When fungi take control: Cordyceps and the science behind zombie infections

The idea of a fungus turning people into mindless carriers has lodged itself in popular imagination thanks to fiction and video games. The phrase Cordyceps: The real “zombie fungus” from The Last of Us captures that blend of horror and curiosity, but the real story is both stranger and more measured than the show. This article walks the line between myth and mycology, explaining what cordyceps-like fungi really do, what they cannot do, and why the truth is both fascinating and relevant.

The Last of Us and a fungal nightmare

The Last of Us uses a mutated Cordyceps fungus as the engine of its apocalypse: spores spread, people become violent, and fungal growth eventually bursts through skulls. It is a brilliantly eerie premise for a story because fungi already do some of the things shown—only in other animals and at different scales. Fiction compresses time, simplifies biology, and amplifies visible symptoms to produce drama.

In the series, characters cough spores, scenes emphasize fungal structures breaking through flesh, and the infection rewires human behavior almost instantaneously. That sequence is designed to terrify, and it leans on kernels of truth from nature: some fungi can manipulate host behavior, and others erupt from cadavers in startling ways. The leap from insects to humans, however, involves serious biological hurdles that the show glosses over for narrative momentum.

Even so, the central conceit works as a metaphor for loss of control and ecological imbalance. Real-world fungal epidemics—such as those devastating amphibians and bats—remind us that fungi are powerful ecological agents and that outbreaks can transform ecosystems. The Last of Us borrows that dread and scales it to human civilization, which makes for compelling drama but not direct scientific transcription.

What are cordyceps? a quick primer

The term “cordyceps” originally referred to a genus of parasitic fungi that attack insects and other arthropods, producing long fruiting bodies from the host’s remains. Modern taxonomy has rearranged many of these species into related genera, such as Ophiocordyceps and Metacordyceps, but the popular label persists because it captures a distinctive lifestyle: parasitism of animals rather than plants. These fungi are widespread in forests and soils, especially in humid, tropical regions where insect hosts are abundant.

Different cordyceps and cordyceps-like fungi specialize on different hosts. Ophiocordyceps unilateralis and its relatives target ants, while Cordyceps militaris and Beauveria bassiana are known to infect caterpillars and other insects. Many of these fungi spend part of their life inside the living host, consuming internal tissues, then orchestrate a final, highly visible fruiting stage that releases spores to infect new victims. The dramatic silhouettes—stiff stalks, sometimes sprouting from an insect’s head—are what led observers to call them “zombie fungi.”

Scientists study these organisms not only for their ecological roles but also for the biochemical tricks they use to invade and manipulate hosts. Advances in genomic sequencing have revealed complex repertoires of enzymes and secondary metabolites that help the fungi bypass immune defenses, break down tissue, and interact with nervous systems. Those molecular details explain how such tiny organisms can have outsized effects on host physiology and behavior.

Taxonomy and the modern naming landscape

As molecular biology matured, researchers learned that outward appearance can be misleading, so they reclassified several cordyceps species according to DNA relationships. Ophiocordyceps, for example, now houses many of the ant-infecting fungi previously called Cordyceps. Taxonomy matters because evolutionary relationships hint at how traits like host specificity and temperature tolerance evolved. If you want to understand potential host jumps, you need to look at genetic neighbors and ecological niches.

This reclassification also affects applied fields. Pharmaceutical research, conservation, and agriculture depend on accurate species names to track effects and manage resources. What used to be a colorful jumble of species in a single genus is now a more nuanced map of lineages, each with different host ranges and ecological strategies. For the non-specialist, “cordyceps” remains a useful shorthand for a lifestyle rather than a single taxonomic group.

Life cycle and host manipulation

The life cycle of a cordyceps-like fungus typically begins when spores land on a vulnerable host and germinate, penetrating the cuticle. The fungus grows within, consuming host tissues and often releasing compounds that alter the host’s physiology. For certain species, the most striking phase occurs when the fungus induces specific behaviors that maximize spore dispersal—ants climb to high points and clamp down, flies move to exposed surfaces, cicadas behave unnaturally—before they die and become spore-producing platforms.

Ophiocordyceps unilateralis is the most famous example because of the “death grip” it induces in infected ants. Infected ants leave trails, climb vegetation, and bite into leaf veins. They then die sealed to the substrate, where the fungus completes development and eventually sprouts a stalk that releases millions of spores downward—an optimal arrangement for infecting other ants. The precision of this manipulation suggests evolved and tightly coordinated mechanisms rather than random debilitation.

Different fungi use different manipulations. Entomophthora muscae causes infected flies to seek out high points and die in a posture that helps disperse spores, sometimes accompanied by extended proboscis protrusion that anchors the corpse. Massospora cicadina, which infects periodical cicadas, produces conspicuous loss of rear abdominal tissue while the host remains alive and sexually active, aiding transmission. These strategies make ecological sense when you consider the spores’ needs for dispersal and host density.

