Coccidioidomycosis is a fungal respiratory infection of varying degrees of severity: without symptoms, acute, chronic, severe or fatal. The disease is endemic to certain geographic areas in the Americas. It is technically considered an “emerging illness,” even though doctors have been finding it in their patients for more than a century, because cases have been sharply rising in recent years. The suggestion is that this is linked to climate change.
The habitat of the causal fungus Coccidioides immitis (Cocci) is alkaline soil of the Lower Sonoran Life Zone in North, Central and South America. US counties that are endemic to Valley fever are hot and dry: have an average annual temperature above 50 degrees F, get under 600 millimeters of rain a year and the soil rarely freezes. In a prolonged drought, the fungus in the soil tends to dry up and die. When the rains eventually come back, the fungus flourishes and generates spores. Disturbing soil, especially soil that hasn’t been touched in a long time, in areas that are endemic to Cocci tends to send the fungal spores swirling into the air and, inevitably, peoples' lungs. That is why wildland firefighters tend to get Valley fever, not necessarily from the flames themselves, but from digging line breaks in the soil to help contain fires. Construction sites are responsible for a huge quantity of Valley fever infections for the same reason.
Approximately 60% of patients with primary infections are asymptomatic, 30% have mild to acute pulmonary disease.that requires medical care, and 10% have severe infections — the disseminated form of the disease, when the fungus spreads beyond the lungs into other parts of the body. Those cases can be fatal, especially among the immunosuppressed. About 25% of the patients with disseminated disease have meningitis.
The US Centers for Disease Control and Prevention (CDC) estimates that some 150,000 cases of Valley fever go undiagnosed every year.
During the early 1990s, the incidence of coccidioidomycosis in California increased dramatically, in some places, astronomically so. According to CDC data, reported Valley Fever cases in the USA increased by 32 percent between 2016 and 2018. One study determined that cases in California rose 800 percent between 2000 and 2018. Even though most infections are subclinical or self-limited, the outbreak is estimated to have cost more than $66 million in direct medical expenses and time lost from work in Kern County, California, alone. A prospective analysis that factored in climate change based on future warming scenarios found that, by the end of the 22nd century, the average total annual cost of Valley fever infections could rise to $18.5 billion per year, up from $3.9 billion in 2020..