The Mysterious Fungus Infecting the American Southwest | The Atlantic Magazine


Microscopic appearance of Coccidioides immitis

(Medscape/Thomas Matthew)

Here’s a very interesting story from The Atlantic magazine. It’s about an important fungus found in great abundance in Arizona, but not one that will be seen on a mushroom club foray.

The pathogenic fungal species Coccidioides immitis and its close relatives are endemic in our soil, growing in the form of a hyphal mycelium. It does not produce any visible terrestrial fruiting body, but sporulates underground. The spores are dispersed when dust is kicked up from desert lands by strong winds or construction. Many of us have already been infected by this organism, especially long-time residents of the Southwest or people who work here under conditions of blowing dust or disturbed soil. In parts of Arizona, more than 60% of people will have a positive skin test showing previous infection by this organism. Coccidioides, or “cocci” as it is abbreviated in the medical community, causes an infection called coccidiomycosis in humans and many other mammals (notably dogs).



I myself have a lung nodule approaching an inch in diameter that almost certainly is a coccidiomycosis granuloma from a long-ago infection. Luckily, like most people, I was completely oblivious to the infection and probably considered it merely a chest cold, if I had any symptoms at all. The nodule has been stable for fifteen years at least, and is very unlikely to cause me any harm.

However, the infection has been known to reactivate years later if the immune system is weakened. And for those who are already immunologically compromised, for example people on steroid treatment or fighting an HIV infection, the disease can run rampant in almost every organ system in the body.  It’s of particular concern when it gets established in the bones or in the structures of the central nervous system such as the meninges (the membranes that line the brain and spinal cord.) Because of its many manifestations, and lack of uniquely characteristic symptoms, it has often been misdiagnosed as ordinary pneumonia, lung cancer, or other unrelated diseases. These days, however, we have pretty good blood tests available to show its presence, and certainly physicians who practice in our area are well aware of it. Approximately 1 in 1000 people are diagnosed with the disease in a given year in Arizona, but undoubtedly there are far more people infected who are never definitively diagnosed with it. It can be treated with anti-fungal medications such as fluconazole, but there is no guarantee that these will be effective.



The organism exists in arid soils from south Texas to the interior valleys of California, and down into Mexico and desert portions of Central and South America. It lives between 40 degrees North and 40 degrees South latitude, and has been found in soils as high as 10,000 feet above sea level.

There’s very little you can do to avoid infection. Respirators are typically not fine enough to keep out the spores. Avoiding blowing dust is the primary means of prevention, and early recognition and treatment of the disease is helpful. If you’re suffering a puzzling chronic illness, you and your doctor may want to think about getting a “cocci titer” test. Depending on what organ systems are involved, disseminated cases will sometimes require such invasive procedures as a bone biopsy or spinal tap.

On that happy note, let’s return to our favorite topic of delicious edible mushrooms. I just got sent some gorgeous pictures of Boletus barrowsii and B. edulis from up around the Big Lake area.  New posting to follow…


About Christopher May

Chris is a radiologist in private practice in Scottsdale. He is married to Barbara May, with two grown children, Megan and Nick.
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