Marvel and DC universes have various villains, similar to infections, which also come in different shapes, sizes, and abilities. Among these infectious supervillains, like bacteria and viruses, fungi have their own place—say Poison Ivy from Batman. Fungal infections are often more obstinate and difficult to treat than viral and bacterial infections. This is because fungi can form resistant spores that evade antifungal treatments, they grow more slowly than bacteria making treatment take longer, and they can invade deep tissues, hiding from immune defenses and medications. These factors contribute to fungal infections persisting and recurring even after treatment.
As a dog parent, it’s important to understand the different types of infections that can affect your furry friend. While bacterial and viral infections get a lot of attention, every dog parent should know about common fungal infections.
What Are Fungal Infections?
Fungal infections happen when harmful fungi grow in or on your dog’s body. These infections can be either local (affecting just one area) or systemic (spreading throughout the body). Unlike bacteria, fungi are more complex organisms that can be harder to treat and may take longer to clear up.
Common Local Fungal Infections
Ringworm is probably the most well-known local fungal infection in dogs. Despite its name, it’s not actually caused by worms. This infection affects the skin, hair, and nails, causing circular patches of hair loss, scaling, and sometimes red, irritated skin. Ringworm is highly contagious and can spread to other animals and even humans.
Yeast infections are another common local problem, especially in dogs with floppy ears or skin folds. These infections often affect the ears, paws, and skin creases. You might notice your dog scratching more than usual, a musty smell, or dark, waxy discharge from the ears.
Malassezia dermatitis is a skin condition caused by yeast that naturally lives on your dog’s skin. When it overgrows, it causes itching, greasy skin, and a distinct odor.
Common Systemic Fungal Infections
Systemic infections are more serious because they affect internal organs. These infections are less common but can be life-threatening.
Blastomycosis is found mainly in certain geographic areas, particularly around the Great Lakes and river valleys. Dogs usually get infected by breathing in fungal spores from soil. Symptoms can include coughing, difficulty breathing, fever, and weight loss.
Histoplasmosis occurs when dogs inhale spores from soil contaminated with bird or bat droppings. This infection primarily affects the lungs but can spread to other organs. Signs include coughing, fever, and loss of appetite.
When to See Your Veterinarian
If you notice any unusual symptoms like persistent coughing, skin problems, ear issues, lethargy, or loss of appetite, it’s important to contact your veterinarian right away. Fungal infections can look similar to other conditions, so proper testing is needed for an accurate diagnosis.
Your vet may need to perform skin scrapings, fungal cultures, blood tests, or other diagnostic procedures to identify the specific type of infection and determine the best treatment plan.
When Nora Bruhn bought admission to the Lightning in a Bottle arts and music festival on the shores of Kern County’s Buena Vista Lake earlier this spring, her ticket never mentioned she might end up with a fungus growing in her lungs.
After weeks of night sweats, “heaviness and a heat” in her left lung, a cough that wouldn’t quit and a painful rash on her legs, her physician brother said she might have valley fever, a potentially deadly disease caused by a dust-loving fungus that lives in the soils of the San Joaquin Valley.
Bruhn said she hadn’t been warned beforehand that Kern County and Buena Vista Lake are endemic for coccidioides — the fungus that causes the disease.
“If there had been a warning that there’s a potentially lethal fungal entity in the soil, there’s no way I would have gone,” said the San Francisco-based artist. “Honestly, I would have just been paranoid to breathe the whole entire time I was there.”
The incidence and range of valley fever has grown dramatically over the last two decades, and some experts warn that the fungus is growing increasingly resistant to drugs — a phenomenon they say is due to the spraying of antifungal agents on area crops.
As annual cases continue to rise, local health officers have sought to increase awareness of the disease and its symptoms, which are often misdiagnosed. This messaging however focuses only on Kern County and other Central Valley locations and rarely reaches those who live outside Kern County, or other high-risk areas.
In the case of the Lightning in a Bottle festival, Bruhn said she wasn’t provided with any information about the risk on her ticket, or in materials provided to her by the event organizers. As far as she can recall, there were no signs or warnings at the site where she ate, slept, danced and inhaled dust for six straight days.
And she wasn’t the only one infected. According to state health officials, 19 others were diagnosed with coccidioidomycosis in the weeks and months following the event. Five were hospitalized.
According to a statement provided by the California Department of Public Health, officials have been in communication with organizers and “encouraged” them to notify “attendees about valley fever and providing attendees with recommendations to follow up with healthcare providers if they develop illness.”
