Last June, the US Centres for Disease Control and Prevention (CDC) warned health clinics about the emergence of a new multidrug-resistant yeast strain called Candida auris.

Just a few months later, the first seven cases of C. auris infection in the US were reported. Now it's clear that the fungus has started a march through US hospitals, and healthcare officials are concerned.

C. auris is a recently discovered fungus species that can cause severe infections in humans. It was first described in 2009, discovered in a Japanese patient with a nasty ear infection.

Since then, it has been detected in nine countries on four continents, and data shows it has "high potential to cause outbreaks in healthcare facilities".

According to the latest CDC report, 77 C. auris clinical cases have now been identified across seven US states, with additional 45 cases found via screening of people who were in contact with the patients.

Of the clinical cases, nearly 70 percent were identified in the New York City metropolitan area, with the next highest number in New Jersey.

CDC

Genetic analysis of the isolated strains in comparison to samples from elsewhere in the world shows that C. auris likely entered the US through several distinct routes, and then spread locally.

"There are four different families or groups that emerged simultaneously ... and independently," CDC officer Paige Armstrong told Susan Scutti at CNN.

Candida fungi are the most common cause of yeast infection in the world, and nearly everyone has a few of these living on their skin. When they turn on you and start a colony, in most cases a quick round of antifungal medicine is all it takes to clear up the infection.

But C. auris appears to be much worse than its garden-variety cousins, because it is often multidrug-resistant, just like superbugs. It's also harder to identify, which increases risk an infection won't be treated properly.

"This is a fungus that's acting a lot like some super bacteria that we've seen previously," said Armstrong.

For now, the new Candida species is spreading mainly through healthcare facilities, where it affects people with pre-existing medical conditions.

"It seems to affect the sickest of the sick patients, particularly those in hospitals and nursing homes with other medical problems," CDC officer and lead author of the new report, Sharon Tsay, told CNN.

The most dangerous type of fungal infection is invasive candidiasis, when the yeast manages to get into the bloodstream - and that's exactly what C. auris does best.

But it's also been found in wound and ear infections, and has been isolated from the respiratory tract, urine, bile fluid and even bone, leading doctors to wonder why it's so good at sticking around, and what other kinds of infections it might cause.

"The fact that it has been found in other sites may also reflect its ability to persist on a patient's body and be spread in the environment around them - one of (the) reasons that C. auris is causing outbreaks," said Tsay.

The fungus has been associated with several deaths, but so far it's hard to tell what mortality rate it has, because patients often already have another disease before the yeast invades.

Different strains have been found to be resistant to all three main classes of antifungal drugs, but none have proven to be completely resistant, and most strains are susceptible to a relatively new drug class, echinocandins.

For now, CDC is monitoring the situation and has issued detection and treatment recommendations for healthcare facilities that suspect they might have a patient with a C. auris infection.

There's hope that with such early warning and increased vigilance, doctors may be able to prevent the worst outbreaks. And unless you're in a hospital in New York, there's probably not much to worry about just yet.

"It is important for New Yorkers to understand C. auris poses no risk to the general public," New York State Health Commissioner Howard Zucker said in a press statement.

"[W]e're taking aggressive actions to contain its spread in hospitals and nursing homes."

The report is available online at Morbidity and Mortality Weekly Report. CDC also has answers to common questions about C. auris available here.