By Dr. Katherine Schlaerth, M.D.
Let’s say a patient comes in with a rash such as erythema nodosum or erythema multiforme, or even a red rash that does not have a clear explanation. There may be mid back pain, fever, chills, or night sweats. Perhaps there has been some weight loss. Muscle aches and joint pain may sound like influenza, but the flu test is negative. A cough or headache might also be present. Fatigue may show up as a noticeable drop in energy compared to what is normal for that person.
At that point, Valley Fever begins to enter the picture, along with many other possible diagnoses. So how do we identify it, or rule it out?
The first step is a careful history and physical exam. Travel and environmental exposure matter. Living in or spending time in a region like the Central Valley is already a major clue. We also look for factors that may increase the risk of more severe infection, such as steroid use, certain medications, or underlying medical conditions.
If there are signs that suggest pneumonia, such as lung findings or back pain, a chest X ray is usually needed. A localized infiltrate may first be treated as community acquired pneumonia. However, in areas where Valley Fever is common, it is often appropriate to test for Cocci at the same time, even if antibiotics are started.
If a patient has a severe or persistent headache lasting more than a couple of weeks, or if there are concerns that the infection may have spread beyond the lungs, more advanced testing may be necessary. This can include imaging such as MRI and procedures like a lumbar puncture to evaluate for meningitis.
Several blood tests can help identify Valley Fever.
Serologic testing looks for antibodies the body produces in response to the infection. A positive IgM or IgG test is generally considered diagnostic. However, timing matters. Early in the illness, tests can be negative even when the infection is present, so repeat testing may be needed if suspicion remains high.
Enzyme immunoassay testing is commonly used but can sometimes produce false positive or false negative results depending on the laboratory.
The complement fixation test is especially useful for following how a patient is responding over time. It helps clinicians monitor the course of the disease and is considered a valuable tool in ongoing care.
In regions like ours, certain laboratories are known for more reliable testing. The UC Davis laboratory and the Kern County Public Health Department lab are often trusted resources in what many call “Cocci country.”
Additional laboratory findings may support the diagnosis. These can include elevated inflammatory markers and, in some cases, an increased eosinophil count. Biopsy may also help identify the organism when needed.
Culturing the organism is possible but must be done under strict laboratory conditions, as even a single spore can pose a risk to laboratory personnel.
Because Valley Fever can spread beyond the lungs, further imaging may sometimes be required. This can include CT scans, bone scans, or MRI, depending on where symptoms are occurring. While joint pain is common early in the illness, new or localized bone pain should always be evaluated. The same is true for severe or persistent headaches.
Although Valley Fever most often begins in the lungs, it does not always stay there. The infection has a tendency to involve bone, particularly the spine, as well as the skin and the lining around the brain. In rare cases, it can appear in unexpected places, including the abdomen.
This is a reminder that no part of the body is completely off limits to this organism.
Despite all of this, most people who are exposed to Valley Fever will never know they had it. Some may experience only a few days of mild symptoms that feel like a slight flu and recover without testing or treatment.
However, for those who do become ill, especially in higher risk groups, early recognition and appropriate testing are important.
In a region like ours, diagnosing Valley Fever requires both clinical awareness and a healthy level of suspicion. For providers and community members alike, understanding when to consider Valley Fever can make a meaningful difference in care and outcomes.
Dr. Katherine Schlaerth is a physician and educator with board certifications in family medicine, pediatrics, geriatric medicine, and pediatric infectious diseases. She combines her clinical work with a strong commitment to medical education and mentorship. At Clinica Sierra Vista, she is especially passionate about teaching and guiding residents as they develop the skills needed to serve their communities. Dr. Schlaerth also completed a fellowship in Guatemala, bringing a global perspective to her work in patient care and training the next generation of physicians.
An accomplished author, her latest book, The Ways Our Bodies Age, delves into the science of aging. To learn more about her journey and her new book, read her full bio at the link below.
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Here are some ways you might qualify:
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This income limit is based on 185% of the Federal Poverty Level, and these amounts will be effective from April 1, 2025, to June 30, 2026.
Also, if you’re pregnant, the baby counts as part of your family size when figuring out if you qualify.
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