Do LaB, the company that stages the festival, said through a spokesperson that it adheres to the health and safety guidance provided by federal, state and local authorities. “Health and safety is always the primary concern,” they said.
The company’s website warns festivalgoers about the prevalence of dust — but doesn’t mention the fungus or the disease.
“Some campgrounds and stage areas will be on dusty terrain,” the website says. “We strongly recommend that everyone bring a scarf, bandana, or dust mask in case the wind kicks up! We also recommend goggles and sunglasses.”
Bruhn said that’s not enough.
“I think it’s really irresponsible to have a festival in a place where breathing is possibly a life-threatening act,” she said.
Kern County’s health department is also in discussions with the production company.
Kern County’s Buena Vista Lake was the site of the Lightning in a Bottle festival this spring.
(Nora Bruhn)
In California, the number of valley fever cases has risen more than 600% since 2000. In 2001, fewer than 1,500 Californians were diagnosed. Last year, that number was more than 9,000.
Most people who are infected will not experience symptoms, and their bodies will fight off the infection naturally. Those who do suffer symptoms however are often hard-pressed to recognize them, as they resemble the onset of COVID or the flu. This further complicates efforts to address the disease.
Take for example the case of Brynn Carrigan, Kern County’s director of public health.
In April, Carrigan began getting a lot of headaches. Not really a “headache person,” she chalked them up to stress: Managing a high-profile public health job while also parenting two teenagers. But as the days and weeks went by, the headaches became more frequent, longer in duration and increasingly painful. She also developed an agonizing sensitivity to light.
“I’ve never experienced sensitivity to light like that … all the curtains in my house had to be closed. I was wearing sunglasses inside — because even the clock on my microwave and my oven, and the cable box … oh, my God, it caused excruciating pain,” she said. In order to leave the house, she had to put a blanket over her head because the pain caused by sunlight was unbearable.
She also developed nausea and began vomiting, which led to significant weight loss. Soon she became so exhausted she couldn’t shower without needing to lie down and sleep afterward.
Her doctors ordered blood work and a CT scan. They told her to get a massage, suggesting her symptoms were the result of tension. Another surmised her symptoms were the result of dehydration.
Eventually, it got so bad she was hospitalized.
When test results came in, her doctors told Carrigan she had a case of disseminated valley fever, a rare but very serious form of the disease that affects the brain and spine rather than the lungs. In retrospect, she said she probably had the disease for months.
Valley fever, a fungal infection, spreads through dust.
(Jason Armond/Los Angeles Times)
And yet, here she was, arguably the most high-profile public health official in a county recognized as a hot spot for the fungus and the disease, misdiagnosed by herself and other health professionals repeatedly before someone finally decided to test her for the fungus.
Now she’ll have to take expensive antifungal medications for the rest of her life — medication that has resulted in her losing her hair, including her eyelashes, as well as making her skin and mouth constantly dry.
As a result of Carrigan’s experience, her agency is running public service announcements on TV, radio and in movie theaters. She does news conferences, talks to reporters and runs presentations for outdoor workforces — solar farms, agriculture and construction — to educate those “individuals that have no choice but to be outside and really disturbing the soil.” She’s also hoping to get in schools.
But she realizes her influence is geographically constrained. She can really only speak to the people who live there.
For people who come to Kern County for a visit — like Bruhn and the 20,000 other concertgoers who attended Lightning in a Bottle this year — once they leave, they’re on their own.
A truck raises dust on a dirt road in Bakersfield in March 2022.
(Jason Armond/Los Angeles Times)
Outside of California, valley fever is also prevalent in Arizona and some areas of Nevada, New Mexico, Utah and Texas, as well as parts of Mexico and Central and South America
Experts worry that as the range of valley fever spreads — whether by a changing climate, shifting demographics, or increased construction in areas once left to coyotes, desert rodents and cacti — more and more severe cases will appear.
They’re also concerned that the fungus is building resistance to the medicines used to fight it.
Antje Lauer, a professor of microbiology at Cal State Bakersfield and a “cocci” fungus expert, said she and her students have found growing pharmaceutical resistance in the fungus, the result of the use of agricultural fungicides on crops.
She said the drug fluconazole — the fungicide doctors prescribe off-label to treat the disease — is nearly identical in molecular structure to the antifungal agents “being sprayed against plant pathogens. … So when a pathogen gets exposed via those pesticides, the valley fever fungus is also in those soils. It gets exposed and is building an immunity.”