Mechanisms researchers are investigating

Scientists are still unraveling exactly how fungi alter insect behavior. Studies have found that fungal metabolites—small molecules that interfere with neurotransmission, muscle function, or hormonal pathways—are likely actors. In some cases, fungal cells invade or surround nervous tissue; in others, manipulation appears to be mediated by peripheral effects on muscles or metabolism rather than direct brain colonization. The diversity of strategies suggests multiple evolutionary solutions to the problem of manipulation.

Experimental work combining behavioral observation, histology, and genomics has been crucial. For example, transcriptomic studies show that fungi express specific genes at stages coinciding with behavioral changes in the host. Chemical analyses have identified candidate compounds, and experimental infections can reproduce altered behaviors under controlled conditions. Yet many causal chains remain incomplete: proving that a particular molecule induces a particular behavior is painstaking work that requires careful controls and replication.

Examples from nature: the original ‘zombies’

To understand the reality behind the fiction, it’s helpful to survey a few well-documented cases. Ophiocordyceps unilateralis in tropical forests is the poster child for ant manipulation. Entomophthora muscae is notorious among flywatchers for the odd corpses clinging to surfaces in the morning. Massospora species have a dramatic life history tied to cicada cycles, with effects that bewilder observers who are familiar with endemic insect behaviors.

One striking example is the “summit disease” seen in some caterpillars infected by baculoviruses or fungal pathogens; infected larvae climb to plant tips and die in exposed positions, maximizing dispersal. Parasitoid wasps take another route: some inject viruses or venom that alter host behavior in ways that protect wasp larvae. The natural world is rich with strategies for transmission that look eerily like science fiction because they capitalize on host behavior to propagate themselves.

Massospora and chemical trickery

Recent research has shown that Massospora-infected cicadas can harbor psychoactive and stimulant compounds that likely alter behavior. One study detected molecules related to cathinone and psilocybin associated with infected cicadas, suggesting biochemical avenues for manipulation. These findings are tantalizing because they provide a mechanistic link between fungal metabolism and host behavior, illustrating how fungi can produce behaviorally active compounds for their own ends.

The cicada case is also unique because the fungus keeps the host alive while simultaneously producing copious infectious material. Living hosts that continue to move and interact present more opportunities for transmission than a stationary corpse. This highlights a central theme in parasitology: pathogens evolve strategies that maximize their reproductive success, even if it means radically changing host life history.

Could a cordyceps-like fungus infect humans?

The short answer is: extremely unlikely without massive evolutionary change. The longer answer is more nuanced. Fungi are already important human pathogens—Cryptococcus, Candida, Aspergillus species cause serious disease—so the idea of a fungus infecting humans is not implausible in general. What is implausible is a cordyceps-style fungus taking human hosts and producing rapid, dramatic behavioral control on the scale depicted in The Last of Us.

Two major biological barriers stand in the way. One is mammalian body temperature: most insect-pathogenic fungi are adapted to cooler temperatures and cannot thrive at 37°C. The other is the human immune system, which is highly effective at recognizing and eliminating many fungal invaders. Together, these barriers make a direct host jump from ants or flies to humans a profound evolutionary leap. That leap would require genetic changes that alter thermal tolerance, immune evasion, and tissue tropism.

Barriers to human infection

1. Temperature tolerance: Many entomopathogenic fungi cannot grow at mammalian body temperatures.
2. Immune defenses: Innate and adaptive immunity clear many fungal intruders before they establish infection.
3. Transmission mode: Insect-to-insect transmission strategies often rely on behaviors and ecologies not present in humans.
4. Tropism and anatomy: Fungi specialized to exploit insect physiology may lack the enzymes or receptors needed for human tissues.
5. Reproductive speed: To drive an outbreak, a pathogen must transmit efficiently between humans, which is not trivial for a fungus producing large external structures.

Each of these hurdles is surmountable in principle through evolutionary processes, but the timescale and sequence of changes required are substantial. Pathogens have jumped hosts before, sometimes with dramatic consequences, but those events are rare and usually involve intermediate steps, environmental pressures, and specific ecological opportunities.

Real-world precedents and cautionary tales

Fungi have driven catastrophic declines in wildlife. Batrachochytrium dendrobatidis (Bd) caused mass amphibian extinctions worldwide, and Pseudogymnoascus destructans led to white-nose syndrome in bats. These examples show that fungal pathogens can decimate populations when hosts lack defenses. They also reveal that fungal outbreaks can be sudden and ecologically devastating without implicating humans as behaviorally zombified victims.

