The U.S. Centers for Disease Control has been closely tracking the new variant of avian flu emerging in the bird markets of China. But the CDC has more than that on its plate of course. One of the other emergent problems it is concerned with is a homegrown epidemic of “Valley Fever.”
“Valley Fever,” which can be a life threatening disease, is also known as coccidioidomycosis, so named after the fungus that causes the infection. In late March, the lead story in CDC’s Morbidity and Mortality Weekly Report (MMWR) was headlined “Increase in Reported Coccidioidomycosis – United States, 1998-2011” (http://www.ncbi.nlm.nih.gov/pubmed/23535687). In fact, the “increase” of the title was far from titular – an eight-fold rise in new cases in just over a decade.
Most of the cases of this still fairly uncommon disease occur in Arizona and California where soil conditions favor the fungus. The CDC speculated on certain factors that might have contributed to the recent increase in disease, ranging from evolving laboratory techniques improving diagnosis to changing environmental conditions favoring growth of the fungus (factors such as drought, rainfall, and temperature are acknowledged, but the MMWR editors are punctilious in avoiding the deadly duo “global warming” – they are already living with sequester and may have reasons to be circumspect).
A part of the story that the big picture does not illustrate is the many small outbreaks of Valley Fever that occur when an unwitting group at risk of coccidioidomycosis infection strays into a high exposure environment. A classic scenario is that of military assignment in a high “cocci” spore count area, which can include simply being on base so situated or, in a particularly high-exposure activity, carrying out desert maneuvers (for example, an outbreak documented in a group of Navy seals following a desert training exercise). Underscoring this, over the same time period covered by the CDC report, nearly 500 active duty military service members were diagnosed with Valley Fever (http://www.afhsc.mil/viewMSMR?file=2012/v19_n12.pdf#Page=2). Certain groups of civilians can be at increased risk too, especially construction workers. One of the best documented such outbreaks was in a group of civilian workers laying pipes on a military base: 10 out of the twelve member crew were infected, one of whom came down with widespread disease (http://www.ncbi.nlm.nih.gov/pubmed/?term=Cummings+KC%2C+McDowell+A%2C+Wheeler+C%2C). Certain avocations are also at risk. This can range from a group of archeologists excavating in cocci-laden soil to a single tourist out for solo desert-buggy ride. I have helped care for one such case, a man whose home-country private medical insurance denied his claim because coccidioidomycosis, considered exotic, did not appear on its fixed list of local medical conditions.
Just staying at home may not be solution either, depending on where you live. One famous outbreak of Valley Fever occurred following the 1994 Northridge earthquake among residents of Simi California and was attributed to clouds of dust from landslides in the dry hillsides.
The increasing frequency of this problem is likely to get worse if it is truly due in part to climate-driven extremes of rainfall and drought that can potentially spur on fungal “blooms.” Good thing we are still waiting to prove that global warming is real.