Coccidioides imitis is a soil fungus that requires alkaline soil to grow. It is found in arid regions from California to Texas and in areas of Central and South America. It causes “Valley Fever”, which can mimic the flu, but is not contagious from person to person.
Coccidioides infection begins when animals or people inhale its arthroconidia. These are the soil form of the organism, usually found in the top four inches of desert soil.
Tourists passing through the Southwestern US may inhale large numbers of infectious arthroconidia.
When they reach the lungs, they grow and form spherules, the next stage in the Coccidioides life cycle.
Our immune response to the fungal infection can result in fatigue, fever, cough, chest pain, headaches, rash, nightsweats, muscle pain, joint aches, weight loss and poor appetite.
These are the symptoms of Valley Fever.
Valley Fever spherules in our tissues soon become surrounded by layers of white blood cells. Since the white blood cells can’t kill the fungus, they try to wall it off.
Each granuloma is like an onion, with multiple layers of immune response cells surrounding its core of Coccidioides spherules.
Pathologists can use a microscope to see these granulomata and spherules in a tissue biopsy, allowing them to diagnose the fungal infection. Serology tests for Coccidioides are available, too, but may be unreliable in certain patients.
Doctors may have problems diagnosing Coccidioides infection, especially in areas where the fungus does not reside.
Even with a relatively strong immune system, tissue destruction and lung cavity formation can occur from Coccidioides infection.
Theis patient has a left lung cavity (hole eaten in lung tissue) from the fungal infection.
Radiologists can turn up the contrast on CT scan images to better see the extent of Coccidioides lung disease.
(Compare upper to lower image)
The fungal lung infection can affect the adjacent pleural membranes, pericardium and even the heart itself.
Bacteria from the mouth can find their way into a Cocci cavity, forming an abscess. This can cause high fevers, chest pain and malaise. Coccidioides infection can cause lung scarring, shrinking the involved lung. This patient’s diaphragm is pulled up into a “tent” or peak from scarring near the cavity.
Pus that breaks out of a lung cavity into the adjacent pleural space forms an empyema.
Empyemas require a thoracostomy tube for drainage.
If the empyema fluid is too thick to be removed by tube, surgical drainage is required for resolution.
Video Assisted Thoracoscopy or open thoracic surgery are used to remove the pleural “peel” (the “peel” forms from severe inflammation and pus remaining in the pleural space for weeks or months).
Someone with a weak immune system may die from disseminated infection (when Coccidioides spreads out of the lungs to involve the brain, bones, skin or other sites).
Patients with emphysema, diabetes, cancer chemotherapy, ongoing pregnancy or other immunosuppressive problems are more prone to severe disease with Coccidioides fungus.
Persons of Filipino, Polynesian and African ancestry can also suffer severe problems with the infection. Their immune systems are less effective in controlling the fungus.
Patients with disseminated disease are unable to contain the fungus. Involvement of brain, bones, abdominal viscera, muscles and soft tissues can be life-threatening. Most cases of disseminated Coccidioides are fatal without treatment.
Coccidioides fungus can activate the immune system, causing rashes of all sorts.
Joint pain, fatigue, red eyes, ulcers in the mouth and swelling of the lips and tongue can all be present with the rash.
Erythema multiforme is a flat or somewhat raised rash of doughnut or ring-shaped lesions that have a red or purple color. The rings may be clearly evident as in the photo above, or less obvious, as seen below.
The rash, joint aches, lip and tongue swelling, fatigue and red eyes usually resolve promptly on treatment for Coccidioides infection. These rashes and other symptoms occur from immune system activation by the fungus.
Erythema nodosum is a different sort of skin inflammation than erythema multiforme. It consists of large tender nodules beneath the skin. These usually occur on the front of the legs, but they can appear anywhere on the body in patients with Coccidoides infection. No Coccidioides fungus is found in these lesions; they are due to immune system stimulation by the infection.
Coccidioides therapy may include the different classes of anti-fungal drugs shown above.
Azoles are commonly used in patients able to take oral therapy (fluconazole, itraconazole, voriconazole, posaconazole).
Echinocandins are less easy to use outside of a hospital, since they are given intravenously.
Amphotericin B formulations are also intravenous, and are usually given to more seriously ill patients.
For more information about Valley Fever, visit
Valley Fever Center for Excellence website.