptoms persist or worsen, especially after living in or traveling to an endemic area.
Valley fever is a health concern in Arizona and California, where the fungus that causes the infection lives in dry soil. Its symptoms can look like the flu, pneumonia, or other common respiratory illnesses. Knowing the signs of valley fever and your potential exposure can help you recognize when to consult with a healthcare provider.
HealthyU Clinics serves patients across Arizona and California, giving our providers experience caring for people in communities where valley fever is a relevant health concern. Below, we explain what causes valley fever, the symptoms to watch for, who may face greater risks, and what Arizona and California residents should know about potential exposure.
What Is Valley Fever — and Why Is It So Common in Arizona?
Valley fever, or coccidioidomycosis, is a fungal lung infection caused by breathing in Coccidioides spores found in soil. The fungus is common in hot, dry areas, including much of southern and central Arizona and California’s San Joaquin Valley. According to the CDC, 20,000 cases are reported in the U.S. each year.
What Causes Valley Fever Exposure in Arizona
Valley fever comes from environmental exposure, not food, water, or ordinary contact with an infected person. Spores become airborne when construction, farming, wind, or other activities disturb soil and release Coccidioides spores into the air. This means exposure is not limited to rural areas; soil disturbance and construction can also create risks in urban areas such as Phoenix and Tucson.
How Valley Fever Spreads — and Doesn’t Spread
Valley fever is not contagious and does not normally spread from person to person or from pets to people through contact. People typically become infected by breathing airborne spores from the environment, although rare forms of transmission, such as through organ transplantation, have been reported.
Valley Fever Symptoms — and Why It Gets Misdiagnosed
Symptoms generally appear within 1-3 weeks of exposure, according to the CDC, and about 60% of exposed people do not develop symptoms at all. Because symptoms may resemble the flu, pneumonia, or other respiratory illnesses, misdiagnosis is not uncommon.
Common valley fever symptoms include:
- Fatigue
- Cough
- Fever
- Shortness of breath
- Headache
- Night sweats
Valley Fever vs. Seasonal Allergies — How to Tell the Difference
Much like distinguishing food poisoning from a stomach bug, valley fever and seasonal allergies may share similarities, but key differences remain.
Seasonal allergies commonly cause sneezing, itchy or watery eyes, and a runny nose. Patients should mention these concerns at an annual wellness exam or physical. Valley fever, on the other hand, is more likely to cause fever, persistent fatigue, cough, and sometimes a red rash. Symptoms alone cannot confirm valley fever, so a provider should evaluate persistent or worsening illness to determine whether testing is appropriate.
When Valley Fever Becomes Serious — Disseminated Infection
In about 1% of cases, the infection can spread beyond the lungs to areas such as the skin, bones, joints, or central nervous system. This condition is known as disseminated coccidioidomycosis. People with weakened immune systems and certain other risk factors have a greater risk of severe or disseminated disease. Medical evaluation is especially important when symptoms are persistent or severe.
California Valley Fever vs. Arizona Valley Fever — What’s Different
Valley fever occurs in Arizona and California, with Arizona’s desert regions and California’s San Joaquin Valley among the best-known endemic areas in the U.S. The infection is the same in both states, but exposure patterns and case reporting vary by region.
| Valley Fever in Arizona | Valley Fever in California | |
|---|---|---|
| Primary Risk Areas | Most cases occur in desert regions, particularly central and southern Arizona. | Risk is highest in the Central Valley and Central Coast, with cases also reported elsewhere in the state. |
| Key Counties & Metro Areas | Maricopa and Pima counties include the Phoenix and Tucson metro areas. | Kern, Kings, Tulare, Fresno, and San Luis Obispo counties have historically high rates. |
| Reported Cases | Arizona reports more cases than any other state. | California reports the second-highest number of cases nationally. |
Arizona’s Endemic Zones — Where Risk Is Highest
Valley fever is especially common in central and southern Arizona, including Maricopa County, home to Phoenix, and Pima County, home to Tucson. Because Coccidioides can become airborne when dry soil is disturbed, residents may encounter exposure during dusty conditions, construction, or other soil-disturbing activities.
California’s Endemic Zones — and the Expanding Range
Valley fever in California is most common in the Central Valley and Central Coast, including Kern, Kings, Tulare, Fresno, and San Luis Obispo counties. Research suggests that suitable Coccidioides habitat could expand farther north as climate conditions change, making awareness relevant beyond California’s historically highest-risk areas.
Who Is Most at Risk for Valley Fever in Arizona and California
Valley fever awareness and healthcare resources are particularly relevant for patients in Arizona and California. Anyone who lives in or visits an area where Coccidioides grows can be exposed, but some people face greater exposure or a higher risk of severe illness.
In Arizona and California, risk factors generally fall into two groups:
Higher exposure risk:
- Construction, excavation, and agricultural workers
- Military personnel and field researchers working in dusty areas
- Hikers, campers, and off-road recreation users
- People who frequently encounter disturbed desert soil
Higher risk of severe illness:
- People with weakened immune systems
- Pregnant women
- Adults 60 and older
- People with diabetes
- People of Black or Filipino descent
Why New Arizona Residents Face Elevated Risk
People moving to Arizona from areas where valley fever is uncommon may be unfamiliar with the infection and its symptoms. New residents, especially those in the Phoenix and Tucson areas, should be aware of possible exposure to Coccidioides and mention recent dust or soil exposure to a healthcare provider if respiratory symptoms persist.People moving to Arizona from areas where valley fever is uncommon may be unfamiliar with the infection and its symptoms. New residents, especially those in the Phoenix and Tucson areas, should be aware of possible exposure to Coccidioides and mention recent dust or soil exposure to a healthcare provider if respiratory symptoms persist.
Dogs and Valley Fever — What Pet Owners Should Know
Dogs can also develop valley fever after breathing Coccidioides spores from the environment, particularly in endemic areas of Arizona. Dogs do not transmit valley fever to people. However, a diagnosis can remind you that both pets and people living in the same region may encounter the fungus in their environment.
Dogs can also develop valley fever after breathing Coccidioides spores from the environment, particularly in endemic areas of Arizona. Dogs do not transmit valley fever to people. However, a diagnosis can remind you that both pets and people living in the same region may encounter the fungus in their environment.
Frequently Asked Questions
Is valley fever contagious?
No. Valley fever is typically contracted by breathing Coccidioides spores from the environment, not through contact with people or pets.
How is valley fever diagnosed?
Providers typically use blood tests, sometimes along with chest imaging or respiratory samples, to diagnose valley fever.
Does valley fever go away on its own?
Mild cases can resolve without antifungal treatment, but severe cases or people at higher risk may require medication and medical monitoring.
What time of year is valley fever most common in Arizona?
Exposure can occur year-round, with Arizona historically seeing seasonal increases tied to hot, dry conditions and periods after summer rains.
Can you get valley fever in California?
Yes. Valley fever is well established in California, especially in the Central Valley and Central Coast, though cases occur elsewhere in the state.
Disclaimer: Any advice or information shared on our blog, website, or other online communication forum is intended for informational purposes only and is not to be considered a substitute for any professional medical advice or other advice. HealthyU Clinics does not make any representations or warranties and expressly disclaims all liability regarding any treatment, action, or effect on any person based on the general information provided through our blog, website, or other online communication forum. For specific concerns or if you need medical advice, please contact HealthyU Clinics to schedule an appointment with a qualified medical professional.
