Anticipating a Rise in Coccidioidomycosis ("Valley Fever") Cases in Los Angeles County

Zachary Rubin, MD

September 8, 2023

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Key Points

  • Clinicians working in LA County should be prepared for an increase in cases of coccidioidomycosis. High rainfall this past winter may lead to an increase in cases in late summer and fall.
  • Consider coccidioidomycosis in patients who live, work, or travel to an endemic area and have a compatible clinical syndrome, such as community-acquired pneumonia (CAP). Endemic areas in LA County include Antelope Valley and the west and north parts of the San Fernando Valley. Coccidiomycosis should also be considered in patients with CAP of unknown etiology who are not responding to empiric antibiotics.
  • Early testing, diagnosis, and initiation of treatment of in high-risk patients can help prevent the most serious complications of coccidioidomycosis.
  • For more information or questions, call the DPH Acute Communicable Disease Control Program at 213-240-7941.




Coccidioidomycosis is a disease caused by inhaling spores from the fungus Coccidioides which lives in dry soil and dust. While most infections are asymptomatic, clinical illness ranges from acute pneumonia (Valley fever) to severe disseminated disease.

Coccidioidomycosis cases are increasing in California and LA County (see LA County graph). The highest incidence of cases in California are diagnosed among patients living in the hot and arid southern areas of the San Joaquin Valley, though there has been an increase in incidence in other areas of California. See CDPH Coccidioidomycosis dashboard. A recent study in California found that the wet winters followed by hot, dry summers increased the transmission of coccidioidomycosis.

A summary of coccidioidomycosis is presented below. For more detailed clinical guidance, please see the reference documents at the end of this article.

Chart showing Coccidiodomycosis Case Count and Incidence Rate by Year in Los Angeles County

* Excludes Pasadena and Long Beach
Source: Los Angeles County Department of Public Health, Acute Communicable Disease Control Program



  • Coccidioidomycosis is caused by inhaling spores from airborne dust or soil.
  • The risk is higher when the soil is disrupted such as during strong winds, construction, excavation, farming, earthquakes, and archaeological digs.
  • It is not transmitted person-to-person.

Endemic areas

  • Coccidioides is known to be endemic to the southwestern United States, south-central Washington, parts of Mexico, and South and Central America.
  • In California, most cases are reported from the Central Valley and Central Coast regions. Cases have been increasing outside these regions as California experiences more drought.
  • In Los Angeles County, people who live and work in Antelope Valley and the north and west parts of the San Fernando Valley are at greatest risk of infection.

Estimated areas with coccidiomycosis in the US

Map of estimated areas with coccidiomycosis in the US



Clinical Presentation

  • About 60% of infected people do not develop any symptoms.
  • Symptoms, if present, may appear 1-3 weeks after exposure. See box.


Symptoms and Signs of Primary Coccidioidomycosis

  • Fever
  • Fatigue
  • Night sweats
  • Cough
  • Chest pain
  • Dyspnea
  • Hemoptysis
  • Headache
  • Myalgia/arthralgia
  • Erythema nodosum
  • Erythema multiform


  • The most common presentation of primary pulmonary coccidioidomycosis is cough and persistent fatigue, with only about half of patients reporting fever. Symptoms can be indistinguishable from community-acquired pneumonia (CAP).
  • Systemic complaints — which include fatigue, myalgia, arthralgia, and night sweats — may last for weeks to months. Erythema nodosum and erythema multiforme also may occur.
  • Infections of bone and the central nervous system are possible and can be life threatening.

Complications and risk factors

  • Complications are rare but can be severe. Approximately 5-10% of infections result in significant pulmonary disease (e.g., bronchiectasis, cavitary pneumonia, pulmonary fibrosis). About 1% of illnesses result in extra-pulmonary disseminated disease that can involve multiple organ systems, last life-long, and lead to outcomes such as meningitis and death.
  • Risk factors for severe pulmonary complications include:
    • Advanced age (>65)
    • Diabetes
    • Smoking
    • Exposure to a high inoculum
    • Certain ethnicities (people of African American, Filipino, and Pacific Island descent).
  • Risk factors for disseminated disease include people who are pregnant or have depressed cellular immune function (e.g., HIV/AIDS, TNF inhibitors, chemotherapy).



