Transmission

Coccidioidomycosis is caused when people inhale spores of the Coccidioides fungus. Coccidioides spores can become airborne when soil in endemic areas is disturbed, such as by winds or activities like construction, agricultural work, or digging. Certain occupations are particularly high risk, including wildland firefighting, construction, and other types of outdoor work. Documented outbreaks have also occurred among attendees of outdoor events in high incidence areas, including a music festival and a model airplane flying competition.

Even a single, brief exposure to dirt and dust in a high-incidence area can lead to infection. Although infections occur year-round in California, most patients are infected in the summer and fall, and present for care in the fall and winter.

Although rare, infection can also occur when spores enter through cuts or abrasions in the skin. Coccidioidomycosis is not transmitted directly from person to person, animal to animal, or between people and animals. ​

Respiratory illnesses (i.e., cough, fever)

• COVID-19
  

• Influenza
  

• Bacterial, viral, or other fungal pneumonia
  

• Acute respiratory distress syndrome​
  

Systemic illnesses (i.e., fever, night sweats, weight loss, lung/spine lesions)

• Tuberculosis
  

• Sarcoidosis
  

• Malignancy
  

Reviewing a patient's exposures (where they live, travel, or work), risk factors, and symptoms may help identify when coccidioidomycosis should be included in the differential diagnosis for a patient's illness. In addition, coccidioidomycosis symptoms can last longer than those of other acute respiratory infections, and concern for coccidioidomycosis may increase if a patient's respiratory symptoms are not resolving after 7-10 days or if they have not resolved following other treatments, such as antibiotics. ​​​

Diagnosis

When to suspect infection

Diagnosing coccidioidomycosis can be challenging because symptoms can look similar to other illnesses. Consequently, patients with coccidioidomycosis often experience delayed or missed diagnoses, which may be associated with worse health outcomes.

Healthcare providers in California should have increased clinical suspicion of coccidioidomycosis if they are caring for a patient who:

• Presents with over 7-10 days of respiratory illness, such as pneumonia, especially if they test negative for other common respiratory illnesses or fail to improve

• Lived, worked, attended school, or traveled in an area with high incidence of Valley fever or an area where Valley fever is expanding in the months before onset

• Has been around outdoor dirt or dust in an area where Valley fever is common, particularly as part of outdoor work activities such as construction, agriculture, or wildland firefighting
  

Many of these risk factors can be identified by taking a thorough social history, including gathering details about residence, occupation, school attendance, and recent travel in high-incidence areas.​​​​​

Imaging findings in coccidioidomycosis

Healthcare providers often order chest X-rays or CT scans in patients with prolonged respiratory symptoms to evaluate for pneumonia or other underlying causes. It is important to recognize that coccidioidomycosis can have a variety of appearances on chest imaging, including findings that mimic bacterial, viral, or other fungal pneumonias, tuberculosis, sarcoidosis, malignancy, and other diseases. Imaging in a patient with coccidioidomycosis could show:

• No focal lesions

• Localized infiltrates

• Bilateral or multifocal infiltrates

• Single nodules with or without adenopathy

• Cavitary lesions
  

• Pleural effusions

• Discrete lung masses

  
  

Imaging examples

• Chest radiographs: lingular and bilateral multifocal consolidations; CT scans: lung nodules and pleural effusions – Jude et al. RadioGraphics 2014.

• X-ray: left lower opacity; CT scan: left lower lobe consolidation – Fayed et al. J Fungi 2024.

• CT scans: lung masses – Fayed et al. J Fungi 2024.

• CT scans: left upper lobe and right lower lobe cavitary lesions – Fayed et al. J Fungi 2024.
  

• CT scan: left upper lobe nodule – Fayed et al. J Fungi 2024.​
  

Laboratory testing

Enzyme immunoassay (EIA), immunodiffusion (ID), and complement fixation (CF) tests are the most used coccidioidomycosis serologic (antibody) tests and are typically performed at a clinical or public health laboratory. These tests have variable sensitivities and specificities which can make interpretation challenging. If you order serologic tests to detect Coccidioides IgM and IgG antibodies, please consider the following: 

• A patient with a positive Coccidioides IgM OR IgG (or both) could have acute coccidioidomycosis.

• A negative antibody test does not necessarily rule out coccidioidomycosis. This can be for a number of reasons including:​​
  

• Antibody development may lag illness onset by several weeks due to a variety of factors, including the timing and level of exposure and patient immune status;

• Variable test sensitivity of diagnostic test used
  

• A negative result from one test type does not necessarily invalidate a positive result from another test type, and not all patients with coccidioidomycosis will have a detectable CF titer.

• If there is high clinical suspicion of coccidioidomycosis, clinicians can consider repeating serologies 2-4 weeks later or utilizing histopathology, polymerase chain reaction (PCR) testing, or culture. ​
  

• Cases of severe coccidioidomycosis have been identified with positive cultures but negative serologies. For patients hospitalized with suspected coccidioidomycosis, PCR and culture of tissue or respiratory specimens should be considered if serologies are negative.  ​​​
  

• Culture or histopathology may be used on respiratory secretions, tissue biopsies, or normally sterile body fluid samples (i.e., pleural, peritoneal, cerebrospinal fluid, blood, abscess material).​​

• If​ the Coccidioides spherule is detected by histopathology or if septate hyphae with barrel-shaped arthroconidia were observed by microscopic examination, this is diagnostic for coccidioidomycosis.

• Culture growt​h may take up to a week, and given the infectious risk, processing and manipulation of cultures should be done in a biosafety level 3 laboratory.  ​
  

Testing algorithm

CDC has developed a clinical testing algorithm for coccidioidomycosis to help guide diagnoses:

​

​

Download Image​ | PDF

Management

​While not all patients with coccidioidomycosis need treatment, early and ongoing monitoring of patients for signs of severe disease is vital to prevent poor outcomes. Patients may need to be monitored for several months or more; signs may include worsening respiratory illness or progression to skin, bone/joint disease, or meningitis.​

Antifungal medications are available and suggested for use in patients with progressive or severe disease. Some patients can develop long-term infections in the lungs or other parts of the body, such as in the bones or joints, that may require treatment for months to years, and, in rare cases, may require surgery. Patients with coccidioidal meningitis will need to be treated with medication for the rest of their lives.

While most patients with coccidioidomycosis who recover are likely protected from acquiring infection again, relapse or worsening of disease can occur if a patient becomes immunocompromised. 

Please consult IDSA for best practices in clinical management: IDSA Clinical Practice Guideline for the Treatment of Coccidioidomycosis

Reporting

Healthcare providers and laboratories are required to report cases of coccidioidomycosis to the local health department (LHD) within one week (seven calendar days) of identification or within one working day (24 hours) if an outbreak is suspected.

Healthcare providers are a key resource for detecting outbreaks, as California coccidioidomycosis surveillance is entirely laboratory-based and does not contain any information on patients' potential exposures or clinical manifestations. Common exposures, and by extension, potential outbreaks, are often identified by providers, employees in high-risk occupations, or whistleblowers. Previous outbreaks have been associated with outdoor work, including construction and wildland firefighting, and with outdoor events, including a music festival and a model airplane competition. If you are caring for a patient(s) with coccidioidomycosis who may have a shared exposure that caused their illness, please report this to your local health department in case it merits a public health investigation.