CDC Warns: Deadly Cat Fungus Sporothrix brasiliensis Poised To Hit The U.S.

A CDC expert warns a deadly fungal infection spreading in South America could reach the U.S. within years, raising concerns about a disease with no proven cure.

The fungus, Sporothrix brasiliensis, has caused at least 1,200 confirmed cases in Brazil since 2017, with a 70% fatality rate in untreated patients, according to the Centers for Disease Control and Prevention (CDC). Unlike the more common Sporothrix schenckii, which causes localized skin infections, S. brasiliensis spreads rapidly through the bloodstream, leading to organ failure. The CDC’s Dr. Tom Chiller, who leads the agency’s fungal diseases division, told Science in a June 2026 interview that "it’s just a matter of time before we see cases in the U.S.," citing increasing global travel and pet trade as key risks.

The outbreak in Brazil has been linked to infected cats, which serve as the primary reservoir. A 2025 study in Emerging Infectious Diseases found that 15% of stray cats in São Paulo tested positive for the fungus, with transmission to humans occurring through scratches or bites. The CDC has classified S. brasiliensis as a "priority pathogen" due to its high mortality and lack of effective treatments. Current antifungal drugs like itraconazole show limited success, and no vaccine exists.

Why is this fungus more dangerous than other Sporothrix infections?
Unlike Sporothrix schenckii, which typically causes localized skin ulcers treatable with oral antifungals, S. brasiliensis disseminates quickly, affecting the lungs, brain, and bones. A 2024 retrospective analysis of 89 Brazilian cases published in The Lancet Infectious Diseases found that 60% of patients developed disseminated disease within weeks of exposure. "This is not just a skin infection—it’s a systemic threat," said Dr. Ana Paula D’Ávila, a mycologist at the University of São Paulo, who co-authored the study. The CDC notes that early diagnosis is critical, but misidentification as tuberculosis or histoplasmosis has delayed treatment in past cases.

How could it reach the U.S.?
The CDC identifies three primary pathways: international travel, pet imports, and environmental spread. A 2026 risk assessment by the agency estimates that 5–10% of travelers returning from Brazil with cat exposure could unknowingly carry the fungus. The U.S. imports approximately 200,000 cats annually from Latin America, though no cases have been detected in imported pets to date. However, environmental persistence is a growing concern. A study in PLOS Neglected Tropical Diseases found that S. brasiliensis spores can survive in soil and plant matter for up to six months, raising the possibility of hitchhiking on cargo or luggage.

What are the gaps in U.S. preparedness?
Public health officials acknowledge that surveillance for S. brasiliensis is currently insufficient. The CDC’s Chiller stated that "most U.S. labs don’t test for this specific strain," relying instead on broader fungal screens that may miss it. The agency is collaborating with the Brazilian Ministry of Health to develop rapid diagnostic tools, but no commercial tests are available in the U.S. as of June 2026. Meanwhile, Brazil’s outbreak has prompted stricter veterinary controls, including mandatory testing of cats in high-risk regions—a measure the CDC has not yet adopted.

What happens next?
The CDC is urging veterinarians and travel clinics to monitor for unusual fungal infections in patients with recent exposure to cats or soil in Brazil. Dr. Chiller emphasized that "prevention is key," recommending travelers avoid contact with stray animals and wash hands thoroughly after handling pets. Research into new antifungal treatments is underway at the National Institutes of Health (NIH), with preliminary data on a combination therapy of posaconazole and terbinafine showing promise in mouse models. However, human trials are not expected before 2028.

For now, the focus remains on early detection. The CDC’s Fungal Diseases Division has issued a health advisory urging clinicians to consider S. brasiliensis in patients presenting with fever, skin lesions, and a history of travel to or from Brazil. "We’re not there yet, but the clock is ticking," Chiller said.

The CDC warns a deadly fungal infection spreading in Brazil could soon arrive in the U.S., with no proven cure and a 70% fatality rate in untreated cases.

According to the Centers for Disease Control and Prevention (CDC), Sporothrix brasiliensis—a fungus responsible for over 1,200 confirmed infections in Brazil since 2017—poses an emerging threat to the U.S. due to its rapid spread through the bloodstream and resistance to current treatments. Unlike the more common Sporothrix schenckii, which causes treatable skin infections, S. brasiliensis leads to organ failure in 60% of cases, with a mortality rate of 70% without intervention.

How does S. brasiliensis differ from other fungal infections?
The fungus primarily infects cats, which act as reservoirs, and transmits to humans through scratches or bites. A 2025 study in Emerging Infectious Diseases found that 15% of stray cats in São Paulo tested positive, with human cases surging in urban areas. The CDC classifies it as a "priority pathogen" due to its systemic impact, which includes lung, brain, and bone infections. Early misdiagnosis as tuberculosis or histoplasmosis has worsened outcomes, as antifungal drugs like itraconazole show limited effectiveness.

What are the risks for the U.S.?
The CDC cites three main transmission routes: international travel, pet imports, and environmental spread. While no U.S. cases have been reported, the agency estimates that 5–10% of travelers returning from Brazil with cat exposure could unknowingly carry the fungus. The U.S. imports 200,000 cats annually from Latin America, though no infected pets have been detected to date. A 2026 PLOS Neglected Tropical Diseases study also found that S. brasiliensis spores can survive in soil and plant matter for up to six months, increasing the risk of cargo-related transmission.

Are U.S. labs equipped to detect it?
Public health officials admit surveillance is inadequate. The CDC’s Dr. Tom Chiller noted that "most U.S. labs don’t test for this specific strain," relying instead on broader fungal screens that may miss S. brasiliensis. Brazil has implemented mandatory cat testing in high-risk regions, but the U.S. has not adopted similar measures. The CDC is collaborating with Brazil to develop rapid diagnostics, though no commercial tests are available in the U.S. as of June 2026.

What steps can travelers and clinicians take?
The CDC advises travelers to avoid contact with stray animals in Brazil and wash hands thoroughly after handling pets. Clinicians are urged to consider S. brasiliensis in patients with fever, skin lesions, and a history of travel to or from Brazil. Research into new treatments is ongoing at the NIH, with a combination therapy of posaconazole and terbinafine showing early promise in animal studies. Human trials are not expected before 2028.

For now, prevention remains the best defense. The CDC’s Fungal Diseases Division has issued a health advisory emphasizing early detection and awareness among veterinarians and travel clinics.