  • Consider coccidioidomycosis in patients who live, work, or travel to an endemic area and have a compatible clinical syndrome, such as CAP. Coccidiomycosis should also be considered in patients with CAP of unknown etiology who are not responding to empiric antibiotics. Prolonged illness or CAP unresponsive to antimicrobial therapy increases the likelihood of coccidioidomycosis.
  • An accurate diagnosis can reduce unnecessary exposure to antibiotics, facilitate appropriate counseling, and enable potential therapy.
  • Chest radiograph findings may include focal or diffuse pulmonary infiltrates, hilar adenopathy, and pleural effusion.
  • Imaging and potential lumbar puncture is recommended for patients with persistent headaches or neurological symptoms.
  • Skeletal imaging is recommended for patients with spinal or other bone or joint pain to identify potential osseous spread of disease.

Laboratory diagnosis

  • Serologic tests to detect IgM and IgG antibodies are used most often to diagnose coccidioidomycosis. See CDC clinical testing algorithm for patients with CAP.

Algorithm for Coccidioidomycosis Diagnosis

  • The interpretation of serologic tests for coccidioidomycosis can be challenging. There are a few things to keep in mind:
    • Serologic tests can be falsely negative early in the course of disease, and sometimes in patients with limited pulmonary disease. In these scenarios, repeat serology and/or adjunctive tests (tissue for culture and microscopy and blood or urine antigen testing) may be helpful.
    • Enzyme-linked immunoassays (EIA) IgG and IgM are the most common diagnostic tests for Coccidioides, but the IgM can be prone to false positive results. Clinicians may consider follow-up testing with immunodiffusion (ID) or complement fixation (CF) to rule out false positives and confirm the diagnosis.
    • Consulting with an experienced physician can be helpful in atypical cases.
  • Culture and microscopy are both helpful in evaluating coccidioidomycosis infections in tissues as Coccidioides is never part of patients’ normal microbiota.
  • Antigen testing of urine or blood can be useful in diagnosing illness and may be a helpful adjunct to antibody testing.
  • PCR testing for coccidioidomycosis has not been a commonly used test in clinical settings in the past but may become a more common testing modality in the future.
  • Coccidioides skin testing is available but is not recommended for evaluating active clinical infections.
  • When evaluating patients for potential disseminated disease, it is best to involve physicians who are experienced in diagnosing and treating these infections.



  • Most healthy patients with mild symptoms do not need antifungal therapy. Supportive care should be provided as needed. Symptoms of prolonged fatigue can be managed by physical therapy for re-conditioning.
  • Infectious Diseases Society of America (IDSA) guidelines suggest antifungal treatment for primary pulmonary coccidioidomycosis in patients who:
    • Are immunosuppressed (specifically those with depressed cellular immune function such as HIV/AIDS, TNF inhibitors, HSCT or solid organ transplant)
    • Have severe or significantly debilitating illness
    • Have diabetes or are frail because of age or comorbidities
    • Are pregnant
    • Are of African or Filipino ancestry
  • Disseminated coccidioidomycosis requires antifungal treatment.
  • Treatment is generally with an oral azole antifungal although amphotericin B is recommended for some groups. Primary care providers should consider consulting with specialists if considering initiating treatment.

See IDSA Practice Guidelines for the Treatment of Coccidioidomycosis for detailed treatment recommendations.



Valley fever patient information leaflet
  • There are no clearly effective interventions to prevent coccidioidomycosis for people living or working in endemic areas. Approaches to reduce the risk of inhaling fungal spores include staying inside with windows and doors closed when it is dusty outside, keeping car windows closed and using recirculating air conditioning while driving, and wearing an N95 mask if exposure to a high volume of dust cannot be avoided.
  • Patient education materials are available from the Los Angeles County Department of Public Health (DPH).
  • Employers whose staff are exposed when working in endemic areas should maintain a comprehensive approach to minimize dust, including the use of respiratory protection. Resources for Preventing Work-Related Valley Fever are available from the California Department of Public Health Occupational Health Branch.


Disease Reporting

Providers in California must report coccidioidomycosis within 7 calendar days from identification (Title 17, CCR, Section 2500). For cases in LA County:

For more information or questions regarding coccidioidomycosis, call the DPH Acute Communicable Disease Control Program at 213-240-7941.


Additional Resources


Reference Documents


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Table of Contents:

Clinical Presentation
Disease Reporting
Additional Resources
Reference Documents


Author Information:

Zachary Rubin, MD
Chief, Healthcare Outreach Unit

Acute Communicable Disease Control Program

County of Los Angeles
Department of Public Health

Rx for Prevention, 2023
Published: September 8, 2023