Fungi are having a moment, fueled by popular culture like The Last of Us. While a fungal apocalypse isn’t imminent, fungal infections are a growing health concern, proving more difficult to treat than bacterial infections. Let’s explore why.
Why Fungi Rarely Infect Us
Most fungi thrive in moderate temperatures around 70-80°F (21-27°C), significantly lower than our internal body temperature of 98.6°F (37°C). Although we carry some fungi internally, their numbers are far fewer than bacteria, and harmful infections are rare. Dr. Arturo Casadevall, a Johns Hopkins molecular microbiologist specializing in fungal infections, explains that our body temperature acts as a natural defense.
The Rise of Fungal Infections
The HIV/AIDS epidemic brought fungal infections to the forefront. Weakened immune systems, a hallmark of HIV/AIDS before antiretroviral therapy, led to unprecedented fungal outbreaks. Thankfully, these infections are now less common with effective HIV treatment. However, other factors are making humans more susceptible.
Advances in medicine, such as organ transplants and cancer treatments, often involve immunosuppressant drugs. This temporary immune suppression creates an opportunity for fungi to invade. Treating fungal infections in these patients becomes doubly challenging because the weakened immune system can’t effectively assist antifungal medications.
Dr. Casadevall explains, “Bacteria can cause disease in small numbers. Fungi, however, multiply slowly, often reaching large numbers before treatment begins. This, coupled with less effective antifungals compared to antibiotics, makes treatment difficult. Furthermore, antifungals rely on a cooperative immune response, which is often compromised in these patients.”
Limited Treatment Options and Growing Resistance
Another hurdle is the limited number of antifungal drugs. Only four major classes of antifungals exist, with just 10 FDA-approved drugs for systemic infections. In contrast, bacteria have eight major classes and hundreds of available antibiotics. This scarcity is partly due to our biological similarity to fungi.
Dr. Mahmoud Ghannoum, a dermatology professor at Case Western Reserve University, points out, “Fungi are eukaryotes, like us, while bacteria are prokaryotes. Finding drugs that harm fungi without significant toxicity to humans is challenging.”
Adding to the complexity, fungi, like bacteria, are developing drug resistance. Cases of drug-resistant ringworm, including sexually transmitted strains, are increasing. Climate change is also a factor, contributing to heat-tolerant fungi. Candida auris, discovered in 2009, exemplifies this threat, often resisting multiple antifungals and spreading rapidly in healthcare settings.
Candida auris and Climate Change
Evidence suggests C. auris may be the first fungal infection linked to climate change, potentially paving the way for others. Climate change can also expand the range of certain fungi, as seen with Valley fever, traditionally confined to the Southwestern U.S. but now appearing elsewhere.
Dr. Casadevall, co-author of What If Fungi Win?, which explores the growing fungal threat to human health and ecosystems, emphasizes, “Everything adapts or dies. As fungi adapt, our body temperature defense becomes less effective.”
Hope for the Future
Despite the challenges, progress is being made. New antifungals and vaccines are under development, along with refined immunosuppressant therapies to minimize opportunistic infections. Research is also focused on reducing or eliminating immunosuppressants in organ transplants and boosting immunity to combat fungal infections directly.
While the threat of fungal infections is real and growing, humanity is actively working to adapt and develop effective countermeasures.
