Valley fever overview
Valley fever is a disease caused by a fungus that gets into your body through your lungs. It can make you feel like you have a cold or the flu and may cause a rash. Most people get better without treatment.
But if your body’s natural defense system (immune system) is weak, valley fever can be deadly. In rare cases it can be deadly even for people with a normal immune system. Valley fever can spread from your lungs to other parts of your body. Those at higher risk for severe illness include pregnant women, people who have HIV infection, people who take medicines that weaken the immune system, and people who have diabetes. Filipinos, African Americans, Mexican Americans, and Native Americans also have a higher risk of dying from valley fever.
Valley fever occurs in dry desert areas of the southwestern United States, central California, and Mexico. It also occurs in dry areas of Central and South America.
Valley fever is also called desert fever, San Joaquin Valley fever, coccidioidomycosis, and desert rheumatism.
What are the symptoms and signs of valley fever?
About 60% of all infected people (without immunosuppression) have no symptoms and do not seek medical care. About 30%-35% of people who develop symptoms have flu-like symptoms (fever, cough, malaise, and chills) that resolve over about two to six weeks without treatment. Some may develop additional symptoms such as shortness of breath, night sweats, headaches, sputum production, and joint and muscle pains (symptoms resembling pneumonia). Women, more often than men, may develop erythema nodosum (reddish, painful, tender lumps, usually on the legs) or erythema multiforme (an allergic reaction similar to erythema nodosum in multiple body sites with rash). Usually these symptoms resolve in about two to six weeks.
Chronic coccidioidomycosis occurs in about 8% of patients and is characterized by the above symptoms but may spread from the lungs to other parts of the body. People develop lung cavities that may disappear in about two years or become calcified.
Progressive pulmonary coccidioidomycosis includes the above symptoms but progresses to lung volume loss, fibrosis (scarring), and inflammation, considered serious complications of the disease.
Disseminated coccidioidomycosis (about 1% of cases) can be characterized by the above symptoms, but they may occur over weeks to years. The fungi may be found in any organ system but are most frequently seen in the skin, meninges, and bones. In a few individuals, the disease is rapidly fatal. Disseminated disease occurs most often in immunosuppressed individuals, males, and pregnant females.
Other mammals, like dogs, can become infected. As many as 28% of dogs by the age of 2 years may have had the disease, with about 6% showing symptoms of cough, shortness of breath, decreased appetite, and listlessness. The animals are not contagious to each other or humans, but like in some humans, the disease may progress.
Causes of valley fever
The fungi that cause valley fever Coccidioides immitis or Coccidioides posadasii thrive in the arid desert soils of southern Arizona, Nevada, northern Mexico and California’s San Joaquin Valley. They’re also endemic to New Mexico, Texas, and parts of Central and South America areas with mild winters and arid summers.
Like many other fungi, coccidioides species have a complex life cycle. In the soil, they grow as a mold with long filaments that break off into airborne spores when the soil is disturbed. The spores are extremely small, can be carried hundreds of miles by the wind and are highly contagious. Once inside the lungs, the spores reproduce, perpetuating the cycle of the disease.
Risk Factors of valley fever
- Environmental exposure. Anyone who inhales the spores that cause valley fever is at risk of infection. Some experts estimate that up to half the people living in areas where valley fever is common have been infected. People who have jobs that expose them to dust are most at risk construction, road and agricultural workers, ranchers, archeologists, and military personnel on field exercises.
- Race. For reasons that aren’t well understood, Filipinos, Hispanics, blacks, Native Americans and Asians are more susceptible to developing serious infection with coccidioidomycosis than are whites.
- Pregnancy. Pregnant women are vulnerable to more serious coccidioidomycosis during the third trimester, and new mothers are vulnerable right after their babies are born.
- Weakened immune system. Anyone with a weakened immune system is at increased risk of serious complications. This includes people living with AIDS or those being treated with steroids, chemotherapy or anti-rejection drugs after transplant surgery. People with cancer and Hodgkin lymphoma also have an increased risk.
