A fungal superbug called Candida auris is spreading rapidly through hospitals and nursing homes in the US. The first case was identified in 2016. Since then, it has spread to half the country’s 50 states. And, according to a new report, infections tripled between 2019 and 2021. This is hugely concerning because Candida auris is resistant to many drugs, making this fungal infection one of the hardest to treat.
Candida auris is a yeast-type fungus that is the first to have multiple international health alerts associated with it. It has been found in over 30 countries, including the UK, since it was first identified in Japan in 2009.
It is related to other types of yeast that can cause infections, like Candida albicans which causes thrush. However, Candida auris is very different to these other fungi and in some ways, highly unusual.
First, it can grow, or “colonise”, human skin. Unlike many other Candida species that like to grow in our guts as part of the microbiome, Candida auris does not grow in this environment and seems to prefer the skin. This means that people who are colonised with Candida auris can shed lots of yeast from their skin, and this contaminates bed clothes and surfaces with the fungus. This can lead to outbreaks.
It is unusual for a fungal infection to spread from person to person, but that seems to be how Candida auris infections spread. Outbreaks can happen with this fungus, especially in intensive care units (ICU) and nursing homes where people are at a higher risk for getting fungal infections generally.
The fungus can live on surfaces for several weeks, and getting rid of it can be difficult. Enhanced cleaning and hand washing is needed to try and limit the spread of the fungus and exposure to patients who get ill from it.
Most people who are colonised with Candida auris will not get ill from it, or even know it is there. It causes infections when it gets into surgical wounds or the blood from an intravenous line. Once it gets into the body, it can infect organs and the blood causing a very serious and potentially fatal disease.
The mortality rate for people infected (as opposed to colonised) with the fungus is between 30 and 60%. But a precise mortality rate can be hard to pin down as people who are infected are often critically ill with other conditions.
Diagnosing an infection can be difficult as there can be a wide range of symptoms including fever, chills, headaches and nausea. It is for this reason that we need to keep a close eye on Candida auris as it can easily be confused with other conditions.
In the last few years, new tests to help identify this fungus accurately have been developed.
The first Candida auris infection was reported in the UK in 2013. However, there may have been other cases before this – there is evidence that some early cases were misidentified as unrelated yeasts.
The UK has so far managed to stop any major outbreaks, and most cases have been limited in their spread.
Most patients who have become ill from Candida auris in the UK had recently travelled to parts of the world where the fungus is more common or has been circulating for longer.
Spurred by COVID
Rising numbers of Candida auris infections are thought to be partially linked to the COVID pandemic. People who become very ill from COVID may need mechanical ventilation and long stays in the ICU, which are both risk factors for Candida auris colonisation and infection.
It will take some time to figure out exactly how the pandemic has affected rates and numbers of fungal infections around the world, but these are important questions to answer to help predict how Candida auris cases might fluctuate in the future.
As for most life-threatening fungal infections, treatment is difficult and limited. We have only a handful of antifungal drugs to fight these infections, so when a species is resistant to one or more of these drugs, the options for treatment are extremely limited. Some Candida auris infections are resistant to all three types of antifungal drug.
Healthcare professionals must remain vigilant to this drug-resistant fungus. Without close monitoring and enhanced awareness of this infection, we could see more outbreaks and serious disease associated with Candida auris in the future.
Rebecca A. Drummond receives funding from the Medical Research Council.