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The fungus candida auris sits in a petri dish in black and white. the background is blue
C.auris (Image: Supplied)

ScienceMarch 28, 2023

What you need to know about the deadly fungus detected in New Zealand

The fungus candida auris sits in a petri dish in black and white. the background is blue
C.auris (Image: Supplied)

Candida auris is more likely to infect those who are already ill or immunocompromised and is fatal for 30-60% of those infected.

What is Candida auris?

Candida auris (also known as C. auris) is a type of fungus called a yeast. It was first identified in 2009 from the ear of a patient in Japan – hence “auris” which is Latin for ear. There are five main types (called clades) which are found in different regions of the world. More on this later. While some fungi really can turn their infected hosts into zombies, C. auris isn’t one of them.

So why is everyone worried?

Experts have been raising the alarm about C. auris for a few years now. One reason is because we have very few anti-fungal medicines and there are strains of C. auris that are resistant to all of them. Last year the WHO produced a list of the fungi that should be prioritised for more investment and research, including into new diagnostics and treatments. The 19 fungi on the list are categorised as either critical, high, or medium priority. C. auris is one of the four “critical” fungi.

The four critical fungi are listed on a red background: cryptococcus neoformans, candida auris, aspergillus fumigatus, candida albicans
The four critical fungi (Image: WHO)

It’s in New Zealand now. Should I be worried?

We know that C. auris can live on the skin of some people or inside them without them having any symptoms. That means it could have already been here before health officials detected it recently. This fungus is also often misidentified as other Candida species because it requires specific genetic tests to identify it. 

But given this is the first case to be reported in New Zealand and it’s in someone who was infected overseas, that suggests if C. auris is already here it isn’t widespread. People will be trying very hard to stop the fungus from contaminating whatever healthcare facility the infected person is in. That can be difficult as this fungus is generally very resistant to the commonly-used disinfectants. If they can’t get rid of it, then this may be the start of the fungus establishing itself in healthcare facilities here. 

Am I at risk? Who’s most likely to get it?

First, we need to distinguish between people just carrying the fungus in/on their bodies and those who it makes sick. On the US CDC website, it says that screening identified 5,754 people as having C. auris in the USA in 2022. It also says they had 2,377 clinical cases. These are the people who it made ill.

C. auris can infect people of any age, from preterm babies to the elderly. The people most likely to get sick are those who are critically ill or immunocompromised. They may have recently had surgery or a bone or organ transplant or have cancer. Hospital stays of longer than 10-15 days, and the need for breathing tubes, feeding tubes, and central venous catheters are also risk factors. Unsurprisingly, there has been a big increase in cases overseas since the Covid-19 pandemic began.

Outbreaks tend to happen in hospitals and long-term care facilities. As I said, the fungus is very hard to kill using commonly used disinfectants. This means it can contaminate surfaces and equipment and then spread to patients. It can also spread from person to person if someone is shedding the fungus. 

Does it kill people?

Yes, unfortunately it does. It looks like about 30–60% of people with a C. auris infection have died. This high number will be because it infects people who are already ill or immunocompromised, and because it’s difficult to diagnose. As I said earlier it’s also difficult to treat because some strains are resistant to what few antifungal drugs we do have. Most strains are sensitive to a class of drugs called echinocandins, but these aren’t available in many countries.

What are the symptoms?

C. auris can cause bloodstream, wound, and ear infections, among other things. The most common symptoms are fever, chills, sweats, and low blood pressure. These are all symptoms of bacterial infections too, so because it’s so rare, C. auris often isn’t diagnosed until someone doesn’t respond to antibiotics. Remember, antibiotics treat bacterial infections and not viral or fungal infections.

Can I do anything to lower the chance of getting it?

Not really. There isn’t a vaccine. The only thing we can do is ensure our hospitals aren’t under-funded and cleaned by people who are underpaid…

First Covid. Then monkeypox. Now a deadly fungus?

I know. It’s exhausting, isn’t it? It’s all sadly related. Here’s how C. auris fits in. 

What sets C. auris apart from the hundreds of other species of Candida is its ability to grow at higher temperatures. I said earlier that there are five main types (clades) of C. auris. They appear to have emerged simultaneously around the world as a cause of disease in people. The current leading theory is that climate change and global temperature changes are responsible. 

Researchers have proposed that in the wild, C. auris lives on dead plants in specialised environments like wetlands. Supporting this, Arora and colleagues recently isolated C. auris from coastal wetlands in India that few people ever visit. They found one strain that grew slowly at 37°C and 42°C and was sensitive to a range of antifungal drugs. But they also found 23 strains that grew well at these higher temperatures and were resistant to many antifungal drugs. The ability to grow at 37°C is important because that’s human body temperature. 

In other words, it looks like adaptation to increasing global temperatures has enabled strains of C. auris to leave the wetlands and cause disease in medically vulnerable people. Add in a lack of medicines that the WHO and others have been warning about for years, and a pandemic which has just made a whole bunch more people medically vulnerable, and we’ve created the perfect environment for that deadly fungus to thrive. 

Keep going!