When people hear the word “fungus,” they might think of bread mold, green furry spots on a peach, or mushrooms that pop up after it rains.
Some health officials believe that’s a potentially dangerous way to think.
Recent outbreaks of a new strain of fungi, Candida auris, at an English hospital and in other countries, are prompting international public health officials to take the fungal infection threat more seriously.
Until recently, such infections had not been a medical priority despite the fact some fungi can be killers.
Fungus among us
More than 1 million people die each year from fungal infections, more than from malaria or breast cancer.
“Most people know about mild fungal infections, but nobody's ever died from athlete's foot,” said Professor Neil Gow, Ph.D., director of research and commercialization at the College of Life Sciences, University of Aberdeen, in Scotland, in an interview with the BBC.
Gow said although such infections lead to so many deaths, there are no antifungal vaccines.
“We need to understand these different types of infection and how to deal with them,” he told the BBC.
Gow’s comments came after Public Health England (PHE) announced July 1 on its website that Candida auris, a drug-resistant yeast, had caused an outbreak of more than 40 cases in an adult critical care unit at a hospital in England.
PHE said sporadic cases of Candida auris have been identified throughout England since 2013. Candida auris was first reported and named in Japan in 2009. Since then, infections have been found in at least nine countries.
Dr. Tom Chiller, deputy chief of the Mycotic Diseases Branch of the U.S. Centers for Disease Control (CDC), told Healthline that Candida auris so far appears to be rare in the United States.
“But based on what is happening in other countries, including England, we are concerned about seeing it more in the United States,” he said.
Chiller’s research division is dedicated to preventing death and disability caused by fungal diseases.
“It is one of the only public health groups in the world devoted specifically to the prevention and control of fungal infections,” he said.
Research is under way at academic centers around the globe, he added, in the areas of resistance, drug development, and immune treatments.
Chad Rappleye, Ph.D., associate professor of microbiology in the Department of Microbial Infection and Immunity at The Ohio State University College of Medicine, said several factors contribute to the lack of attention to these infections.
“Most fungi either do not cause disease or are opportunistic pathogens that afflict the immuno-compromised, not the general population,” he told Healthline. “There are a few fungi that can cause disease in otherwise healthy individuals, but these are limited to certain geographic regions.”
“The public sees fungi as ‘gross’ molds and mildews that decay fruit and grow on damp basement walls, not as infectious agents” he added.
Another reason for the lack of public attention is fungal diseases in general are not contagious, or transmissible person-to-person.
“Candida is transmissible between people,” Rappleye said, “but most of us already have Candida on our skin and in our intestinal tract, and it causes no problems. It's a normal part of our flora.”
Candida becomes a threat in situations where people lack certain immune defenses, combined with defects in tissue barriers, Rappleye said.
Other fungi that cause life-threatening disease are acquired from the environment, usually through inhalation and not from another person.
Contrast this with the bacteria-borne disease tuberculosis, which is known to be transmitted person-to-person, Rappleye said, “and you see which is a ‘sexier’ story to tell the public.”
“A great example is the fact that more people die of Cryptococcus infections (a fungal agent) in Africa than from tuberculosis, but no one has heard of Cryptococcus,” Rappleye said. “When one person shows up in the United States with tuberculosis — a widespread infection, but only 5 to 10 percent of people ever develop the disease — the media goes frantic with calls for quarantines. But since life-threatening fungal infections are not generally contagious, they are never reported, even though they are widespread throughout the United States.”
A global issue
Which countries are currently affected?
In addition to the outbreak in England, Chiller said Candida auris infections have been reported in South Korea, India, South Africa, and Kuwait.
Although published reports are not available, Candida auris also has been identified in Colombia, Venezuela, and Pakistan.
It is likely that infections have occurred elsewhere but have not been identified, he added.
Fungal diseases are a public health issue because they occur frequently in hospitals, or can crop up in community outbreaks from fungi that live in particular regions.
Chiller said opportunistic infections like cryptococcosis and aspergillosis are particularly serious for people with weakened immune systems like cancer patients or people with HIV or AIDS. And the number of people with weakened immune systems is increasing, Chiller said.
“Hospital-associated infections like candidemia are a leading cause of bloodstream infections in the United States,” Chiller said.
Advancements and changes in healthcare practices can provide opportunities for new and drug-resistant fungi to emerge in healthcare settings, he noted.
“Community-acquired infections like Valley fever [reported in Southern California and Arizona] are caused by fungi that live in the environment in specific geographic areas,” Chiller said.
Weather and climate change may affect these types of fungi.
Why is this new infection emerging globally?
Chiller said it is not yet known why Candida auris has recently emerged in so many different locations. Molecular analysis suggests that the strains are emerging independently in many places and not spreading from region to region.
“It may be emerging because of changes in the use of antifungal drugs in people or animals, or antifungal chemicals in the environment,” he said.
What can people do to protect themselves?
“The best defense is to have an efficiently functioning immune system,” Rappleye said, “and decrease your exposure risk.”
This is difficult, as Candida is part of the normal human flora and most are already colonized. For Candida, increased "exposure" results from having a defect in one of the barriers of the body.
Skin, for example, is an “amazing barrier that prevents skin-localized Candida from invading deeper tissues, including the bloodstream, where it becomes life-threatening,” Rappleye said.
CDC guidelines to prevent the spread of Candida auris in healthcare settings include careful hand hygiene, contact precautions that involve wearing gowns and gloves, and thorough environmental cleaning of hospital rooms.