It’s the kind of thing that really concerns G.R. Thompson, a professor of medicine at UC Davis and an expert in the treatment of valley fever and other fungal diseases.
“If you ask me, what keeps you up at night about valley fever or fungal infections?, it’s what we do to the environment” he said. “We learned that giving chickens and livestock antibiotics was bad, because even though they grew faster, it led to antibiotic resistance. Right now, we’re kind of having our own reckoning with fungal infections in the environment. We’re putting down antifungals on our crops, and now our fungi are become resistant before our patients have ever even been treated.”
He said he and other health and environment professionals are working with various local, state and federal agencies “to make sure that everybody’s talking to each other. You know that what we’re putting down on our crops is not going to cause problems in our hospitals.”
Because at the same time, he said, there’s a growing concern that the fungus has become more severe in terms of clinical outcomes.
“We’re seeing more patients in the hospital this year than ever before, which has us wondering … has the fungus changed?” he said, quickly adding that health experts are actively investigating this question and don’t have an answer.
John Galgiani, who runs the Valley Fever Center for Excellence out of the University of Arizona in Tucson, is hopeful that a vaccine may be forthcoming.
He said a Long Beach-based medical startup called Anivive got a contract to take a vaccine that’s being developed for dogs — outdoor-loving creatures with noses to the ground and a penchant for digging, and therefore susceptible to the disease — and reformulate it to make it suitable for human clinical trials.
He said prison populations, construction workers, farmworkers, firefighters, archaeologists — anyone who digs in the soil, breaths it in or spends time outdoors in these areas — would be suitable populations for such inoculations.
But he, like everyone else The Times spoke with, believes education and outreach are the most important tools in the fight against the disease.
As there is with any other risky activity, he said, if people are aware, such knowledge empowers them with choice — and in this case, the tools they need to help themselves should they fall ill.
California health officials are urging people who attended the Kern County music festival Lightning in a Bottle to seek medical care if they are experiencing respiratory symptoms or a fever.
Authorities have identified five patients with valley fever who attended the six-day event, which was held May 22-27 at Buena Vista Lake, near Bakersfield. Three people have been hospitalized.
More than 20,000 people attended the festival.
One attendee, on a Reddit r/LightningInaBottle thread, said a festival companion had been hospitalized for two weeks with “severe” valley fever.
“If you get unexplainable symptoms such as fever, chills, and headaches/neck pain,” the user wrote, “let the doctors know it could be valley fever, even though it’s been several months.”
Valley fever is an infectious disease caused by the coccidioides fungus, which grows in the soil and dirt in some areas of California. It is most commonly found in the San Joaquin Valley and Central Coast of California.
Health officials say that most people exposed to this fungus don’t end up developing the disease, but it can infect the lungs and cause respiratory symptoms in some people, including cough, difficulty breathing, fever and fatigue.
In rare cases, the fungus can spread to other parts of the body and cause severe disease.
Valley fever is not contagious. Past outbreaks have been linked to dust and dirt exposure at outdoor events and job sites where dirt is disturbed — in areas of the state where the fungus is common.
Valley fever is on the rise in California, with particularly high numbers of cases reported in 2023 and 2024. The fungus appears to flourish in wet years.
A 2022 study in the medical journal the Lancet concluded that multiyear cycles of dry conditions followed by wet winters increased transmission, especially in areas that were historically wetter. Climate change is expected to increase the frequency and duration of drought throughout the Southwestern United States, potentially increasing the prevalence of valley fever spores and fungus.
Kern County has the highest incidence rate in the state, and it accounts — on average — for about a third of the cases.
State health officials say that people who have visited Kern County in recent months and are experiencing respiratory symptoms that have not improved or are lasting longer than a week should see a healthcare provider and ask about possible valley fever.
They also urge people to mention attendance at the music festival or travel to Kern County.
Attendees can visit the California Department of Public Health’s valley fever survey website for more information and to share details about any illness.
Another Reddit user said they came down with the disease two weeks after returning from the festival to their home in Colorado.
The music fan described a “terrible” cough, headache, body aches, fever and chills. The Reddit user is not sure they’d go again next year.
“Don’t want to miss … but I also don’t want a fungal lung infection again. Yikes.”
Back at the turn of the 21st century, valley fever was an obscure fungal disease in the United States, with fewer than 3,000 reported cases a year, mostly in California and Arizona. Two decades later, cases of valley fever have exploded, increasing roughly sevenfold by 2019.
