Fungal infections have been on the rise since COVID-19's inception, but public health tracking tools, tests, and data systems in the U.S. are not quite where they need to be yet, Tom Chiller, MD, CDC's head of mycotic diseases, told Becker's.
"We don't have good surveillance for fungal infections," Dr. Chiller said. "A lot of our information is piecemeal or is institutional. We don't have a national fungal surveillance system. So it's often hard to say with definitive facts and data that things are increasing or decreasing, staying the same."
While there may not yet be robust systems in place to determine all of the important public health indicators related to fungal infections, there are some tools that exist and which are being used to track specific emerging fungal infections — like Candida auris — which the CDC began tracking in 2018. This, along with other indicators including environmental factors like climate change, are signaling that the emergence of new, severe fungal-caused infections is expected to continue, he explained.
Expect the unexpected
As the planet warms, fungi may be able to emerge and thrive in environments they previously have not been able to. And with these conditions, fungal infections that are increasingly drug-resistant are also likely, Dr. Chiller explained.
Fungal infections are opportunistic, since they are closely linked to the environment, some spores can be in the air in almost any place. Our immune systems are the defense we have currently when breathing anything in that could be a pathogen, but as other factors continue to promote the emergence of drug-resistant fungi, that could be concerning for public health officials, he said.
"There are certainly indications that there may be more of them and new ones coming as well, that may be more resistant, more thermo-tolerant, more able to survive in general," Dr. Chiller said. "We know that environmental changes are going to affect fungi and I think they could affect them. They could cause certain fungi to outcompete others that weren't as thriving as well in a lower temperature but now are thriving better at a higher temperature. Those then fungi could outcompete those others. And it could be that those fungi then might be more pathogenic to humans or animals, or even plants."
Since many crops are sprayed with protective pathogens that are fungi, this could lead to more risk.
"Probably 80 percent of crop pathogens are fungi. That also creates a higher risk for us because one of our defenses that we probably developed over millions of years is the ability to have a high internal body temperature and most fungi grow at a much lower temperature than our body," Dr. Chiller said. "As temperatures increase in the environment and as they adapt to these higher temperatures, they will become closer and closer to being able to survive our temperatures and to then survive within humans. That's going to be challenging because that's going to potentially create more successful fungal pathogens."
Dr. Chiller said there are between 3 million and 5 million species of fungi, but only about 120,000 that are actually identified. Only a fraction of them cause human diseases, but that number is rising.
"The potential is unfortunately huge for there to be more pathogens because [right now] we're only aware of a sliver of the fungal species out there," he said. "So it certainly makes me concerned knowing that fungi are hardy, adaptable, they are the most similar organism to humans to human cells, which makes them hard to kill and hard to identify because they're similar to our own bodies and therefore drugs that kill fungi kill human cells, potentially. So we will have to find specific targets for new antifungal drugs."
Where physicians come in
While there may not be the tools to-date to track or diagnostically test all known — or unknown and emerging — fungal pathogens yet, Dr. Chiller said further education about fungal infections in medical schools, within hospital environments and encouraging physicians to "Think fungus" when considering diagnoses can help in the meantime.
"Right now if you don't have a test you don't know that you're dealing with this sort of as a clinical syndrome. The fungal clinical illnesses look like every other illness and so it can be really hard to distinguish them…" he said. "They'll have to consider if a diagnosis could be a fungal infection. What we can do today is start thinking about fungus more when it comes to our patients and make the diagnosis if we think it's a possibility."
The CDC's mycotic diseases division is also working toward improvements in testing and tracking to strengthen systems that are in place for public health officials as these infections continue to become more common.
"This is a kingdom of organisms that is going to be challenging to deal with," Dr. Chiller said. "It's here to stay."