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Recent reports of outbreaks of the multidrug-resistant yeast Candida auris (C. auris) are worrying health officials and experts across the U.S.

As of January 26, with links to the same Seattle hospital tested positive for C. auris in the state's first known outbreak. Nationally, cases are higher than they've ever been.

Adding to concern is the risk that this microscopic fungus poses to already-sick patients, along with its unusual staying power on surfaces, and surveillance that relies on known cases.

What Is C. Auris and How Does It Spread?

C. auris is a highly transmissible yeast that can lead to infections, particularly in patients who already have serious medical conditions. Some infections may be mild, while blood infections are the most dangerous -- even deadly.

Those with like breathing tubes, feeding tubes, or catheters may be at higher risk for infection with C. auris, along with patients who have or care facility, as well as those who have been treated with antibiotics or antifungals in the past.

, "healthy people without these risk factors, including healthcare workers and family members, have a low risk for getting infected with C. auris."

Anthony Harris, MD, MPH, an infectious diseases physician at the University of Maryland School of Medicine in Baltimore, told 乌鸦传媒 that most multidrug-resistant organisms, "including C. auris, [occur] in people who have a lot of exposures to different types of healthcare facilities. It's people who've gotten a lot of antibiotics, and it's people who have comorbid conditions that predispose them," like immunosuppression.

However, the yeast can spread by attaching to the skin and other body sites, and can "colonize," meaning people may not become infected or ill but can still spread the disease through physical contact. It can also be spread through contact with contaminated surfaces or equipment.

How Widespread Is C. Auris?

The yeast was first detected in Japan in 2009, and wasn't identified in the U.S. until 2016. Many of the early C. auris cases were imported, but recent cases, including the first in , have been locally transmitted.

Documented C. auris cases have risen steadily , from 330 cases reported nationally in 2018 to 1,471 in 2021, which was a 95% jump from 2020. It has now been found in more than half of U.S. states. In the past 12 months, clinical cases have been highest in and near some of the most populous states: Florida, New York, and California.

Tracking C. auris can be a challenge for local health authorities, however, because it can be difficult to identify without , and screening for C. auris is not routinely conducted in many healthcare facilities, Harris said.

In an email, Meghan Lyman, MD, of the CDC's National Center for Emerging and Zoonotic Infectious Diseases, told 乌鸦传媒 that "all states do voluntarily report cases to the CDC. However, detection of colonization cases depends on screening practices, which [are] not uniform across the U.S."

Generally, screening for C. auris is recommended when patients or healthcare workers shared space or came into contact with a known case, or if a patient with multidrug-resistant bacteria recently received medical care outside the U.S.

In the Washington cases, the hospital had recently put in place a "proactive screening program" that swabbed all patients upon admittance for testing by the state health department's public health lab, which led to the early identification.

Why Are Public Health Authorities Concerned About C. Auris?

In addition to its surveillance challenges, C. auris is resistant to medicines normally used to treat other fungal infections. According to the CDC, a class of antifungals known as echinocandins can be used to treat the infection, but some C. auris strains are resistant to all antifungals.

The yeast can colonize human skin effectively, often in the armpits and groin, but also in the nostrils, fingertips, and palms, which makes it efficient in spreading over high-touch areas and even via contaminated gloves. Though methods like bathing patients with chlorhexidine gluconate solution, or using healthcare-grade disinfectants for surfaces, are commonly used, they are not completely effective. , no specific intervention "is known to reduce or eliminate C. auris colonization."

C. auris can also linger on surfaces in healthcare facilities for long stretches of time -- on floors, bed rails, bed sheets, door handles, oxygen masks, and sinks. In dry environments, it can survive on plastic for multiple weeks, and , "devices in contact with skin may be particularly prone to contamination by C. auris biofilms."

It can also be difficult to tell how much, or if, the fungal infection contributed to death in patients with ongoing medical problems and C. auris.

The best way to prevent outbreaks, Harris said, is to use proper hand hygiene and contact precautions including gowns, gloves, and . He also noted that funding programs like the CDC's allows institutions to do the kind of research that can identify new antifungals and prevention strategies. "It just seems amazing that post-COVID pandemic, that instead of investing more money in the CDC, we're investing less," Harris said.

Lyman noted that the "CDC encourages being proactive instead of reactive, since it is better to identify C. auris cases before there is spread."

"This may mean providing healthcare worker education, conducting screening, and assessing infection control compliance before a case is detected instead of waiting for a positive clinical specimen to prompt a response and finding that there has already been spread," she said.

Correction: A previous version of this story misidentified C. auris as a bacteria in one instance. It is a fungus.

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