The dust storms that frequent the Southwest are a common exposure vector for the fungus that causes valley fever. Via marksontok/Flickr
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Micrograph of coccidioidomycosis, also known as valley fever. Image via Wikimedia
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Distribution of valley fever in the Southwest, via the CDC
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This CDC graph shows the growth in reported valley fever cases. Tens
of thousands more go unreported every year, according to the CDC.
It’s when the immune system fails to contain these spherules that the fungus can propagate throughout its victim, sometimes with deadly consequences. As an infected rodent dies, collapsing into the desert, the cocci burst out of suspended animation and unleash streamers of hyphae that eat the rotting meat. As the fungus feasts, hyphae and spores slip back into the soil, ready to start the cycle all over again. Because humans killed by the fungus are generally embalmed or cremated, they largely don't propagate the Coccidioides life cycle.“If a cocci spore gets into a human, it has made a big mistake,” Taylor said. “It might kill us but it’s not going to reproduce inside us—because they’re going to burn you or embalm you. It won’t get a chance to reproduce. It’s unlikely to ever become adapted to living in humans.”The reasons for the rise in valley fever cases are not entirely clear. Climate change, with the flood-drought cycles it is bringing, could be helping the fungus to flourish in damp soil before launching the spores when drought arrives. The changing climate is also shifting the ranges of its natural prey, including small mammals, which release spores into the soil when they die. And as they move, they're likely to bring cocci with them.The growing rate of diagnoses does reflect a growing awareness among doctors of the disease and its symptoms. People are also increasingly moving out of cities and into dusty exurbs, migrating into regions that are rich with cocci. “There’s an influx of naïve hosts,” Taylor said. “They’re now putting homes outside the cities in more rural areas, where they’re disturbing the desert.”“There’s an influx of naïve hosts. They’re now putting homes outside the cities in more rural areas, where they’re disturbing the desert.”