Valley fever is a fungal disease that occurs only in certain parts of the United States and South America. A person can only contract it by inhaling fungal spores.

It can lead to fever, chest pain, coughing, and some other symptoms.

Valley fever is caused by the fungus Coccidioides immitis (C. immitis), or by Coccidioides posadasii (C. posadasii). It is also known as coccidioidomycosis, California disease, desert rheumatism, and San Joaquin valley fever.

The fever does not pass between humans. An infected person will not transmit the disease to another person.

In the states where the fungus is active, there are 42.6 cases per 100,000 people every year, on average.

There are three different types of valley fever.

Acute valley fever

[Valley Fever most common in Arizona]Share on Pinterest
Valley Fever is most common in Arizona.

Initial symptoms are mild. Some people will have no symptoms at all, and they only know about the infection when they test positive during a skin or blood test.

The University of Arizona estimates that over 60 percent of infected people have either no symptoms or experience flu-like symptoms and never seek medical attention.

Signs and symptoms can appear approximately 1 to 3 weeks after exposure.

They may include:

  • chest pain – may be mild or quite severe
  • chills
  • cough
  • fatigue
  • fever
  • headache
  • joint aches
  • muscle aches
  • night sweats
  • shortness of breath

A skin rash can occur. This generally consists of spotty red bumps on the lower legs, which may be painful. Eventually, they become brown, known as erythema nodosum.

The rash may also appear on the back, arms, or chest. More rarely, it may produce blisters.

Individuals who are otherwise healthy will normally recover completely within 6 months.

In patients with severe symptoms, complete recovery may take up to a year. Fatigue and joint pains may persist for longer.

Chronic valley fever

Rarely, a patient with acute valley fever does not make a full recovery, and the condition progresses to a chronic form of pneumonia.

This is more likely in those with a weakened immune system.

Signs and symptoms include:

  • slight fever
  • weight loss
  • cough
  • chest pains
  • blood-stained spit (sputum)
  • lung nodules

Symptom severity may fluctuate between individuals and over time.

Disseminated valley fever

This is the most serious form of valley fever. It happens when the infection spreads from the lungs to other parts of the body through the bloodstream.

It can affect many organs, and particularly the skin, liver, brain, bones, meninges, and heart.

Signs and symptoms vary depending on which parts of the body are affected.

They may include:

  • skin lesions
  • skull lesions, which are often painful
  • lesions in the spine and other bones
  • swollen joints, which are usually painful
  • meningitis, or inflammation of the membranes around the brain and the spinal cord
  • muscle aches and stiffness
  • headaches
  • fever
  • neck or shoulder stiffness
  • change in mental status
  • photophobia, or sensitivity to light

Without treatment, it can be fatal.

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Valley fever is caused by a fungus found primarily in certain parts of the United States and northwestern Mexico.

A number of common factors increase the likelihood of contracting valley fever.

Geographical location: the risk is higher in areas where fungus spores are likely, such as Arizona, New Mexico, Texas, Utah, Nevada, and northwestern Mexico. If the person inhales the spores, they can become infected.

In these areas, people whose work involves disturbing soil have a higher risk. Examples are construction, excavation, agricultural work, or archaeological digging.

Ethnicity: Filipinos, Hispanic Amerindians, Native North Americans, and Asians have a higher risk of developing infections with symptoms, compared with Caucasians.

Pregnancy: in areas where valley fever is endemic, there is a higher risk of infection during the third trimester of pregnancy, and immediately after giving birth.

Diabetes: Individuals with diabetes who live in areas where valley fever exists have a higher risk of becoming infected, compared with other people in the same areas.

Weak immune system: People with a weakened immune system have a higher risk of infection and complications. This includes patients with HIV or AIDS, and those receiving steroid medications, chemotherapy, or immunosuppressant drugs. People with cancer may also be more susceptible.

Advanced age: older people are more likely to develop valley fever.


Valley fever is caused by a fungus, either C. immitis or C. posadasii.

The fungus grows as a mold in the soil. In this mold form, the fungus can survive for a very long time in harsh conditions, such as droughts, heat, or cold. It develops long filaments that break off and become airborne as spores. Breathing in the spores can lead to infection.

C. immitis and C. posadasii exist in alkaline desert soils, such as those found in northwestern Mexico, California’s San Joaquin Valley, Nevada, New Mexico, Texas, and Arizona. Valley fever also occurs in some parts of South and Central America.

A doctor cannot diagnose valley fever just by identifying the signs and symptoms, as these could indicate another illness, such as flu.

If the doctor suspects valley fever, specific diagnostic tests can check for coccidioides spherules, or cysts, in blood, tissue, or saliva.

Tests may include:

  • Sputum smear test: A sample of sputum is taken and tested for the presence of coccidioides. Sputum is coughed up or taken directly from the lungs, trachea, or bronchi.
  • Blood test: These will detect if there are antibodies against the fungus.

Other tests, such as the Polymerase Chain Reaction (PCR) urine test, are being looked at to help with diagnosis.


Most people do not need treatment for valley fever. Even in more severe cases, the best treatment is normally to rest and to consume a lot of liquids, as with a flu or cold.

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Valley fever can be difficult to diagnose given the similarity of its symptoms to other diseases.

However, the patient should be carefully monitored.

Antifungal medication may be prescribed if the patient:

  • has a weak immune system, due to cancer or cancer treatment, HIV or AIDs, or some other reason
  • has a severe or significantly debilitating illness
  • has diabetes or is frail because of other medical conditions or age
  • is pregnant
  • is of African or Filipino ancestry

Medications used to treat valley fever are fluconazole (Diflucan) and itraconazole (Sporanox).

Adverse effects may include:

In cases of serious infection, the patient may be administered amphotericin intravenously.

Although these antifungal medications control the fungus, they do not eliminate it. There remains a risk of relapse.

Complications are rare, but they may affect those in the higher risk groups.

They include:

  • pneumonia, which may be severe
  • ruptured lung nodules, or cavities in the lungs

Most of the nodules will go away, but some may rupture, resulting in severe chest pain and breathing difficulties.

The patient may need a tube inserted into the space around the lungs to remove the air. Sometimes surgery is required.

The most serious complication is when the disease becomes disseminated. The fungus spreads through the bloodstream to various parts of the body, and this can affect many organs.

The patient can develop skin ulcers, bone lesions, abscesses, severe joint pain, inflammation of the heart, problems with the urinary tract, and meningitis.

A study published in 2016 found that valley fever can worsen the symptoms of asthma, but that asthma does not make a person more susceptible to valley fever.