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Nothing you learn is wasted

Yale Medicine Magazine, 2022 Issue 168 More than skin deep
by Yeager, Ben


YSM alumnus Brendan Jackson works at the CDC monitoring fungal diseases. His time at YSM prepared him well to track down causes of outbreaks, especially when they have no obvious explanation.

Brendan R. Jackson, MD, MPH, considers himself a generalist. A curious nature and passion for investigation attracted him to internal medicine, then to the Centers for Disease Control and Prevention’s Epidemic Intelligence Service, or EIS, where he specialized in foodborne and waterborne diseases. Now his research is focused on a poorly understood and growing threat to public health: fungal infections.

In explaining what EIS does, Jackson related a parable: A man waits at the bottom of a cliff from which people keep falling. Paramedics try to save the fallen. Finally, somebody says they’re going to climb to the top and put up a fence in front of the cliff. “The whole idea of an ounce of prevention leading to a pound of cure was very appealing to me,” Jackson said, “especially within our medical system, which often feels like way too much too late.”

Jackson remembers watching the movie Outbreak when it came out in 1995 and thinking the profession looked exciting—hazmat suits and airplanes flying into exotic locales. The reality is more mundane, but Jackson still finds his job fascinating and engaging. Stationed at the CDC headquarters in Atlanta, Jackson leads a team of 15 people working with state health departments, performing data analysis and surveillance in an effort to prevent and stem outbreaks.

Looking at the bigger picture

Jackson’s early cases show the necessity of holistic investigations as well as sudden breakthroughs. It comes down to finding a small connection within a broad environment. There was an outbreak in Georgia of a brain-eating amoeba that lived in soil and infected a landscaper who died and infected others after his organs were harvested. There was an outbreak on the U.S./Mexico border that prompted Jackson to learn about the area’s complex water systems. There was a Listeria outbreak in 2014 that came down to caramel apples from a packing facility in California.

“I’m interested in a lot of different things, and public health lets you take problems beyond the clinic and look at how everything ties in, human behavior, sociology, and everything else,” Jackson said.

Inevitably the question arises: Why fungi? “Mostly for the puns,” Jackson said. “When I tell people I work in fungal diseases, I know a lot of people start thinking about their toes.”

In truth, a large number of fungal diseases can cause severe illness and death, and research in the field is a growth industry. Part of the increase in these diseases is due to the fact that humans are living longer with certain conditions and immunosuppressive regimens. Climate change and other environmental disruptions are also important factors. Fungi are changing right along with their human environment. They constitute an entire kingdom of 2.2 to 3.8 million species, most of which have never been described; all are researched by only a small branch of the CDC, and treated with only three main types of antifungal drugs for severe disease.

The threat of fungal infections

Jackson recounted a researcher’s hypothesis that warming temperatures are increasingly causing fungi to invade the human body, as higher mammalian body temperatures typically keep such infections away, but now the gap between human body temperatures and the ambient one is narrowing. This convergence could cause fungus to become one of humanity’s main pathogens, as it is with plants, reptiles, and amphibians.

Of these super-fungi, Jackson is most concerned about Candida auris, a fungus discovered in the ear canal of an elderly woman in Japan. First described in 2009, C. auris was thought to be benign until it was found to cause invasive bloodstream infections. It showed up in South Asia, and then suddenly South Africa, then Venezuela, then a hospital in the United Kingdom, and is now increasingly spreading across the United States. “There are millions of species in the environment that we know nothing about,” Jackson said. “My suspicion is that Candida auris is probably one of them, and we intruded into it somehow, whether through aquaculture or agriculture, deforestation or whatever else.”

Fungi are complex eukaryotic organisms. Unlike viruses and bacteria, many reproduce sexually, allowing them to adapt rapidly. They are opportunistic creatures that look for any opening. The COVID-19 pandemic has been one example; Jackson’s team has tracked an increasing number of fungal infections in patients hospitalized with COVID-19, especially in those receiving steroids and other immunosuppressive medications. “With almost any infectious disease, you change one part of the system, and it’s going to change so many other interlinked parts,” Jackson said. “Whether that’s a disturbance to the human body, or whether that’s a disturbance in our broader culture or systems, there are ripple effects.”

Jackson’s father was a CDC EIS officer in the ‘70s and told him that nothing you ever learn is wasted. Jackson had his doubts through college and medical school, but now his father’s schema lies at the core of his professional life: You can use seemingly disparate bits of knowledge to solve a public health problem, whether medicine and epidemiology or the geology and hydrology he learned on a cross-country college trip, or agriculture and the food industry.

“It’s the synthetic nature of it all together,” Jackson said. “And when crossing silos, there’s always lots more to learn.”