In recent years, fungi have earned a spot on the world’s watch list of deadly pathogens. In 2022, the World Health Organization named its first-ever list of priority fungal threats, placing the yeast Candidozyma auris, formerly known as Candida auris, in the most serious category alongside just three other pathogens. It’s dangerous less for its virulence than for how hard it is to kill: it resists many antifungal drugs, survives for weeks on surfaces and spreads easily in healthcare settings.
First identified in 2009 in Tokyo, C. auris has since spread worldwide, posing a particular risk to nursing home residents and long-term care patients. The first United States case was reported in 2016; by 2024, the country was seeing over 6,300 new cases a year, according to the U.S. Centers for Disease Control and Prevention. Florida has consistently ranked among the top five states for reported cases since tracking began.
When a cluster of C. auris cases appeared at University of Florida Health in 2023, the health system’s infection control program partnered with UF Emerging Pathogens Institute researchers to trace the origins of the infections and how resistance was moving through them. Pairing frontline infection control with academic genomic research allowed the outbreak to be reconstructed in detail. The resulting study was selected as Editor’s Choice for Oxford Academic’s Open Forum Infectious Diseases, and its findings have since been built directly into UF Health’s ongoing surveillance protocols.
Tracing the source
C. auris has six major genetic clades. In 2023, researchers — including EPI members Glenn Morris, Jr., M.D., Massimiliano Tagliamonte, Ph.D., Tamara Revazishvili, Ph.D., Nicole Iovine, M.D., Ph.D., John Lednicky, Ph.D., and Marco Salemi, Ph.D., among others — studied samples from 36 patients collected over 11 months and found that the strains circulating in their hospital system belonged to two of the six: one linked to European and Middle Eastern strains, and another specific to Florida.
The spread pattern proved more complex than the single-source outbreaks typically seen with this fungus. The European-linked strains appeared to come from a single source. Patients infected with this group had little contact with the outside world, suggesting the fungus entered the hospital once and then spread internally, likely originating overseas. The Florida strains, however, showed up in several unrelated clusters, suggesting the fungus was introduced multiple times, most likely carried in by patients transferring from other healthcare facilities.
Containing the spread
C. auris mainly colonizes the skin, particularly in warm, moist areas like armpits and skin folds, and patients carrying a high fungal load are more likely to spread it to their surroundings. To counter this, the hospital screens high-risk patients — those who have spent more than five days in a long-term care or rehabilitation facility — at admission, even without symptoms. The room is put on contact precautions, meaning gowns, gloves, dedicated equipment and strict hand hygiene are required. Samples are then collected and contact precautions stay in place until the lab results come back.
A positive result without infection means the patient is “colonized.” Yeast is present but hasn’t entered the bloodstream. These patients remain on contact precautions and under close monitoring but are not treated, since antifungals must be used sparingly to avoid accelerating the resistance the study itself was tracking.
Distinguishing a single internal spread event from multiple independent introductions directly shapes how a healthcare facility responds. One calls for tightening internal infection control, the other for scrutinizing transfer screening. In this case, both were implemented.
The study also found that people can carry C. auris for extended periods without symptoms, and that in five patients, silent colonization progressed to bloodstream infection. Some patients tested negative and later tested positive, showing that the fungus can persist undetected even after a single culture-based test. The research team recommended genetic sequencing over culturing as a more reliable diagnostic method. Today, UF Health has adopted using PCR testing, cutting screening turnaround from three days to under 24 hours, alongside C. auris-targeted disinfectants and ultraviolet room disinfection after discharge.
Together, these findings show why sustained surveillance matters: C. auris can spread quietly through multiple routes at once, and left unchecked, poses a serious risk to vulnerable patients. By identifying where and how outbreaks begin, healthcare systems can sharpen the tools protecting those most at risk.
Written by: Sydney Burge