Sporothrix brasiliensis: A Drug-Resistant Fungal Threat Spreading Across South America

Health officials are sounding the alarm over a drug-resistant fungal infection, Sporothrix brasiliensis, which has infected over 11,000 people and killed thousands of cats in South America since the 1990s, according to the U.S. Centers for Disease Control and Prevention (CDC). The fungus, which causes painful skin ulcers in cats and can spread to humans, is now raising concerns about its potential arrival in the United States.

What Is Sporothrix brasiliensis?

Sporothrix brasiliensis is a dimorphic fungus, meaning it exists in two forms: a mold in the environment and a yeast inside the body. It is closely related to Sporothrix schenckii, the fungus responsible for sporotrichosis, or “rose grower’s disease.” However, S. brasiliensis has unique transmission methods that make it particularly concerning.

First identified in Brazil in the 1990s, the fungus has since spread to Paraguay, Chile, Argentina, and Uruguay. It primarily infects cats, causing oozing skin ulcers, swollen lymph nodes, and, without treatment, fatal systemic infections. Humans can contract the disease through cat bites, scratches, or contact with infected feline secretions.

How Does Sporothrix brasiliensis Spread?

The fungus spreads through direct contact with infected cats, particularly during grooming or fighting. Unlike other dimorphic fungi, which typically infect humans via inhaled spores, S. brasiliensis can transmit in its yeast form. This allows it to spread through cat saliva, nasal secretions, and even contaminated surfaces.

Research published in *Medical Mycology* in 2022 found that infected cats can sneeze out infectious yeast particles, which can linger on surfaces for up to 10 weeks, according to a 2025 study in the *Brazilian Journal of Veterinary Research*. This prolonged survival increases the risk of transmission in veterinary clinics and homes.

Why Is This Fungus a Global Health Concern?

Health officials are particularly worried about the fungus’s potential to cross borders. “All it takes is one traveler bringing their cat from South America,” said Shawn Lockhart, a senior adviser at the CDC, during a presentation at the ASM Microbe meeting. “This is something we are very, very worried about.”

The fungus has already reached the United Kingdom. In 2022, a family that moved from Brazil to the UK developed the disease three years later, with one of their cats testing positive. A veterinarian who treated the cat also became infected, highlighting the risk to pet care professionals.

What Makes This Fungus Unique?

Sporothrix brasiliensis differs from other fungi in its ability to survive on surfaces for extended periods. While Candida albicans, a common yeast, lasts 48 hours on surfaces, and Candida auris, a drug-resistant fungus, survives about a month, S. brasiliensis can persist for up to 10 weeks. However, it is easily killed by bleach and ethanol, according to Lockhart.

The fungus’s transmission through cat behavior—grooming, fighting, and sneezing—also contributes to its spread. “Half of the human cases I see are people trying to administer pills to their cats and getting scratched or bitten in the process,” Lockhart said.

What Are the Risks in the United States?

While S. brasiliensis has not been reported in the U.S., health officials are preparing for its potential arrival. The lack of a commercial diagnostic test for the fungus and the absence of mandatory health certifications for imported pets increase the risk of undetected spread.

Lockhart urged veterinarians to report suspected cases of sporotrichosis to public health labs or the CDC. “There is an opportunity for it to spread quite easily,” he said. “We need veterinarians working with infection prevention and public health to make sure that this doesn’t get here.”

How Can People Protect Themselves?

Prevention focuses on reducing exposure to infected cats. Pet owners should avoid contact with stray or sick cats and seek veterinary care for any unusual skin lesions in their animals. Veterinarians are advised to use strict disinfection protocols, as the fungus can survive on surfaces for weeks.

For those who handle cats, wearing gloves and washing hands thoroughly after contact can minimize risk. Public health agencies are also working to raise awareness about the disease, particularly in regions with large cat populations.

What’s Next for Sporothrix brasiliensis Research?

Scientists are studying the fungus’s genetic makeup to better understand its drug resistance and transmission patterns. Researchers at the CDC and Brazilian institutions are collaborating on diagnostic tools and treatment guidelines. However, the lack of a commercial test remains a significant barrier to early detection.

As global travel and pet importation continue to rise, health officials emphasize the need for vigilance. “This is not a question of if, but when,” Lockhart said. “We need to be prepared.”