A deadly fungus that can infect cats and people is spreading

Microbiologists warn that a deadly fungus, Sporothrix brasiliensis, which infects cats and can spread to humans, is not yet confirmed in the United States but poses a significant threat of emergence.

Sporothrix brasiliensis, a fungus responsible for severe skin infections in cats and humans, has caused thousands of feline deaths and over 11,000 human cases in South America since the 1990s. Experts from the CDC and veterinary research warn that the fungus has spread to neighboring countries such as Paraguay, Chile, Argentina, and Uruguay. According to Shawn Lockhart, a senior CDC adviser, it is only a matter of time before the fungus reaches the U.S., especially in urban areas with large populations of stray or farm cats. The fungus can cause skin ulcers, respiratory issues, and systemic infections if untreated, with a high fatality rate in both cats and immunocompromised humans. The infection spreads through scratches, bites, grooming, and sneezing, with the fungus capable of surviving on surfaces for weeks, increasing the risk of transmission.

Current evidence indicates the fungus is primarily confined to South America, with no confirmed cases in North America. However, health officials emphasize the risk of importation via infected animals or travelers. The unique ability of S. brasiliensis to spread in its yeast form, unlike other fungi, raises concerns about its potential to establish in new environments.

Why the Spread of S. brasiliensis Matters for Public Health

The emergence of Sporothrix brasiliensis outside South America could pose a serious zoonotic threat, especially in urban centers with large cat populations. Its ability to infect both animals and humans, combined with increasing global travel and animal movement, raises concerns about potential outbreaks in the United States and beyond. The high fatality rate in untreated cases and the fungus’s resilience on surfaces make it a public health concern that requires monitoring and preparedness.

Background on S. brasiliensis and Its Regional Impact

Sporothrix brasiliensis is a fungus first identified in Brazil in the 1990s, where it caused a significant outbreak among cats, leading to widespread infections in humans. Unlike other fungi, it can spread directly from cats to humans through scratches, bites, or sneezing. The fungus is a dimorphic organism, existing as mold in soil and as yeast in hosts, which facilitates its infectiousness. Its spread has been contained mostly within South America, but recent reports of cases in neighboring countries highlight its expanding geographic range. Experts have warned for years about the potential for this fungus to spread globally, especially given the high number of stray cats and international travel.

“It’s just a matter of time before Sporothrix brasiliensis reaches the United States, especially in urban areas with large populations of stray cats.”

— Shawn Lockhart, CDC senior adviser

Unconfirmed Cases and Geographic Spread Risks

There are no confirmed cases of Sporothrix brasiliensis in the United States or other non-South American countries. It remains unclear when or if the fungus will establish itself outside South America, and how effectively it can be contained if introduced. Surveillance efforts are ongoing, but the full extent of its potential spread is still unknown.

Monitoring, Preparedness, and Preventive Measures

Health authorities are increasing surveillance for imported cases, especially in major U.S. cities with large stray cat populations. Researchers are also studying the fungus’s survivability and transmission pathways to develop better control strategies. Travelers and pet owners are advised to be cautious, especially when handling animals from South America. The next steps include enhanced diagnostic capabilities, public awareness campaigns, and international cooperation to prevent or contain potential outbreaks.

Key Questions

Can humans catch Sporothrix brasiliensis from cats?

Yes, humans can become infected through scratches, bites, or contact with infected cats’ secretions or sneezing. The fungus can cause skin ulcers and, in severe cases, systemic illness.

Is there a treatment for the infection?

Antifungal medications are effective if administered early. However, untreated infections can be fatal, especially in immunocompromised individuals.

How can the fungus be prevented from spreading?

Preventive measures include avoiding contact with stray or infected cats, practicing good hygiene, and ensuring pets are checked and treated if exposed. Surveillance and rapid response are key to containment.

Are there signs to look for in infected cats?

Infected cats typically develop skin ulcers, nodules, and swollen lymph glands. They may also show signs of respiratory distress if the infection spreads internally.

Source: Hacker News