More than 200 patients in England have been infected or contaminated with a drug-resistant fungus first found in Japan, health officials have confirmed.
Hospitals are on the lookout for further cases and are putting in place measures to help control any further spread of the fungus, Candida auris .
Public Health England says in some cases patients will have no symptoms, but the infection can cause serious bloodstream and wound infections.
So far, no UK patient has died from it.
The first UK case emerged in 2013. Since then, infection rates have been going up - although it remains rare.
Candida auris is proving hard to stop because it has developed some resistance to the drug doctors normally use against it.
As of July, 20 separate NHS trusts and independent hospitals in the UK had detected Candida auris .
More than 35 other hospitals have had patients known to be colonised with Candida auris transferred to them.
Three hospitals have seen large outbreaks that have been difficult to control, despite intensive infection prevention and control measures.
These outbreaks have now been declared over, however, Public Health England says.
Dr Colin Brown, from Public Health England's national infection service, said most of the UK cases had been detected by screening, rather than investigations for patients with symptoms. But 27 patients have developed bloodstream infections.
"Our enhanced surveillance shows a low risk to patients in healthcare settings. Most cases detected have not shown symptoms or developed an infection as a result of the fungus.
"NHS hospitals that have experienced outbreaks of Candida auris have not found it to be the cause of death in any patients."
He said PHE had updated its infection-control guidance for hospitals and nursing homes on managing outbreaks of Candida auris , together with a leaflet for patients who may have the fungal infection.
What is Candida auris ?
It belongs to a family of fungi or yeasts that live on the skin and inside the human body.
A more common "cousin" in this family is Candida albicans , which causes the yeast infection thrush.
Candida auris was first identified in 2009 in a patient from Japan.
Hospital outbreaks have since been reported in the United States, India, Pakistan, Venezuela, Colombia, Israel, Oman, South Africa and Spain, as well as the UK.
Is it dangerous?
Some people can carry the infection without having any symptoms or being unwell.
Patients in hospital who catch it may become sick, although infections are still usually minor.
Candida auris can cause more serious bloodstream and wound infections, however.
Nursing staff can take swabs from different parts of a patient's body to check if Candida auris is present.
How is it spread?
That is still being investigated, but experts think it is spread by contact from person to person, on people's hands, clothing or on bits of medical equipment.
Contamination is quick - several hospitals have reported it takes as little as four hours from initial exposure.
What stops it?
Spread can be limited by good hygiene - keeping hands clean by frequent hand washing and using alcohol gel.
If a patient in hospital is found to be infected, their visitors may be asked to wear a gown, plastic aprons and gloves.
Antifungal medicines can treat the infection, despite the strain of Candida auris in the UK having some resistance to some of these drugs.
A biosafety Investigation Unit at Porton Down, the government's military research base, is testing a variety of disinfectants and antiseptics to see if they can kill the infection.