And valley fever isn’t alone. Fungal diseases in general are appearing in places they have never been seen before, and previously harmless or mildly harmful fungi are becoming more dangerous for people. One likely reason for this worsening fungal situation, scientists say, is climate change. Shifts in temperature and rainfall patterns are expanding where disease-causing fungi occur; climate-triggered calamities can help fungi disperse and reach more people; and warmer temperatures create opportunities for fungi to evolve into more dangerous agents of disease.
For a long time, fungi have been a neglected group of pathogens. By the late 1990s, researchers were already warning that climate change would make bacterial, viral, and parasite-caused infectious diseases such as cholera, dengue, and malaria more widespread. “But people were not focused at all on the fungi,” says Arturo Casadevall, a microbiologist and an immunologist at the Johns Hopkins Bloomberg School of Public Health. That’s because, until recently, fungi have caused humans relatively little trouble.
Our high body temperature helps explain why. Many fungi grow best at about 12 to 30 degrees Celsius (roughly 54 to 86 degrees Fahrenheit). So though they find it easy to infect trees, crops, amphibians, fish, reptiles, and insects—organisms that do not maintain consistently high internal body temperatures—fungi usually don’t thrive inside the warm bodies of mammals, Casadevall wrote in an overview of immunity to invasive fungal diseases in the 2022 Annual Review of Immunology. Among the few fungi that do infect humans, some dangerous ones, such as species of Cryptococcus, Penicillium, and Aspergillus, have historically been reported more in tropical and subtropical regions than in cooler ones. This, too, suggests that climate may limit their reach.
Today, however, the planet’s warming climate may be helping some fungal pathogens spread to new areas. Take valley fever, for instance. The disease can cause flu-like symptoms in people who breathe in the microscopic spores of the fungus Coccidioides. The climatic conditions favoring valley fever may occur in 217 counties of 12 U.S. states today, according to a 2019 study by Morgan Gorris, an Earth-system scientist at the Los Alamos National Laboratory, in New Mexico.
But when Gorris modeled where the fungi could live in the future, the results were sobering. By 2100, in a scenario where greenhouse-gas emissions continue unabated, rising temperatures would allow Coccidioides to spread northward to 476 counties in 17 states. What was once thought to be a disease mostly restricted to the southwestern U.S. could expand as far as the U.S.-Canadian border in response to climate change, Gorris says. That was a real “wow moment,” she adds, because that would put millions more people at risk.
Some other fungal diseases of humans are also on the move, such as histoplasmosis and blastomycosis. Both, like valley fever, are seen more and more outside what was thought to be their historical range.
Such range extensions have also appeared in fungal pathogens of other species. The chytrid fungus that has contributed to declines in hundreds of amphibian species, for example, grows well at environmental temperatures from 17 to 25 degrees Celsius (63 to 77 degrees Fahrenheit). But the fungus is becoming an increasing problem at higher altitudes and latitudes, which likely is in part because rising temperatures are making previously cold regions more welcoming for the chytrid. Similarly, white-pine blister rust, a fungus that has devastated some species of white pines across Europe and North America, is expanding to higher elevations where conditions were previously unfavorable. This has put more pine forests at risk. Changing climatic conditions are also helping drive fungal pathogens of crops, like those infecting bananas and wheat, to new areas.
A warming climate also changes cycles of droughts and intense rains, which can increase the risk of fungal diseases in humans. One study of more than 81,000 cases of valley fever in California from 2000 to 2020 found that infections tended to surge in the two years immediately following prolonged droughts. Scientists don’t yet fully understand why this happens. But one hypothesis suggests that Coccidioides survives better than its microbial competitors during long droughts, then grows quickly once rains return and releases spores into the air when the soil begins to dry again. “So climate is not only going to affect where it is, but how many cases we have from year to year,” says Gorris.
By triggering more intense and frequent storms and fires, climate change can also help fungal spores spread over longer distances. Researchers have found a surge in valley-fever infections in California hospitals after large wildfires as far as 200 miles away. Scientists have seen this phenomenon in other species too: Dust storms originating in Africa may be implicated in helping move a coral-killing soil fungus to the Caribbean.
Researchers are now sampling the air in dust storms and wildfires to see if these events can actually carry viable, disease-causing fungi for long distances and bring them to people, causing infections. Understanding such dispersal is key to figuring out how diseases spread, says Bala Chaudhary, a fungal ecologist at Dartmouth who co-authored an overview of fungal dispersal in the 2022 Annual Review of Ecology, Evolution, and Systematics. But there’s a long road ahead: Scientists still don’t have answers to several basic questions, such as where various pathogenic fungi live in the environment or the exact triggers that liberate fungal spores out of soil and transport them over long distances to become established in new places.