- Age. Older adults are more likely to develop valley fever. This may be because their immune systems are less robust or because they have other medical conditions that affect their overall health.
How is valley fever diagnosed?
Early in the disease, the diagnosis is difficult because the symptoms may be mild so no tests are initiated. Accurate diagnosis of coccidioidomycosis is important because there are many diseases that have similar initial symptoms and may occur in areas of the world where coccidioidomycosis occurs; for example, Andes virus (caused by a hantavirus), arbovirus encephalitis (caused by six different viruses), Argentine hemorrhagic fever (an arenavirus infection caused by Junin virus), cryptococcosis (caused by Cryptococcus neoformans, a fungal species), and others. Fortunately, a confirmative diagnostic test is easily done by microscopic examination of sputum or a tissue biopsy. The biopsy shows characteristic fungal spherules and endospores of Coccidioides immitis or Coccidioides posadasii. These fungi can also be identified after they are cultured on fungal media (growth takes about five days). Additionally, there are several serum tests and a PCR test (to detect the genetic material of the fungus) that are available. High blood levels of IgG (an immunoglobulin) that react with the fungi can help determine the extent of the disease. Skin tests can determine if the person has been exposed to the fungi, but the test is not very specific or sensitive.
Other tests help determine the extent of the disease. The most frequent test is a chest X-ray to identify abnormalities in the lungs. MRI and CT scans are used to examine brain or other organ (especially bone) involvement. Bone scans also help to determine the presence of bone involvement. Most physicians will do other routine blood tests such as a CBC (complete blood count) and ESR (erythrocyte sedimentation rate, a marker of inflammation) test.
Occasionally, the diagnosis may require obtaining samples of tissue or tissue fluid, so lumbar puncture, bronchoscopy, and surgical or needle biopsy may be done.
Treatments and drugs for valley fever
Most people with acute valley fever don’t require treatment. Even when symptoms are severe, the best therapy for otherwise healthy adults is often bed rest and fluids the same approach used for colds and the flu. Still, doctors carefully monitor people with valley fever.
If symptoms don’t improve or become worse or if you are at increased risk of complications, your doctor may prescribe an antifungal medication, such as fluconazole. Antifungal medications are also used for people with chronic or disseminated disease.
In general, the antifungal drugs fluconazole (Diflucan) or itraconazole (Sporanox, Onmel) are used for all but the most serious forms of coccidioidomycosis disease.
All antifungals can have serious side effects. However, these side effects usually go away once the medication is stopped. The most common side effects of fluconazole and itraconazole are nausea, vomiting, abdominal pain and diarrhea.
More serious infection may be treated initially with an intravenous antifungal medication such as amphotericin B (Abelcet, Amphotec, others).
These medications control the fungus, but sometimes don’t destroy it, and relapses may occur. For many people, a single bout of valley fever results in lifelong immunity, but the disease can be reactivated, or you can be reinfected if your immune system is significantly weakened.
Can valley fever be prevented?
Research is progressing at several laboratories, but to date there is no vaccine available to prevent coccidioidomycosis in humans. People who live in endemic areas (see map in the last Web citation) of California, Arizona, New Mexico, and Texas are likely to be exposed to the organisms since they occur in soil and dust. People who are more susceptible to the disease (for example, immunosuppressed people such as those with HIV/AIDS or cancer, the elderly, and pregnant females) should avoid new construction sites and stay indoors on dusty days. Soil in these areas can be moistened to prevent dust formation, and some investigators suggest that susceptible people should wear dust masks if dust exposure is likely. People who get the disease usually develop immunity to it, and unless their immune system is compromised, will not get the disease again.
Is valley fever contagious?
Valley fever is not contagious person to person. People only become infected when they inhale arthroconidia (spores) of Coccidioides that settle in the lungs. Spores are easily disturbed and become airborne mixed with dust, especially on dusty, windy days and in areas where soil has been recently disturbed by construction or similar actions.