Blight: Fungi and the Coming Pandemic by Emily Monosson; W. W. Norton, 272 pp., $28.95
Consider fungi. They are their own kingdom, more closely related to animal than to plant. They grow and search for food with threadlike hyphae. They feed by excreting digestive juices onto their dinner, living or dead, to help break down nutrients before ingesting. There are more species of fungi (as many as six million) than there are known animal species (about two million, mostly insects) or plant species (about 400,000 terrestrial species). Fungi (except yeast) reproduce by putting out spores. Chemists estimate that in any given year, 50 million tons of fungal spores are blowing about in the air.
Most fungi are harmless; some are essential for our survival. We savor the fruiting bodies of portobellos and other mushrooms. Yeast gives us bread and beer. Fungi live in our gut microbiome along with bacteria, viruses, and protozoa. In soil, mycorrhizal fungi colonize plant roots and break down nutrients, good for trees. Saprobes (fungal decomposers) consume dead matter that otherwise would pile up. Penicillin comes from a fungus (a mold).
So what’s the problem? Fungal pathogens. Collectively, writes Emily Monosson in this well-researched, revelatory book, “infectious fungi … are the most devastating disease agents known on the planet.” Fungal threats, she elaborates, “are big, continuing, diverse, and potentially catastrophic.”
Take Candida auris (C. auris), a yeast that first appeared on the radar of the Centers for Disease Control and Prevention in 2016 and that is currently spreading around the world. It already has four genetically distinct populations and is evolving resistance to all three existing classes of antifungal drugs. In a New York hospital, after a patient died of it, the hospital’s president recounted the level of contamination: “Everything was positive—the walls, the bed, the doors, the curtains, the phones, the sink, the whiteboard, the poles, the pump. The mattress, the bed rails, the canister holes, the window shades, the ceiling.” To get rid of it, the hospital had to rip out floor and ceiling tiles from the patient’s room. Today, more than a thousand patients across the United States have it. At least 30 percent of them will die.
The threat of fungal pathogens is exploding. “Each year nearly a billion patients [worldwide] struggle with fungal infections,” Monosson writes. For “150 million it will be life threatening, and of those, more than 1.6 million people around the world will die.” This is practically the same number of deaths as from tuberculosis, and nearly three times as many as from malaria.
Fungal pathogens such as C. auris tend to kill people who are immunocompromised or immunosuppressed. This is no small club. It includes people with organ transplants (40,000 in the United States alone in 2021). It includes several million HIV-AIDS patients. It includes cancer patients. It includes some people who take high doses of steroids for conditions like asthma and chronic obstructive pulmonary disease. It includes people hospitalized for Covid-19. It includes people whose immune systems are not what they used to be—people who are aging.
Other pathogenic fungi infect people in perfect health. Such is the Coccidioides infection known as Valley fever. More than 20,000 cases were reported in the United States in 2019, and on average the infection kills two hundred people per year nationwide.
Why now? Fungi like it cold—and our very existence as a species likely came about because of this. Sixty-six million years ago, in the so-called Chicxulub Impact Event, an asteroid smashed into Earth, wiping out non-avian dinosaurs along with three-quarters of all other plant and animal species. Afterward, fungi began covering everything, feeding on the dying and the dead. Small mammals survived, eventually evolving into primates, eventually evolving into us. Why did they survive? Besides being small, which helped, they were warm-blooded. Fungi like it cold.
But Earth is warming. And fungi may be evolving to like it warmer.
Fungal pathogens also proliferate as we stir and remix nature on a grand scale, allowing them to be transported to novel places. Away from their native habitat, which had kept them in check, pathogens find new hosts and thrive. Every year, for example, 200 million captured animals are imported into the United States. These birds, fish, monkeys, reptiles, amphibians, and spiders find their way to restaurants, research labs, and especially pet stores. For most of these animals, no requirements exist for identifying or controlling pathogens. This legal traffic is a conveyer belt, some scientists say, loaded with viruses, bacteria, and fungi.
We humans have not yet experienced a fungal pandemic, but the same cannot be said of animals and plants. Monosson devotes several gruesome chapters to fungal infections that have devastated other species. The great frog die-off of the past 20 years saw several species (blue poison dart frogs, White’s tree frogs, green and black tree frogs, mountain yellow-legged frogs) decimated by the skin-eating chytrid fungus Batrachochytrium dendrobatidis. White pine blister rust (caused by Cronartium ribicola) has killed millions of pine trees. In the early 1900s, the American chestnut blight (Cryphonectria parasitica) reduced perhaps four billion majestic trees to stumps. And white-nose syndrome (Pseudogymnoascus destructans) has, since 2007, killed millions of bats (little brown, big brown, northern long-eared, tricolored, and Indiana).
So far, we humans have been spared this level of pathogenic fungal devastation. Will we be spared forever? Monosson’s answer is unequivocal: Get ready. Ways to do this include increasing crop and seed diversity, reversing the trend of breeding grains and other food plants for desirable qualities, in the process drastically reducing genetic diversity. More plant diversity would improve the likelihood that some individuals would be able to develop resistance to a pathogen, thus saving a species from extinction. Extensive inspections at border crossings and more effective testing and disease monitoring are also imperative. The Covid-19 pandemic made abundantly clear our vulnerabilities.
The good news is that scientists and others are working (struggling might be a better word) to put into place systems and policies to head off a new pandemic that could make Covid look like child’s play. In this terrifying book, Monosson gives us the opportunity to wise up and join their efforts.
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