Valley Fever Testing: How Diagnosis Works and When to Ask

Valley fever is diagnosed mostly with a blood test that looks for antibodies to the Coccidioides fungus. Your provider may also order a chest X-ray, a PCR test or a culture of a respiratory sample. The catch is timing. A test taken too early can come back negative even when you are infected, so a single negative result does not always close the question. If you live in or have visited the San Joaquin Valley and a “pneumonia” is not clearing up, this guide explains what the tests are, how to read the results, and how to get your blood drawn without losing a day to it.

TL;DR

• Valley fever (coccidioidomycosis) is usually confirmed with a blood test for IgM and IgG antibodies, often an enzyme immunoassay (EIA) screen. PCR and culture are used on respiratory specimens in some cases.
• Antibodies take weeks to appear, so early tests can be negative and may need repeating.
• If antibiotics for pneumonia are not helping, ask your provider to consider a fungal cause, and mention any time you spent in the Central Valley or another endemic area.
• Valley fever is not contagious. Not everyone needs treatment.
• EIV Diagnostics, an independent pathology laboratory in Fresno, offers self-pay testing and mobile phlebotomy from $65 per visit. Call us to confirm the specific test you need.

Table of Contents

• What valley fever is, and why testing matters here
• When it makes sense to get tested
• The main valley fever tests
• Why a negative result is not always the end
• How long it takes to get an answer
• Getting tested without a doctor’s visit
• Getting your blood drawn at home or at work
• A note on treatment
• Our perspective: what we see from the lab side
• Ordering with EIV Diagnostics
• Questions people ask about valley fever testing
• Sources

What valley fever is, and why testing matters here

Valley fever is a lung infection caused by breathing in spores of Coccidioides immitis or Coccidioides posadasii, fungi that live in desert and semi-arid soil. Mayo Clinic lists parts of Arizona, California, Nevada, Utah, New Mexico, Texas and Washington as endemic areas. The San Joaquin Valley, where Fresno, Clovis, Madera, Visalia, Hanford and Reedley sit, is one of the best-known hot spots in California.

The fungus lives in soil as a mold. Once inhaled, it changes form inside the lungs into structures called spherules, and that is when infection begins. Digging, farm work, construction, wind-blown dust and wildfire-season dust are the usual exposures, but you do not have to do anything unusual. Breathing is enough.

The CDC reports that about 40% of infected people develop lung symptoms. Most infections are self-limiting, and 5% to 10% develop complications. Disseminated disease, where the fungus spreads beyond the lungs to skin, joints, bones or the brain’s lining, is rare but serious.

Testing matters because valley fever looks like so many other things. Cough, fever, fatigue, shortness of breath, chest pain, night sweats, joint aches and sometimes a rash all overlap with flu and bacterial pneumonia. The CDC notes that valley fever often presents as community-acquired pneumonia in primary and urgent care and cannot be reliably told apart from other causes without testing.

When it makes sense to get tested

The CDC’s guidance for patients is simple: if you are taking antibiotics for pneumonia and not getting better, ask your doctor about valley fever. That matters because antibiotics do not work on a fungus. Clinical sources describe a pattern in which patients are given antibacterial drugs first, sometimes more than once, before anyone considers a fungal cause.

Consider asking for testing if you have:

• A cough, fever, fatigue or chest pain lasting more than a week or two, especially if a first course of antibiotics did nothing
• Night sweats, unexplained joint pain or a new rash along with respiratory symptoms
• Lived in, worked in or traveled through the Central Valley or another endemic region, even weeks before symptoms started

The IDSA guideline gives the usual incubation period for early coccidioidal syndromes as 1 to 4 weeks, so the exposure may be further back than you think. Always tell your provider about travel, even if it was a month ago.

See a healthcare provider promptly if you have trouble breathing, a high fever that will not break, severe headache or stiff neck, or skin lesions, bone pain or swollen joints with a lingering cough. Mayo Clinic advises seeking care for symptoms if you are older than 60, pregnant, have a weakened immune system, or are Filipino or African. Those groups face higher risk of severe disease. In an emergency, call 911.

The main valley fever tests

There is no single test that answers every question. Providers pick from a short list depending on how long you have been sick and what sample they can get.

