September 23rd-27th is “Fungal Disease Awareness Week” “Seems like everything is getting a week, these days” one may say to themselves, “Fungal diseases only happen to people who have weakened immune systems”. This just isn’t true!
Fungal allergies are perhaps the most widely known fungal related illness- resulting in typical allergy symptoms including coughing, sneezing, shortness of breath, itchy eyes, runny nose, etc. However, in addition to allergies, other types of fungal diseases exist. There are the controversial illnesses of mycotoxicosis and CIRS or Chronic Inflammatory Response Syndrome, and of course the historically “rare” fungal infections. It should be noted that fungal infections in the immunocompetent - people who have healthy functioning immune systems - are on the rise. It’s not just the immunocompromised folks who are at risk anymore. As a result, we are seeing an increase in fungal infections and fungal related illnesses across the board. Of course, there are many suspected causes for this increase in incidence. Issues with building standards, changing weather patterns, and the increased use of antifungals in agriculture may be partly to blame.
Building standards took a turn during the oil crisis in the 70’s, we began building structures tighter as to save on heating and cooling costs. In doing so, we managed to decrease ventilation- or how a building breathes. The result: trapping of noxious fumes and moisture within the building interior. Trapped moisture and stagnant air create the perfect breeding ground for fungi aka mold. To compound the issue, our building materials of today are far different from those of the past. The widespread use of drywall starting between 1940-1960 meant easier interior construction, but there were unforeseen issues hiding in plain sight of the modern-day convenience. A study published in 2016 demonstrated that when drywall is placed in a sterile petri dish, and sterile water is added- some of the more dangerous molds grow from this sterile process. The take home is that the drywall we line our homes with comes pre-inoculated with dangerous mold spores1- literally all you have to do is “just add water”. As some builders have become aware of mold issues, there has been a movement towards using greenboard, which is a drywall that has its exterior paper treated with antifungal chemicals. The issue here is twofold: when the antifungal chemicals have dissipated you are still left with a surface that contains paper- one of mold’s favorite foods. The other concern is that the antifungal chemicals used on the greenboard may be adding to the problem of antifungal resistance. There has been a general trend toward an increase in antifungal resistance of common indoor molds, including the indoor molds that can affect human health like Aspergillus fumigatus and Aspergillus niger. Could the anti-fungal treated greenboard we now use be adding to the antifungal resistance we are seeing in the greater medical community? Or could it be something else- like the widespread use of antifungals in agriculture? Or perhaps a combination?
The use of antifungals in the agricultural sector is immense, in fact “thousands of tons” of azoles, a class of antifungals, are applied to crops each year2. Antifungal use in agriculture is not new, although it seems like the discussion of antibiotic use in livestock has been stealing the limelight for quite some time. Although the antifungal chemicals we use in the agricultural sector are not the EXACT same versions as their medical counterparts, they are still the same class of compounds. This means that they are structurally similar and have the same mechanism of action when it comes to killing fungi. As a result of widespread agricultural use, we see cross over resistance in the medical community. For example- it is possible for the fungi that infects plants to become resistant to these antifungal chemicals. Consider for a moment a farmer who is exposed to his field daily, it is wholly possible for him to inhale and thus develop an infection of said resistant fungi- and unfortunately those azole resistant agricultural fungi may also be resistant to the same class of azole medical drugs that would otherwise save his life! This isn’t just theory, there is research demonstrating dangerous molds like Aspergillus fumigatus can become resistant to azoles as a result of environmental exposure! In fact, there have been case studies of people who have been diagnosed with invasive Aspergillus fumigatus who test positive for azole resistance- who have never touched the drug before3.
Our changing weather patterns should not go unmentioned. Hurricane seasons have grown more dangerous over the years and we now find ourselves having to deal with serious storms leading to record flooding. Where there’s flooding - there’s water damage, and where there’s water damage-there’s mold. Even something as simple as an increase in relative humidity in a normally dry climate can wreak havoc on building material that is ill equipped for a damp environment.
You may ask “So what does all this have to do with fungal awareness week?”. The major issue at hand is that mold related illnesses are on the rise and included therein are fungal infections like invasive pulmonary aspergillosis, which is a lung infection caused by the Aspergillus family of molds. But, to further complicate this matter, we are also seeing an increase in RARE fungal infections, potentially as a result of the increased antifungal resistance and exposure to moldy indoor environments. For instance, the medical literature has documented fungal infections caused by Chaetomium globosum4, 5, Aureobasidium pullulans6,7,8 and Wallemia sebi9 - all of which are unusual pathogens in humans- but are common in water damaged buildings!
So, yes, as the CDC says- be sure to “Think Fungus”10- when faced with infections that are non-responsive to antibiotics. However, I suggest we take it one step further- as we should consider rare fungi in those cases- including indoor molds.