What are Fungal Storms?

If you judge by its name, you might look for a fungal storm in a humid climate, because fungi thrive in damp, moist conditions, right?  Yes, your reasoning is correct!.  But we’re talking about fungi living in, and becoming stirred up from, a most unusual place for moisture-loving organisms: the arid earth of the southwest US. 

Last year we posted an article on “Valley Fever”.  This disease is named for the San Joaquin Valley in California, where the first US case was diagnosed (Kern County). (Valley Fever, It’s in the Air, Be Aware)   The technical name for Valley Fever is Coccidioidomycosis, and if you don’t live outside of the southwest US, you might have never heard of this disease–until now.  That’s because Valley Fever is just one of several diseases that are spreading in geographic area, because of weather patterns. 

The San Joaquin Valley is in central California, and California and points south and east of it are known for their dry heat (hello–it’s wildfire central!)  This climate and soil, oddly enough, are where the fungus that causes Valley Fever, thrives. 

This southwest soil and climate are also ideal for several other fungal diseases to thrive. Following are the most common species of disease-causing fungi; the first two (Coccidiodes and Aspergillus) tend to be the most dangerous to humans.  Coccidioides can cause severe pulmonary disease and chronic infections in some cases, while Aspergillus species, especially drug-resistant strains, can lead to life-threatening infections in people with weakened immune systems.  (Are fungal storms becoming more common? What they are, when they strike)

• Coccidioides species – Responsible for Valley Fever, found mainly in the dry soils of the U.S. Southwest. Spores become airborne when soil is disturbed by dust storms, construction, or earthquakes.

• Aspergillus species – Includes A. fumigatus and A. flavus, which thrive in warm, humid soils and decaying vegetation. Airborne spores can travel long distances and infect lungs, especially in immunocompromised individuals.

• Histoplasma capsulatum – Common in soils enriched with bird or bat droppings. Disturbances such as construction or flooding can send spores into the air.

• Blastomyces dermatitidis – Found in moist soils and near water bodies; spores can spread when soil is churned by storms, floods, or human activity.  

As we explained in the first article, scientists have been studying why Valley Fever seems to be more prevalent in some years and not others, and it has to do with seasonal patterns of precipitation.  They have formulated a “grow and blow” hypothesis.  Specifically, a dry foresummer or fall kills other microorganisms that might compete with Coccidioides. Subsequently, winter rainfall leads to spore formation in the soil, which are released whenever the soil dries out again.   (https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016GH000033)  The fungus is most prevalent in the top 2-12 inches of soil, so when hot weather dries it out, any type of disturbance can send spores flying.  This could be a “haboob” (an intense dust or sand storm, watch this video to learn more about them), a regular dust storm, construction or farming activity, or even an earthquake.  

Here’s the sneaky part: in their dry form, these fungi are not giving off their characteristic musty “mold” odor (microbial VOCs).  Therefore during windy conditions or a dust storm or just gardening, people are not aware that they could be breathing in dangerous mold spores.  Check out the map below; the dark orange area is the areas scientists already know that coccidioides already lives, but there is a light shaded orange area where, due to changes in weather and climate, the fungus may spread.  The reality is that these are very dangerous diseases and during a dust storm or dry weather with any outdoor activity, it’s important to take precautions.

Source: Areas with Valley Fever

Most of these precautions involve avoidance of the dust by wetting soil down, suspending activity during high winds or dust storms, and remaining upwind or in air conditioned vehicles using HEPA air filters, but when this is not possible, workers need to wear approved respirators, not just loose-fitting “dust” masks.  In addition, workers need to clean themselves, their clothing and equipment after working in order to prevent transportation of the fungus to other areas.  For specific actions to reduce contracting the disease, this fact sheet is really helpful. 

As for Aspergillus, the other most dangerous species on the list above, scientists are also predicting a larger “footprint” because increasing humidity and extreme weather events can allow it to flourish in new areas, and its genome bends easily to new pressures..   Aspergillus grows really well in moist soil, decaying leaves, and food crops, and the standard pesticides used against it on food crops could actually foster drug-resistance in hospitals.  The fungicide treatment against mold propagation in wheat and peanuts and the treatment for patients that have a fungal infection are the same class of drugs: azoles.  This is not good, because spores that survive the fungicide can adapt to become resistant to the medication: “Each hectare treated with agricultural azoles raises the odds that environmental spores will carry resistance genes into hospitals.” (Deadly fungus that "eats you from the inside out" is quickly spreading around the world as temperatures warm)

Fungal infection outbreaks are rare and usually affect those who are already immuno-compromised or struggling in intensive care units, such as those recovering from influenza or COVID-19.  However, many people already know someone like this in their families or social circle, and these diseases have been known to infect healthy people, such as the two men in this video (testimonies starting at 49 seconds).  Most disturbingly, in Chris Sams, the infection has moved to his spine and brain.  He says, “It’s more than just a dust storm because it’s going to get into your lungs, and then it will affect how your life is for the rest of it”.  We hope that even just reading this article will help you realize the risk!

Photo by Matthieu Joannon on Unsplash