The blood test (serology)

This is the test most people mean by “valley fever blood test.” The CDC states that serologic tests detect IgM and IgG antibodies, and that enzyme immunoassay is the most common screening method. A positive screen is often followed by confirmatory tests that also give a titer, a number showing how concentrated the antibodies are. Your provider may track that number over time.

The blood draw itself is routine: one venipuncture, a few minutes, no fasting. Your provider may order several valley fever antibody tests at once, since results can differ between methods.

PCR and culture

PCR detects fungal DNA and can be useful on respiratory samples. Culture is the gold standard in principle, but the Mayo Clinic team working on a faster test points out that many patients have dry, non-productive coughs and cannot give a usable sample. Handling Coccidioides cultures also requires a biosafety level 3 laboratory, which is why culture is rarely done at the point of care. If your lab asks for a sputum sample, tell the staff what you suspect so the specimen is handled correctly.

Tissue and skin findings

Sometimes valley fever shows up first on the skin, as a rash, nodules or a non-healing lesion. In those cases a dermatologist may take a biopsy, and a pathologist looks for the fungus in the tissue. This is where subspecialty pathology review can speed up an answer.

Why a negative result is not always the end

This is the part patients most often misunderstand. Antibodies take time to develop. The IDSA guideline explains that serologic tests can be negative in early active infection, and that clinicians often rely on clinical suspicion and repeat testing over the following weeks instead of one negative report.

In practice that means:

1. Test when symptoms have lasted long enough. Testing in the first days of illness is the likeliest to miss infection.
2. Repeat if symptoms continue. A second sample a few weeks later may turn positive.
3. Do not stop at one result. If the test is negative but you are still sick, go back to your provider rather than assume you are in the clear.

A Tucson news report on a self-order test from a regional laboratory quoted a clinical microbiologist saying that early testing often produces false negatives, and that people who want their own test should have had symptoms for some time first. That fits what the IDSA says.

Antibody levels also change with the course of illness. Unlike many infections where IgG stays positive for life, anticoccidioidal antibodies typically return to negative as the infection resolves, per the same IDSA guideline. A negative result years after recovery is therefore not surprising.

How long it takes to get an answer

Speed is the weak point of valley fever diagnosis. Mayo Clinic researchers describe a median of 23 days from first care to diagnosis, often over several visits that cost patients time, transportation and childcare. They are developing a rapid test that could one day give an answer at the first visit. That test was still in development when Mayo posted the story in 2025, so do not count on it yet.

What you can control today is the logistics: getting the order, getting the draw done quickly, and getting results back to your provider. Much of the 23 days is lost between steps, not in the lab itself.

Getting tested without a doctor’s visit

Many people in the Valley have a story like this: a month of cough, one urgent care visit, a Z-pack, no answer. If your provider has not tested you, you have two sensible options.

1. Go back and ask by name. Say “I live in the Central Valley, and I want to be tested for valley fever.” Bring up your travel and work exposure.
2. Order your own lab test. Some laboratories sell tests directly to patients who pay out of pocket, with no prescription. EIV Diagnostics runs a self-pay testing program for patients who want to order tests without a doctor’s order, as well as for patients who have a prescription.

Self-ordering has a limit. A lab result is not a diagnosis. Whatever the number says, you need a clinician to interpret it alongside your symptoms and imaging, and to decide on treatment. If a result is positive, or negative but you remain unwell, take it to your provider or an urgent care clinic the same week. If you have no primary care provider, a community health center or urgent care can review the result.

Getting your blood drawn at home or at work

A 20-minute draw is not the hard part. The hard part is the drive, the wait and the time off, especially if you are feeling run down with a lingering lung infection. That is why we built mobile phlebotomy into our service. A trained phlebotomist comes to your home or office in the Fresno area, collects the sample and brings it to our laboratory.

Mobile phlebotomy at EIV Diagnostics starts at $65 per visit. We serve Fresno, Clovis, Madera, Sanger, Reedley, Kingsburg, Kerman, Visalia, Tulare, Hanford and Lemoore, across Fresno, Madera, Tulare and Kings counties. It helps most when:

• You are too tired or short of breath to sit in a waiting room
• You have a repeat test coming up in a few weeks and want to skip another trip
• You are a caregiver, a shift worker or a small employer who cannot lose half a day
• A provider has ordered several tests and wants them drawn together

We can only draw the tests that have been ordered, either by your provider or by you through self-pay. Tell us which test you need when you book so we can confirm availability and prepare the right tubes.

