Fungal infections become more common as their range of distribution increases

Fungal infections are more common than doctors or patients realize, research suggests. And they are expected to grow even more in the coming years.

“We’re definitely seeing disease in locations that we didn’t have before,” says Dr. George Thompson, an infectious disease specialist at the University of California, Davis. “And that’s concerning because if we recognize those locations, where are the places that haven’t been fully recognized yet?”

Thompson co-authored an article published Monday in the journal Annals of Internal Medicine suggesting that more than 10% of fungal infections are diagnosed outside regions where the pathogens are known to be endemic. In addition, the paper says, misdiagnoses and a lack of data make it difficult to know how common cases really are.

That becomes an increasingly pressing problem as research shows that climate change is making these infections more diffuse. For example, coccidioides, the fungus that causes valley fever, thrives in desert climates, so increased heat and drought have created more hospitable areas to grow.

View of the desert, Sedona, Arizona, 2009.
Sedona, Arizona, 2009. Carol M. Highsmith/Getty Images file

Meanwhile, the fungus histoplasma, which can cause an illness characterized by fever, cough and fatigue, tends to survive longer in high humidity – a condition that is also becoming more common as temperatures rise. In addition, histoplasm is found in soil containing large amounts of bird and bat droppings, and climate change is changing the migration patterns of some of those species.

People generally get fungal infections after inhaling spores. Often the immune system fights off these invaders, or infections result in mild flu-like symptoms that go away on their own. But some people – usually those with weakened immune systems – can develop life-threatening illnesses, such as pneumonia or meningitis.

“The vast majority of people who get valley fever will tell you they have a cough that lasts for a few weeks and goes away,” says Dr. Arturo Casadevall, a microbiologist and immunologist at Johns Hopkins University School of Medicine. “But when people are immunosuppressed or when they’re just unlucky because they got a very high dose, these diseases can spread or go beyond the lungs.”

Typically, different fungal infections are associated with specific regions: Valley fever, for example, is most common in the Southwest, while histoplasmosis is most commonly diagnosed in central and eastern states. But the coccidioides fungus was found in Washington soil in 2014.

Thompson’s paper came just weeks after another study revealed high rates of fungal disease diagnoses far beyond their traditionally understood geographies. The researchers found that 94% of US states had at least one county with a significant number of histoplasmosis cases, and 69% had at least one county with a significant number of valley fever cases.

“In recent years, I’ve had a lot of requests to help with these illnesses,” said Andrej Spec, a co-author of that paper and an infectious disease specialist at Washington University School of Medicine in St. Louis. . “Often I would get a request that started with, ‘Interestingly, we don’t have this disease in Massachusetts. But here’s a patient who’s never traveled from Massachusetts and he’s got it, so funny.” But I’m like, ‘You got it; it’s just that the maps aren’t up to date anymore.’”

The last study to update the geographic distribution of disease-causing fungi in the US based on patient data was in 1969, according to the study by Spec.

On a global scale, a 2019 analysis found that fungal infections were on the rise and suggested that fungi are often overlooked as sources of infection. A World Health Organization report in October also found that serious yeast infections were more common in people with pre-existing health conditions during the Covid pandemic.

Climate change isn’t the only likely factor fueling this trend, Casadevall said. More travel to places where fungal infections are more common may play a role, and doctors may be getting better at diagnosing infections in places where they hadn’t been detected before.

But Casadevall said many U.S. hospitals don’t report fungal infections to the CDC, and that the agency has historically not prioritized collecting this data because fungi generally don’t cause outbreaks. The CDC received more than 20,000 reports of valley fever and approximately 1,100 reports of confirmed or probable histoplasmosis in 2019.

Thompson and other infectious disease experts are calling for national surveillance of fungal infections and urging doctors to test for them more often.

Fungal infections are not easily picked up on routine tests, so if doctors don’t know this could be a risk, they may not order the right tests. The later a diagnosis is made, the longer it takes to treat a patient, which can lead to higher medical costs and a greater chance of serious illness or death. In some cases, fungal infections can take months of treatment to clear up and can become chronic.

Dr. David Denning, chief executive of Global Action for Fungal Infections, an advocacy and research group, said some rapid tests allow doctors to diagnose fungal infections in hours or minutes, but they are not widely available in the U.S. (the standard way to test is to send a urine or blood sample to a lab and then wait several days for the result.)

“There are very few molecular tests for fungi that have been approved by the FDA,” Denning said. “The FDA rules are pretty strict, which is a good thing, but it’s also a bad thing because all of Europe is using these tests and in the US there’s too much of a barrier to getting these tests done routinely.”

A lot of people aren’t diagnosed at all, Thompson said: “There’s probably a significant number of patients who have never been directly diagnosed and who really have a lot more morbidity from their disease.”

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