Valley fever is a fungal infection caused by coccidioides (kok-sid-e-OY-deze) organisms. It can cause fever, chest pain and coughing, among other signs and symptoms.
Two species of coccidioides fungi cause valley fever. These fungi are commonly found in soil in specific regions. The fungi’s spores can be stirred into the air by anything that disrupts the soil, such as farming, construction and wind.
The fungi can then be breathed into the lungs and cause valley fever, also known as acute coccidioidomycosis (kok-sid-e-oy-doh-my-KOH-sis). Mild cases of valley fever usually resolve on their own. In more severe cases, doctors prescribe antifungal medications that can treat the underlying infection.
The earliest recorded case of coccidioidomycosis was documented in Argentina in 1892, when a soldier was diagnosed with what was first thought to be an infection of coccidia parasitic protozoans, like cryptosporidium and toxoplasma, that infect the intestines of animals, including chickens, cows, dogs and cats. The soldier lived with the disease for 11 years, during which time his doctors realized it was not caused by a protozoa but by a fungus. The name, however, stuck.
In the 1930s, researchers identified the culprit as a soil fungus during a severe outbreak of coccidioidomycosis in the San Joaquin Valley of California, which also gave the disease its nickname of Valley Fever. During World War II, thousands of soldiers training in the Southwest contracted the disease, as did 22 Navy Seals training in Coalinga, Calif., in 2002.
Wildlife has also proven susceptible to the disease. In California, after the Jan. 17, 1994, Northridge earthquake triggered massive landslides in the Santa Rosa Mountains, the prevailing winds carried dust out to the Pacific coast where a population of sea lions, which had no previous exposure to the soil fungus and thus no immunity, was decimated by the disease.
People didn’t fare so well either after the quake. In Ventura County, Calif., which had seen only 52 cases of the disease during the entire previous year, more than 200 people contracted acute coccidioidomycosis between late January and mid-March and three people died.
Coccidioidomycosis is a disease of the American continents. It was first described in Argentina in the late 1800s, and most of what is known today was due to investigations made in the United States in the early 1900s. Currently, all countries in between have described cases of coccidioidomycosis, and most have recognized endemic areas.
The incidence of coccidioidal infections in other endemic areas of North and South America outside of the United States is unknown. The infection risk remains highest in the endemic areas of northern Mexico and Central and South America. However, the incidence over time may not mirror the increase seen in the southwestern United States, because the latter increase has been driven by construction and immigration of uninfected individuals into the area.
The prevalence of coccidioidomycosis in the Americas is as follow: 56% in Mexico, 42% in Guatemala, very low prevalence in Venezuela and Colombia, 26% in Brazil, 44% in Paraguay, and 40% in Argentina. In an endemic area of Brazil, coccidioidomycosis has been linked to hunting of armadillos.
The incidence of coccidioidomycosis outside of the Western Hemisphere is extremely low, but cases (primarily imported from California, Arizona, and Mexico) have been reported in the following countries:
- The Netherlands
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.
The life cycle of coccidioides
Many people who are exposed to the fungus Coccidioides never have symptoms.1 Other people may have flu-like symptoms that go usually away on their own after weeks to months. If your symptoms last for more than a week, contact your healthcare provider.
Symptoms of Valley fever include:
- Fatigue (tiredness)
- Shortness of breath
- Night sweats
- Muscle aches or joint pain
- Rash on upper body or legs
In extremely rare cases, the fungal spores can enter the skin through a cut, wound, or splinter and cause a skin infection.
Rashes on upper body
Complications are rare, but they may affect those in the higher risk groups.
- 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.
Diagnosis and test
Valley fever is difficult to diagnose solely on the basis of signs and symptoms, because they’re usually vague and overlap with symptoms that occur in other illnesses. Even a chest X-ray can’t distinguish valley fever from other lung diseases.
A definitive diagnosis depends on finding evidence of coccidioides organisms in tissue, blood or other body secretions. For that reason, you’re likely to have one or more of the following tests:
Sputum smear or culture: These tests check a sample of the matter that’s discharged while coughing (sputum) for the presence of coccidioides organisms.
Blood tests: Through a blood test, your doctor can check for antibodies against the fungus that causes valley fever.
Valley fever Treatment and medications
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.
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:
- Abdominal pain
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.
If you live in or visit areas where valley fever is common, take common sense precautions, especially during the summer months when the chance of infection is highest. Consider wearing a mask, staying inside during dust storms, wetting the soil before digging, and keeping doors and windows tightly closed.