A note on treatment

A positive test does not always mean medication. According to the IDSA guideline, many uncomplicated lung infections resolve without antifungal therapy. Drugs such as fluconazole or itraconazole are prioritized for people at higher risk of spread: those who are immunosuppressed, pregnant, have severe lung disease, or are of African or Filipino ancestry. Clinicians weigh the risk of severe illness against the side effects of long antifungal courses.

That decision belongs to your physician, ideally one who treats valley fever often. An infectious disease specialist or pulmonologist is a reasonable referral if your case is complicated. Do not start or stop antifungal medication on your own.

Two more points people ask about:

• You cannot catch it from someone else. Valley fever is not contagious. It does not pass between people, or from animals to people.
• Reducing exposure still helps. In dusty conditions, workers can follow employer safety guidance, and the CDC has a page on reducing risk for outdoor and construction work.

Our perspective: what we see from the lab side

We are an independent pathology laboratory in Fresno, so valley fever is not an abstract topic for us. It is part of the daily backdrop of medicine in the Central Valley. Here is how we think about it.

Speed comes from the whole chain. A fast assay does not help if the patient needs three trips to get a draw. That is why we pair board-certified pathologists and rapid turnaround with mobile phlebotomy. The shortest path to an answer is one that the patient can actually complete.

A lab result needs context. Serology, PCR, histopathology and imaging each cover a different part of the picture. Subspecialty pathology review matters most when the picture is unclear, for example a skin lesion that might be fungal, or a tissue sample from a lung nodule.

Patients should be allowed to ask. Some people feel brushed off after a negative test or a quick pneumonia diagnosis. Self-pay testing exists so you can get data in your own hands. We still encourage you to take it to a clinician, because treatment decisions are not ours to make for you.

Providers are our partners in this. For physicians in Fresno, Madera, Tulare and Kings counties, we offer clinical pathology, molecular pathology, dermatopathology and digital pathology, supported by CAP-accredited quality standards. When a case does not fit the usual pattern, a second pair of expert eyes is worth having.

— EIV Diagnostics

Ordering with EIV Diagnostics

If you are a patient, start on our self-pay page or call us to ask about the test you need, and add mobile phlebotomy if you would rather be drawn at home or work. If you are a provider, see our clinical pathology services and our molecular pathology and dermatopathology pages, or browse the full list of services. Prices other than mobile phlebotomy are not published, so ask us for a quote before you book.

Questions people ask about valley fever testing

Is there a blood test for valley fever?

Yes. It measures IgM and IgG antibodies against Coccidioides, and enzyme immunoassay is the most common screening method, according to the CDC. Results can be negative early in the illness, so your provider may repeat it.

Can I get a valley fever test without a doctor’s order?

Some laboratories sell tests directly to patients who pay out of pocket. EIV Diagnostics offers self-pay testing, and you can call us to confirm what is available for valley fever. A positive or confusing result still needs a clinician to interpret it.

How long after exposure should I test?

Symptoms usually begin one to four weeks after exposure, per the IDSA. Testing makes sense once you have symptoms that persist. If you test very early and it is negative, ask your provider whether to repeat it in a few weeks.

What is disseminated coccidioidomycosis?

It is a rare complication in which the fungus spreads from the lungs to other parts of the body, such as skin, joints, bones or the central nervous system, as the CDC describes. It is treated with long-term antifungal therapy under a physician’s care.

Is valley fever contagious?

No. You get it by inhaling spores from soil, not from another person or an animal, per Mayo Clinic.

Sources

• Clinical Overview of Valley Fever, CDC
• Testing Algorithm for Coccidioidomycosis, CDC
• Testing for Valley Fever, CDC
• Valley Fever, CDC
• IDSA 2016 Clinical Practice Guideline for the Treatment of Coccidioidomycosis
• IDSA 2016 Guideline (PDF)
• Valley fever, symptoms and causes, Mayo Clinic
• Faster diagnosis for valley fever: new test in development, Mayo Clinic News Network
• For $35, you can find out if you have valley fever, without going to a doctor, Arizona Daily Star