What Is Coccidiodomycosis (Valley Fever)?

Coccidioidomycosis is a fungal infection caused by Coccidioides immitis or Coccidioides posadaii. It is commonly known as "Valley fever." The infection usually affects the lungs.

Coccidioidomycosis is most common in parts of the Southwestern United States, from Texas to southern California. It is also common in northern Mexico, Central America, and South America. When it spreads beyond the lungs, it is considered an AIDS-defining illness. These are diseases that are associated with advanced HIV infection.

This article looks at coccidioidomycosis, its symptoms, causes, and diagnosis. It also discusses the ways in which this condition is treated, and how you might be able to prevent it.

Coccidioidomycosis Symptoms

Most people with coccidioidomycosis will not have symptoms. This is because a healthy person's immune system is usually strong enough to control the infection. When symptoms do appear, the most common tend to be mild and flu-like, including:

• Fever
• Headache
• Cough
• Fatigue
• Chest pain
• Chills
• Shortness of breath (dyspnea)
• Muscle pain (myalgia)
• Joint pain (arthralgia)
• Rash on the upper body or legs

In the southwestern United States, coccidioidomycosis is a common cause of community-acquired pneumonia, or pneumonia that is acquired outside of a hospital.

If the fungus spreads beyond the lungs, it is called disseminated coccidioidomycosis. Disseminated disease can affect multiple organ systems. Complications can include:

• Skin ulcers and abscesses
• Swollen and painful joints
• Bone lesions
• Heart inflammation (myocarditis)
• Difficulty urinating
• Meningitis, which is fatal if untreated

Approximately 5% to 10% of people who get Valley fever will develop serious or long-term problems in their lungs.

What Causes Valley Fever

The Coccidioides fungus is present in the soil and can produce airborne spores during the rainy season. You can become infected when you inhale the spores. This usually happens without your knowledge.

The spores can multiply and create nodules in the airways. In people with weakened immune systems, especially people with AIDS, this can lead to a severe lung infection. When the immune system isn't able to stop the fungus, it can spread to the blood. This can lead to disease in distant organs.

Coccidioides cannot be passed from person to person.

How Common Is Valley Fever?

In 2019, 18,407 cases of Valley fever were reported to the Centers for Disease Control and Prevention (CDC). The majority of infections occur in Arizona and California. In Phoenix and Tucson, for example, Valley fever causes an estimated 15% to nearly 30% of community-acquired pneumonia. Low testing rates, however, suggest it is probably under-recognized.

On average, there were approximately 200 coccidioidomycosis-associated deaths each year in the United States between 1999 and 2016. The incidence and severity has decreased in people with HIV due to the widespread use of antiretroviral therapy.

Diagnosing Coccidioidomycosis

Coccidioidomycosis can be diagnosed with a number of different tests, including:

• Microscopic examination: This looks at body fluids such as sputum or tissue samples.
• Microbial cultures: Samples are used to grow the fungus in the laboratory. This can help provide evidence of its presence in the lungs.
• Blood tests: These tests detect immune proteins called antibodies produced by the body in response to the infection.
• Polymerase chain reaction (PCR) test: This lab test can identify the fungus by finding and copying small amounts of its DNA.
• Chest X-rays: These imaging tests may be used to support the diagnosis.

How Valley Fever Is Treated

For people with an intact immune system, coccidioidomycosis usually doesn't require treatment. Supportive care like pain relievers and bed rest are usually enough to manage the infection.

For less-severe cases of coccidioidomycosis, Diflucan (fluconazole) is the most frequently prescribed oral antifungal drug. This is because it is usually well-absorbed, has fewer drug interactions, and is less expensive compared to other options.

Antifungal therapy should be considered for pregnant people, however, treatment depends on the stage of pregnancy. 

For the severely ill, the antifungal Fungizone (amphotericin B) is the drug of choice. This drug is delivered intravenously until the infection is under control. Even after recovery, patients need lifelong oral antifungals to prevent recurrence.

People with Coccidioides-related meningitis can also receive Fungizone, but it is administered intrathecally. This means it is injected into the space surrounding either the brain or spinal cord.

Prevention

It is difficult to prevent coccidioidomycosis in areas where the fungus occurs naturally. Even for people with severely compromised immune systems, preventive antifungal therapy is not recommended. Yearly or twice-yearly testing, however, is a good idea. No vaccines are available to prevent coccidioidomycosis.

If you think you are at risk and you live in an area where the fungus is common, there are a few precautions you can take.

Summary

Coccidioidomycosis is caused by a fungus that is common in the Southwestern United States. Most people with coccidioidomycosis don't develop symptoms. When symptoms do appear, they tend to be mild and flu-like. 

People who have weakened immune systems may develop serious illness such as pneumonia. The infection can also spread outside the lungs and affect multiple organs. 

The condition is usually treated with antifungal medications. Some people may need to take these medications long-term to prevent recurrence.

A Word From Verywell

Coccidioidomycosis, also known as Valley fever, poses the biggest threat to people with compromised immune systems. This is especially true for people who have HIV.

The symptoms of Valley fever may be mild and flu-like. Most people don't need treatment as their immune systems can fight the disease. For those who do need treatment, oral antifungals are generally the first line of response. Speak with your healthcare provider if you are experiencing symptoms or if you are concerned about your susceptibility to coccidioidomycosis.