Candida auris: What is the deadly fungus sweeping through US hospitals?


Although it was only identified about 15 years ago, the drug-resistant fungus Candida auris (C. auris) is already one of the most dreaded medical microbes in the world.

The yeast-like fungus has the ability to enter the body and cause damage to various internal systems, the nervous system, and the bloodstream. According to the World Health Organization (WHO), patients with an invasive infection have a mortality rate that varies from 30% to 53%.

The fact that the fungus has shown to be immune to the most popular classes of antifungal medications is more concerning. James Gallagher, a health reporter for the BBC, claims that some strains are resistant to every medication we currently have.

The US Centers for Disease Control and Prevention (CDC) reports that epidemics have occurred in more than 30 nations.

Candida reported cases map

The CDC said new data showed the fungus has “spread at an alarming rate in US healthcare facilities” in 2020 and 2021. Clinical cases in the country trebled – from 476 in 2019 to 1,471 in 2021.

Also, a 2019 study by an international team of researchers suggested that rising temperatures linked to climate change may have played a role in the rising number of Candida auris infections.

Here is everything you need to know about this deadly superbug.

What is Candida auris?

Candida auris (C. auris) is a yeast, a family of fungus which contains species pretty helpful to humans in activities such as bread-making and beer-brewing, but which also features species that cause infections in humans.

A picture of a slice of breadIMAGE SOURCE,GETTY IMAGES
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Some yeast fungi species have been pretty useful to humans

One example is the very common Candida albicans, which causes thrush but also may trigger more severe infections.

C. auris was first discovered in the ear canal of a patient at the Tokyo Metropolitan Geriatric Hospital in 2009, which inspired its name (auris is Latin for ear).

Most of the time, Candida yeasts live on our skin without causing problems, but they can cause infections if we are unwell or they get into the wrong place, like the bloodstream or the lungs.

What sort of illness does it cause?

C. auris most frequently causes bloodstream infections, but it can also affect the respiratory system, the central nervous system and internal organs, as well as the skin.

These infections are usually quite serious.

The fungus is often resistant to the usual drugs, which makes infections difficult to treat.

“The biggest problem with this fungus is its resistance to the drugs we have,” said Dr Tina Joshi, associate professor in Molecular Biology at the University of Plymouth, in the UK.

“But another issue is that identifying a C. auris infection is quite difficult and it can easily be mistaken for other fungi, leading to the wrong treatment.”

Pills being held near Petri dishesIMAGE SOURCE,GETTY IMAGES
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C. auris is often resistant to the most common anti-fugal drugs, which makes infections difficult to treat

This means that the patient might be ill for longer, or get worse before accessing the appropriate treatment.

How does it spread?

Transmission is mainly through contaminated surfaces in hospitals. It sticks to intravenous lines and blood pressure cuffs. It’s really hard to clean off, according to Dr Neil Stone, leading fungal expert at the Hospital for Tropical Diseases, University College London.

The solution is often to close off entire wards.

“It is the most worrying fungi and we ignore it at our peril,” Dr Stone said.

“It could shut down entire healthcare systems.”

In a statement issued on 20 March, the CDC said new data showed that the fungus has “spread at an alarming rate” in the US.

Should I be worried about getting an infection?

It is unlikely that you will pick up a C. auris infection going about your daily life.

However, the risk is higher if you are in a hospital for a long time or if you are in a nursing home, and patients who are in intensive care are much more likely to get a C. auris infection, according to the CDC.

A woman's hand with an intravenous lineIMAGE SOURCE,GETTY IMAGES
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The fungus sticks to all kinds of surfaces in hospitals, including intravenous lines

The risk of picking up an infection is also higher if you have been on antibiotics a lot, because the drugs also destroy good bacteria that can stop C. auris getting in.

Why is C. auris resistant to the usual drugs?

Resistance to the common antifungal drugs, like fluconazole, has been seen in the majority of C. auris strains.

This means that these drugs do not work on C. auris. Because of this, less common antifungal drugs have been used to treat infections, but C. auris has now developed resistance to these, too.

DNA evidence shows that the antifungal resistance genes in C. auris are very similar to those found in the very common C. albicans.

This suggests that the resistance genes may have passed from one species to the other.

How can climate change be responsible for the high numbers of infections?

A 2019 study, published by the journal mBio from the American Society for Microbiology, suggested that the reason C. auris infections have become so common may be because this species has been forced to live at higher temperatures because of climate change.

Most fungi prefer the cooler temperatures found in soil. But, as global temperatures have risen, C. auris has been forced to adapt to higher temperatures.

A hospital room in the US being cleaned with UV lightsIMAGE SOURCE,GETTY IMAGES
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More infection prevention efforts are needed in the battle against C. auris, experts say

This may have made it easier for the fungus to thrive in the human body, which is warm at 36C to 37C.

What can be done to control the number of infections?

A better understanding of who is most at risk of contracting a C. auris infection is the first step towards reducing the number of infections.

“We are behind the curve in what concerns the study of fungi,” Dr Joshi said.

“I am not surprised at all we are now having to catch-up with it.”

Healthcare professionals need to know that people who spend long periods of time in hospitals or nursing homes or those who have a weakened immune system are at higher risk.

Not all hospitals identify C. auris in the same way. They are sometimes mistaken for other fungal infections, like thrush, and the wrong treatment is given.

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C. auris is related to the more commonly found fungus Candida albicans

Improving diagnosis will help to identify patients with C. auris earlier, which will mean that the right treatment is given – preventing the spread of infection to other patients.

But above all, infection prevention efforts need to be improved, said Dr Joshi.

“The main measure is infection prevention and control, because we have already seen how difficult it is to tackle what it does to patients.”

“Hospitals need to be on top of disinfecting and cleaning.”

Is this the only nasty fungus around?

Not quite. In its first-ever list of fungal “priority pathogens”, published last October, the WHO named no less than 19 fungi that represent a great threat to public health.

C. auris was one of four fungi to appear in the “critical priority” group, being described by the WHO as “intrinsically resistant to most available antifungal medicines”.