Valley Fever

Out of the millions of fungal species in the world, only a few hundred have the potential to cause illness in humans. One such fungus is Coccidioides, known for its ability to cause serious infections. What makes this fungus particularly intriguing is its unique adaptation to thrive in desert environments. While most fungi prefer dark, damp, and cool conditions, Coccidioides has discovered a way to survive in arid regions. But that's not the only fascinating aspect of this fungus—there's still so much we don't know about it.

Coccidioides has existed for centuries, yet many mysteries surround its behaviour. Its exact location at any given time and how it spreads in the soil remain elusive. We can only speculate about the reasons behind its expansion. The infection caused by Coccidioides goes by various names, such as Coccidioidomycosis, Desert Rheumatism, San Joaquin Valley Fever, or simply Valley Fever. The symptoms are flu-like, including fatigue, fever, and body aches, which can persist for over a month.

In some cases, individuals may develop fungal pneumonia, while others may experience more severe conditions like chronic lung disease, skin abscesses, or even meningitis, which can be fatal. Fortunately, only about four in ten people develop symptoms, and outbreaks are relatively rare. Currently, 97% of reported Valley Fever cases in the US occur in Arizona or California, although some states do not report the disease nationally, making Texas a potential hotspot.

Officially, 20,000 cases of Valley Fever were reported to the CDC in 2019. However, researchers believe the actual number could be closer to 350,000 annually, accounting for underreporting and misdiagnoses. The reported cases have been steadily increasing year after year, with California reporting a staggering 159% increase from 2013 to 2019. Additionally, the fungus is being discovered in new locations. While it is typically found in the soil of the southwestern US, parts of Mexico, and Central and South America, researchers identified it in Washington State in 2014. It's highly likely that the fungus is already present in the soil of states beyond its known range, adding to the intrigue of its movement and expansion.

Understanding the spread of this mysterious fungus is complex and requires unravelling multiple factors. First, let's explore the unique characteristics of Coccidioides itself. The fungus exists in two forms: an environmental form that resides in the desert soil and a parasitic form that multiplies in the human body. When the soil is disturbed, such as during dust storms or construction, Coccidioides releases spores into the air. Inhalation of these spores can lead to infection in mammals, including humans.

Interestingly, Coccidioides doesn't necessarily rely on dead animals to begin its digestion process. Instead, it can start consuming the host from the inside out while the animal is still alive. Despite its long existence, there are still many unknowns about the behaviour and movement of this fungus. To understand its spread, scientists speculate that three interrelated factors play a role.

The first factor is the behaviour of desert rodents and the Endozoan Hypothesis. Desert rodents, like kangaroo rats, can inhale Coccidioides spores while digging their burrows. The fungus may lay dormant in their lungs or cause their death. In either case, Coccidioides becomes the first organism to feed on the deceased rodent. This feeding process plays a crucial role in its survival and dispersal. When the rodent's remains decompose, the fungus is released back into the soil, waiting to be inhaled by another host. This dynamic indicates that a higher population of desert rodents could facilitate the movement of the fungus through the soil.

The second contributing factor is extreme weather conditions. Periods of heavy rain result in increased vegetation, creating a surplus of food for desert rodents. This abundance leads to a higher population of rodents, thus increasing the chances of the fungus being inhaled. However, as the desert climate reverts to a dry state, drought conditions reduce the rodent population, causing the release of Coccidioides back into the soil.

These factors combined create an intricate cycle of fungus-host interactions that perpetuates its spread. However, due to limited knowledge about Coccidioides, confirming the Endozoan Hypothesis and understanding the fungus's movement remains challenging. Detecting Coccidioides in soil samples has proven difficult, and current tests may not always detect its presence accurately.

The expanding range of Coccidioides is a cause for concern, especially considering the rising temperatures in the US. Climate change could potentially extend the fungus's reach, leading to an increased risk of infection. One study suggests that by 2095, the range of Coccidioides could more than double due to arid conditions intensifying across the country. Moreover, factors such as construction activities in the desert and population booms in cities like Phoenix contribute to the growing number of Valley Fever cases.

While researchers focus on prevention and have made progress in developing a vaccine, there is still much to learn about this enigmatic fungus. Coccidioides serves as a reminder of how our world is constantly changing, sometimes in small, mysterious ways that challenge scientific understanding. Although this particular fungus may seem alarming, it's essential to maintain perspective and not hyper-focus on one specific infection. Instead, let it serve as a testament to the intricate complexity of nature and the ongoing quest for knowledge.