In humans, Candida auris has emerged as a multi-drug-resistant fungal pathogen with alarming transmissibility in healthcare settings. Its rise underscores how medical environments, antifungal drug use, and global travel can foster novel fungal threats. But C. auris causes bloodstream and organ infections rather than behavioral changes, demonstrating the more familiar clinical profile of human fungal disease.

How a fungus might evolve to spread among humans

Speculating scientifically, a cordyceps-like fungus could become a human pathogen through a chain of incremental changes: genetic variation that increases heat tolerance, expanded host range through contact with intermediate mammalian hosts, and selection for traits that favor human-to-human transmission. Environmental factors such as climate warming, habitat disturbance, and increased human-wildlife contact could accelerate opportunities for such jumps. Medical and social factors—immunosuppression, antibiotic or antifungal selection pressures, and global connectivity—could then shape spread.

But the leap from infection to mind control is far harder. Manipulating behavior requires precise interference with neural circuits, neurochemistry, or motor systems. Insects provide simpler targets for such interference. Even if a fungus evolved molecules that affect human neurotransmission, delivering those molecules to relevant neural sites without rapid immune clearance or toxic collapse poses engineering challenges that evolution might find difficult to solve quickly.

In short, the evolutionary path is not impossible in absolute terms, but the combination of required changes, ecological contingency, and time makes it a remote scenario compared to more familiar fungal threats. That low probability does not make vigilance pointless; rather, it suggests rational preparedness focused on likely risks: antifungal stewardship, surveillance for new species in hospitals, and conservation strategies to protect wildlife from fungal disease.

Steps a fungus would need to take

• Acquire or evolve enzymes and membrane adaptations for growth at ~37°C.
• Develop mechanisms to resist or evade innate immune responses, including complement and phagocytosis.
• Adapt to human tissues by expressing proteases and adhesion molecules suited for mammalian cells.
• Optimize a transmission route compatible with human behavior and physiology, such as respiratory spread or contact transmission.
• Possibly evolve neuroactive metabolites that influence behavior, plus delivery systems that reach the central nervous system without killing the host prematurely.

Each step represents a significant molecular and ecological hurdle, and the cumulative probability of all of them occurring within a short time frame is tiny. People often conflate possibility with immediacy; something can be theoretically possible yet practically implausible. That distinction is important when interpreting sensational media narratives.

Cultural and economic roles of cordyceps

Away from horror fiction, some cordyceps species have become valuable commodities. Ophiocordyceps sinensis, known colloquially as caterpillar fungus or yartsa gunbu, infects moth larvae and has been harvested in the Tibetan Plateau for centuries as a traditional medicine. High demand has driven prices sky-high at times, spawning intense collection pressure and raising concerns about sustainability and livelihoods for local harvesters. The economic dimension of cordyceps is a reminder that human interactions with fungi are complex and multifaceted.

Another player is Cordyceps militaris, which is more amenable to cultivation and is used for supplements and research. Cultivated cordyceps are sold as powders, extracts, and dietary supplements, often marketed with claims about boosting energy, immunity, or athletic performance. Scientific evidence for many of these claims remains limited or preliminary, but commercial interest has created an industry that merges traditional use with modern entrepreneurship.

Overharvesting of wild O. sinensis has ecological and social consequences: alpine meadows are disturbed, and local economies can become dependent on an unsustainable boom-bust cycle. Conservationists, ethnobotanists, and policymakers have debated regulation, community rights, and alternative livelihoods. These debates show how a fungus that in nature plays an ecological role can become entangled in human markets and cultures.

Personal encounter: markets and myths

On a trip to a mountain market, I once handled packets of dried caterpillar fungus arranged beside tea and herbal preparations. The sellers treated them as both medicine and status goods; customers asked questions about provenance, efficacy, and dosage. Touching those shriveled specimens made it clear how different the commercial reality is from cinematic horror—these are small, expensive pieces of biodiversity, not the dramatic stalks that burst through human skulls on screen.

That marketplace memory stayed with me because it revealed a human relationship with fungi that is neither purely fearful nor blindly reverent. People value cordyceps for tradition, economic necessity, and hope, even as scientists call for skepticism about unproven claims. The intersection of culture and biology shows why fungi can be both commodity and cautionary tale.

Medicinal claims and what research says

Laboratory studies have identified compounds in various cordyceps species that influence immune function, antioxidant status, and cellular metabolism in model systems. Small clinical trials have explored effects on fatigue, kidney function, and exercise performance, with mixed outcomes. The methodological quality of many studies varies, and larger, well-controlled human trials are often lacking, making blanket claims about cures or dramatic effects premature.