Helping existing fungal diseases reach new places isn’t the only effect of climate change. Warming temperatures can also help previously innocuous fungi evolve tolerance for heat. Researchers have long known that fungi are capable of this. In 2009, for example, researchers showed that a fungus—in this case, a pathogen that infects insects—could evolve to grow at nearly 37 degrees Celsius, some five degrees higher than its previous upper thermal limit, after just four months. More recently, researchers grew a dangerous human pathogen, Cryptococcus deneoformans, at both 37 degrees Celsius (similar to human body temperature) and 30 degrees Celsius in the lab. The higher temperature triggered a fivefold rise in a certain type of mutation in the fungus’s DNA compared with the lower temperature. Rising global temperatures, the researchers speculate, could thus help some fungi rapidly adapt, increasing their ability to infect people.
There are examples from the real world too. Before 2000, the stripe-rust fungus, which devastates wheat crops, preferred cool, wet parts of the world. But since 2000, some strains of the fungus have become better adapted to higher temperatures. These sturdier strains have been replacing the older strains and spreading to new regions.
This is worrying, says Casadevall, especially with hotter days and heat waves becoming more frequent and intense. “Microbes really have two choices: adapt or die,” he says. “Most of them have some capacity to adapt.” As climate change increases the number of hot days, evolution will likely select more strongly for heat-resistant fungi.
And as fungi in the environment adapt to tolerate heat, some might even become capable of breaching the human temperature barrier.
This may have happened already. In 2009, doctors in Japan isolated an unknown fungus from the ear discharge of a 70-year-old woman. This new-to-medicine fungus, which was given the name Candida auris, soon spread to hospitals around the world, causing severe bloodstream infections in already sick patients. The World Health Organization now lists Candida auris in its most dangerous group of fungal pathogens, partly because the fungus is showing increasing resistance to common antifungal drugs.
“In the case of India, it’s really a nightmare,” says Arunaloke Chakrabarti, a medical mycologist at the Postgraduate Institute of Medical Education and Research in Chandigarh, India. When C. auris was first reported in India more than a decade ago, it was low on the list of Candida species threatening patients, Chakrabarti says, but now, it’s the leading cause of Candida infections. In the U.S., clinical cases rose sharply from 63 in the period from 2013 to 2016 to more than 2,300 in 2022.
Where did C. auris come from so suddenly? The fungus appeared simultaneously across three different continents. Each continent’s version of the fungus was genetically distinct, suggesting that it emerged independently on each continent. “It’s not like somebody took a plane and carried them,” says Casadevall. “The isolates are not related.”
Because all continents are exposed to the effects of climate change, Casadevall and his colleagues think that human-induced global warming may have played a role. C. auris may always have existed somewhere in the environment—potentially in wetlands, where researchers have recovered other pathogenic species of Candida. Climate change, they argued in 2019, may have exposed the fungus to hotter conditions over and over again, allowing some strains to become heat-tolerant enough to infect people—although the researchers cautioned that many other factors are also likely at play.
Subsequently, scientists from India and Canada found C. auris in nature on the Andaman Islands in the Bay of Bengal. This “wild” version of C. auris grew much slower at human body temperature than did the hospital versions. “What that suggests to me is that this stuff is all over the environment and some of the isolates are adapting faster than others,” says Casadevall.
Like other explanations for C. auris’s origin, Casadevall’s is only a hypothesis, says Chakrabarti, and still needs to be proved.
One way to establish the climate-change link, Casadevall says, would be to review old soil samples and see whether they have C. auris in them. If the older versions of the fungus don’t grow well at higher temperatures, but over time they start to, that would be good evidence that they’re adapting to heat.
In any case, the possibility of warmer temperatures bringing new fungal pathogens to humans needs to be taken seriously, says Casadevall—especially if drug-resistant fungi that currently infect species of insects and plants become capable of growing at human body temperature. “Then we find ourselves with organisms that we never knew before, like Candida auris.”
Doctors are already encountering novel fungal infections in people, such as multiple new-to-medicine species of Emergomyces that have appeared mostly in HIV-infected patients across four continents, and the first record of Chondrostereum purpureum—a fungus that infects some plants of the rose family—infecting a plant mycologist in India. Even though these emerging diseases haven’t been directly linked to climate change, they highlight the threat that fungal diseases might pose. For Casadevall, the message is clear: It’s time to pay more attention.
