Fully Resistant Superbug Fungus Spreads Between People in the U.S. for the First Time

Fully Resistant Superbug Fungus Spreads Between People in the U.S. for the First Time
Photo: Mario Tama, Getty Images

A dangerous, drug-resistant fungal infection seems to have accomplished a new scary feat in the U.S. On Friday, officials with the Centres for Disease Control and Prevention reported two unrelated outbreaks of Candida auris that happened earlier this year. The outbreaks were found in long-term care facilities and hospitals and featured fully and highly resistant strains that were likely transmitted from person to person, making them the first such reported cases in the country.

C. auris is an emerging superbug threat first discovered in 2009. Though the fungus can colonise people without making them sick, it has a high lethality when it becomes a widespread infection that invades different parts of the body, including the blood (upward of 30% mortality rate). This risk is especially serious for people with already weakened immune systems, like those visiting hospitals or living in long-term care facilities. It’s unnerved doctors and public health experts because of its ability to quickly evolve resistance to the few antifungals available to treat it. What’s worse, the yeast can quickly spread in environments where it becomes established, and it’s very hard to fully remove from surfaces and objects.

Any appearance of C. auris is enough to send alarm bells ringing. But these latest cases, detailed this week in the CDC’s Morbidity and Mortality Weekly Report, add a new worrying wrinkle. According to the report, there were two clusters of C. auris documented between January and April in Texas and Washington D.C. Though these clusters didn’t seem to share a common origin, they were nonetheless eerily similar.

Both outbreaks involved patients in hospitals or who were receiving long-term care. And in some of the cases, patients had strains of C. auris that were either resistant to all available antifungals (known as pan-resistance) or to the most important class of antifungals used for severe infections, called echinocandins. Of the 101 cases of C. auris (including both acutely sick and colonised patients) found in D.C., three were pan-resistant; of the 22 cases documented in Texas, two had pan-resistant strains and five had strains resistant to echinocandins and another drug class. Overall, 30% of patients in these outbreaks died within 30 days, though it’s not known exactly how many deaths C. auris may have contributed to, since many of the patients were already ill.

Pan-resistant cases of C. auris are unfortunately not unheard of, even in the U.S. But past cases here seemed to be isolated incidents where earlier treatment with an antifungal had goaded the fungus into becoming more resistant. In both outbreaks, though, the CDC investigators found that all of the people who contracted a highly resistant strain had no exposure to these drugs, indicating that it had spread beyond the original (and unknown) source to others. As far as the authors can tell, these are the first known cases of person-to-person transmission involving these pan-resistant strains.

“Surveillance, public health reporting, and infection control measures are critical to containing further spread,” the authors wrote. For doctors, they add, it might be worthwhile to test patients with these infections early on for possible resistance, especially in cases where the initial treatment fails. More work is also needed to figure out how to treat these pan-resistant infections.

If there is a silver lining here, it’s that C. auris remains a relatively rare danger in the U.S., even in potential hotspots like hospitals. But it and other superbugs are poised to become an ever larger public health threat in the years to come, as the pipeline of new antimicrobials that could treat these infections has slowed to a trickle (this may be an even bigger problem for fungal infections, since fewer antifungals are available to begin with compared to antibiotics). Without major changes, it may only take several decades before drug-resistant infections overtake cancer as a leading cause of death worldwide.

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