Ancient Mushroom, Modern Medicine: Paul Stamets Says Agarikon Mycelium May Be Key to Fighting Viral Pandemics

By Allison Proffitt

March 12, 2026 | Paul Stamets has spent more than four decades in the forests of the Pacific Northwest, carefully prying tissue samples from the undersides of some of the world’s rarest mushrooms. On the stage of February’s Integrative Health Symposium, that lifetime of fieldwork converged with randomized clinical trials and Department of Defense contracts—a collision of ancient ethnobotany and 21st-century immunology that left the audience energized. 

The World’s Longest-Lived Mushroom 

At the center of Stamets’ presentation was Agarikon (Fomitopsis officinalis), a conk mushroom that grows on old-growth conifers in the Pacific Northwest and has been used medicinally for millennia in European and indigenous cultures. He describes it as the longest-lived mushroom in the world, with individual specimens surviving 150 years or more. It is also, he noted soberly, on the edge of extinction — legally protected, harvestable only in small quantities from mature trees. 

Beginning in the early 1980s, Stamets made it a personal mission to collect Agarikon strains before they disappeared. He now holds a genomic library of 118 distinct strains—a collection he described as “a national treasure.” The strains are being genomically sequenced and uploaded to a public database. “If there’s a fire coming,” he said, “this is the one thing I’m going to save.” 

His entry into antiviral research came through a chance encounter in 1979 with Dr. Frank Piraino, a medical virologist at the University of Wisconsin-Madison Medical School, who asked Stamets for mushroom samples. Two decades later, in 1999, Piraino published research on a novel antiviral compound—RC183—derived from those samples. The work caught Stamets’ attention and shaped the trajectory of his research for years to come. 

From Bioterrorism Funding to COVID Clinical Trials 

The post-9-11 era proved to be an unlikely turning point. When bioterrorism rose to the top of U.S. government concerns, Stamets submitted extracts from Agarikon, chaga, turkey tail, oyster mushrooms, and other mushrooms to BioShield, a government-funded antiviral screening program backed by the Department of Defense and the National Institute of Allergy and Infectious Diseases. The program ran 2,392 assays on the samples. 

Of the seven Agarikon strains he submitted, three showed what Stamets described as “remarkable” antiviral activity against smallpox-related poxviruses, herpes viruses, and influenza strains including H1N1, H3N2, and H5N1. Russian virologists, he said, also documented antiviral properties through independent work (DOI:10.17265/2328-2150/2015.08.001). In in vitro tests conducted more recently, Agarikon extracts showed the ability to reduce plaque formation in cells infected with SARS-CoV-2, the virus responsible for COVID-19. 

Despite those results, moving the research into clinical settings required funding. The breakthrough came when he and his collaborators at the University of California, San Diego, led by principal investigator Gordon Saxe, designed two placebo-controlled, randomized clinical trials. 

Two Clinical Trials, Two Surprising Findings 

The first trial enrolled 90 patients receiving mRNA COVID-19 vaccines. Participants were recruited, Stamets said, directly from hospital vaccination lines. Half received a combination of Agarikon and turkey tail mycelium (called FoTv); half received a placebo. Those in the treatment group reported significantly reduced vaccine side effects — sore throat, headache, and muscle aches — compared to the placebo group. 

More striking, according to Stamets, was what happened to their antibodies. While antibody levels typically decline after vaccination, the treatment group showed sustained — and in some cases increased — antibody titers at the six-month mark. The effect was particularly pronounced against the spike protein and its receptor-binding domain, the key targets of COVID immunity. The study was published in BMC Immunology (DOI: 10.1186/s12865-026-00809-9). 

The second trial enrolled 50 patients who had arrived at emergency rooms sick enough with COVID-19 to require hospitalization. Some were vaccinated; some were not. All received the Agarikon and turkey tail mycelium combination for 14 days. Stamets reported substantial reductions in COVID-associated symptoms across the group. The Agarikon-plus-turkey-tail group, he said, reached symptom resolution roughly 10 to 12 days faster than the control group. 

“This is the first study ever conducted as a placebo-controlled, randomized clinical study using fungi to enhance vaccination efficacy,” Stamets told the audience.  

Turkey Tail, Cytokine Storms, and the FDA 

Turkey tail (Trametes versicolor) has its own clinical pedigree. Stamets described a Phase 1 trial in breast cancer patients in which mycelium-based turkey tail extracts produced dose-dependent increases in CD8+ T-cell counts. He also mentioned his own mother, who was diagnosed with terminal breast cancer in 2011 at age 84 and, by his account, significantly outlived her prognosis while taking turkey tail mycelium. 

The COVID pandemic introduced a new complication: some physicians grew wary of recommending immune-stimulating mushrooms to COVID patients, fearing they might worsen the cytokine storms associated with severe disease. Stamets said that concern prompted him and colleagues to publish research demonstrating that mycelium — specifically the fermented substrate form, rather than just the mycelium alone — stimulated the production of anti-inflammatory interleukins while reducing the pro-inflammatory interleukins linked to cytokine storm. That data, he said, was enough to satisfy the FDA when his team sought approval to proceed with the COVID clinical trials.  

A separate randomized placebo-controlled study, he noted, found that turkey tail mycelium acted as a prebiotic in patients whose gut microbiomes had been disrupted by antibiotics, helping restore healthy bacterial populations within the microbiome (DOI: 10.4161/gmic.29558).  

The Next Pandemic: A Warning About H5N1

Stamets closed with an urgent warning about H5N1 avian influenza. He noted that the virus has done something unprecedented in medical history: it is jumping an unusually wide range of species, having been detected not only in birds but in swine, cattle, sea lions, seals, large cats, and, in Washington State, in local wildlife populations. Mortality rates in human cases, he said, have ranged from 47% to 50%. 

“We are going to face a worldwide pandemic again,” he said flatly. “Too many potential patient zeroes.” The primary symptom profile of H5N1 closely mirrors that of COVID-19, he observed—the major distinguishing feature being the absence of loss of smell—suggesting the two diseases may respond to similar immune-modulating strategies. 

He argued that broad-spectrum immune support, of the kind suggested by his Agarikon research, could prove valuable precisely because it does not target a single pathogen. “You’re not just using the immune system, you’re going to customize it,” to respond to emerging threats, he said. He also pointed to the growing strain library as a potential resource: with 118 Agarikon strains now catalogued, he hopes to identify a “super strain” with maximally potent antiviral properties, though he suggested the combination of strains already used in the trials may already be sufficient. 

Scaling the Mycelium