A rare fungus is spreading in the United States! Will it cause a global spread?

The Centers for Disease Control and Prevention (CDC) issued a warning in the Annals of Internal Medicine this week that a rare and sometimes deadly fungus is spreading rapidly in medical institutions in many states in the United States, and the number of related cases has increased dramatically. The CDC said that this fungal infection called Candida auris is also resistant to multiple antifungal drugs and "poses a serious threat to global health."

In a report published on March 22, the website of Newsweek magazine analyzed the main reasons for the rampant Candida auris infection in the United States: hospital environments make it easy to spread, and there is a lack of efficient detection measures. In addition, climate change has also led to the accelerated spread of various fungi, including Candida auris, which urgently needs to be paid attention to.

Diagram of the structure of Candida auris. Image source: Newsweek website

Candida auris is spreading rapidly in the U.S.

The CDC said that Candida auris is spreading rapidly across the United States, with 17 states reporting their first cases of Candida auris infection between 2019 and 2021. Between 2018 and 2019, cases of Candida auris infection in the United States increased by 44%; between 2020 and 2021, cases increased by 95%: from 756 cases in 2020 to 1,471 cases in 2021. At least 2,377 cases of infection were reported across the United States in 2022.

Candida auris is a type of yeast that usually causes no symptoms, but can cause symptoms such as bloodstream infections, wound infections, and ear infections in people with weakened immune systems.

People at greatest risk include those who are immunocompromised, have had recent surgery, have certain forms of diabetes or have recently used broad-spectrum antibiotics and antifungal medications. Candida auris infections most often affect people in hospitals, killing about a quarter of those infected.

Rodney Rod, professor of clinical laboratory science at Texas State University, said that cases of Candida auris infection have been reported in more than 30 countries, including the United States. These fungi often appear in blood, urine, sputum, ear secretions, cerebrospinal fluid and soft tissues, and may appear in people of all ages.

He further pointed out that CDC data show that the mortality rate of Candida auris infection in patients with other serious diseases in the United States is between 30% and 60%. In a 2018 review of the global spread of all cases of Candida auris to date, the mortality rate of Candida auris infection in seriously ill patients was estimated to be 30% to 70%.

Hospital environment makes it easy for transmission

Newsweek's analysis pointed out that the surge in cases in the United States may be due to the easy spread of the pathogen in hospital environments and the difficulty in detecting Candida auris infections.

Daniel Henke, a fungus expert and lecturer in microbial ecology at the University of Bath, said that Candida auris is shed in hospital environments and can persist on patients and medical equipment for a long time. He believes that the emergence of Candida auris in the UK is related to reusable underarm thermometers.

Rohde noted that environmental surfaces and medical devices are common ways for fungal infections to spread, especially to people with weakened immune systems. He explained that one of the key mechanisms that causes this to happen is the formation of biofilms. Overall, poor infection prevention and control (IPC) measures in healthcare facilities may be one of the "culprits."

The CDC's main concern is that Candida auris often appears in medical settings with hospitalized patients and is often mistaken for another disease because it is difficult to detect. In addition, the fungus is often resistant to antifungal drugs, and the results showed that almost all samples tested for Candida auris were resistant to at least one class of antifungal drugs. Rodzo testified that in 2021, the number of cases of resistance to echinocandins (one of the most commonly used antifungal drugs to treat Candida auris infections) increased threefold.

In addition to the surge in confirmed cases in the United States, more than 30 other countries have also reported cases of Candida auris infection. However, Henke pointed out that it is too early to say that Candida auris will spread widely around the world.

So, how to prevent and control Candida auris infection?

Rod suggested that everyone should pay attention to hand hygiene, wash their hands with soap and warm water or alcohol-based hand sanitizer, and healthcare professionals should also wear appropriate personal protective equipment, such as gloves. Most importantly, people urgently need powerful diagnostic methods to accurately identify fungal infections in medical and public health laboratories.

Henke said that preventing transmission within and between hospitals may require a variety of measures. Perhaps the most important is to really improve diagnostic and surveillance methods to alert people to potential epidemics as early as possible, because once an epidemic is established, it is often too late and difficult to manage effectively.

Climate change accelerates fungus spread

Researchers have also pointed to climate change as a factor in the accelerated spread of fungal infections, with some experts pointing out that climate change could further increase the widespread spread of fungi in the coming years.

Lord said some researchers estimate that climate change and other similar factors (encroachment on nonhuman habitats) could lead to an increase in outbreaks worldwide. Candida auris is an urgent threat in the United States and is listed as a global priority pathogen on the World Health Organization's list of fungal priority pathogens.

But C. auris isn't the only fungus that could become more widespread due to climate change. A fungal skin infection called chytridiomycosis is devastating frogs around the world, and it may spread faster and more widely due to climate change. And valley fever, a fungal infection usually found only in southwestern states, has spread across the country, a shift scientists believe is due to changing weather patterns caused by climate change.

Source: Science and Technology Daily

Reporter: Liu Xia