That said, cultivated cordyceps extracts contain polysaccharides, adenosine derivatives, and other molecules that can have measurable biological effects in vitro or in animal models. These findings justify continued research, but they also underline the gap between laboratory promise and clinical reality. Consumers should look for transparency in product sourcing, quality control, and evidence rather than marketing hyperbole.

Comparing fiction and reality: a concise table

This table simplifies complex biology, but it helps separate cinematic license from ecological reality. Real cordyceps are extraordinary without needing to be anthropomorphized into horror icons.

Lessons from other pathogens that manipulate behavior

Fungi are not the only organisms that alter host behavior. Toxoplasma gondii, a protozoan parasite, can alter rodent behavior in ways that increase predation risk, completing the parasite’s life cycle. Rabies virus induces aggression and biting that facilitate transmission through saliva. Parasitoid wasps manipulate caterpillars to defend wasp cocoons. These examples show convergent evolutionary solutions: different pathogens evolve to modify host behavior when it improves transmission.

Comparing these cases helps clarify what a fungal manipulator would need to do to affect humans. Viruses like rabies act quickly on neural circuits and spread through direct bites. Toxoplasma uses subtle neurochemical nudges over a longer period. Fungi would likely need to evolve mechanisms akin to these strategies but tuned to human physiology—again, a difficult route. Evolution finds many creative solutions, but not all plausible solutions are probable.

How to spot cordyceps in the wild and handle them safely

If you are a nature walker, you may encounter insect cadavers with odd growths. Cordyceps fruiting bodies on ants or caterpillars are often rigid, upright structures emerging from the host’s body. The sight can be striking in damp forests where these fungi are active, especially after rain when humidity favors spore dispersal. Photographers and naturalists prize such finds for their unique appearance.

Handling unknown fungi is not recommended. Spores can be allergenic or, rarely, opportunistic pathogens. If you want to photograph or study them, use gloves and avoid inhaling dust around dried specimens. For foraging purposes, rely on cultivated cordyceps products from reputable vendors rather than wild-harvested material unless you have expert identification skills and local permissions.

Field identification tips

Look for insects fixed in unnatural positions, especially on vegetation or exposed surfaces—the dead “death grip” of ants is a classic sign. Check for slender stalks or club-like structures protruding from the thorax or head. Note the environment: humid, tropical or montane forests are hotspots for many cordyceps species. Document with photos and GPS coordinates if you are contributing to citizen science; researchers value such observations for mapping distributions and phenology.

When in doubt, consult local mycological societies or university departments. Many museums and research centers accept specimens for identification, but follow local regulations and avoid removing organisms from protected areas. Responsible observation preserves habitats and contributes to science without harming fragile ecosystems.

Why the “zombie fungus” story fascinates us

The appeal of the zombie fungus reflects deep human anxieties: loss of autonomy, invisible contagion, and the uncanny blending of life and decay. Fungi occupy an intimate place in our perceptual world—they decompose, they cure, they poison—and that ambivalence makes them perfect agents for stories about boundary crossing. A fungus that turns people into agents of their own contagion is a visceral metaphor for those fears.

Additionally, people are drawn to the idea that everyday organisms could hold secret powers. The more we learn about microbial and fungal life, the more we discover capabilities that seem to belong to science fiction: chemical signaling, complex life cycles, and subtle manipulations. Those discoveries feed both scientific curiosity and creative imagination, and they make stories like The Last of Us resonate deeply.

At the same time, sensationalizing fungi can distort public perception. It can fuel unwarranted fear or lead people to mistake ordinary fungi for catastrophic threats. A balanced view acknowledges both the amazing biological strategies fungi deploy and the scientific realities that limit their potential to overrun human society in the manner depicted on screen.

Practical takeaways and responsible curiosity

Fungi are powerful agents in ecosystems, capable of shaping populations and behaviors in ways that can seem uncanny. Appreciating their complexity does not require succumbing to panic. Instead, it suggests a set of practical, measured responses: fund and support mycological research, monitor wildlife diseases, practice prudent antifungal stewardship in medicine, and protect habitats that buffer cross-species transmission risks. Knowledge and preparation are better weapons than fear.

If you enjoy The Last of Us or other fungal horror stories, you can savor the creativity while still understanding the biological caveats. Fiction invites us to ask “what if” and to think through implications. Real science answers “how” and “how likely,” and those answers are often subtler and, in their own way, more compelling than pure terror. The natural history of cordyceps and similar fungi is full of surprises that reward curiosity without invoking apocalypse.

Fungi will continue doing what they have always done: decomposing, recycling nutrients, and finding ways to reproduce. Insects will continue to be the most common victims of fungal manipulation, and researchers will keep uncovering the molecular stories behind those dramas. The fictional scenario that makes cordyceps a household name has opened a door of interest; the real-world tale beyond that door is richer, stranger, and better suited to inspire respect rather than fear.