Infectious disease threats to human health are plentiful, and many of these pathogens are becoming more and more evasive to modern medical interventions. That’s why the serious outbreak potential of fungal infections is receiving increased attention in recent months. In fact, later his month, the CDC is organizing the first Fungal Disease Awareness Week to highlight the importance of recognizing serious fungal diseases early in the course of a patient’s illness to provide life-saving treatment. Of particular concern is Candida auris, a newly emerging fungus that includes strains resistant to all classes of antifungals.
Candida auris was first isolated in 2009 from a hospital patient in Japan, and there have since been several reports of nosocomial fungemia around the globe, including South Korea, Spain, and Kuwait (among others), as well as a large nosocomial outbreak in the United Kingdom. In June 2016, the CDC released a clinical alert warning US healthcare facilities to be on the lookout for C. auris, an emerging multidrug-resistant (MDR) yeast that was causing “invasive healthcare-associated infections with high mortality” in international healthcare facilities. At that time, there had been only one case of C. auris in the US in a patient who had recently been transferred from a hospital in the Middle East; however, as of July 2017—barely a year after the clinical alert—there have been 98 total cases in the US, six of which actually occurred before the alert but were retroactively identified.
The emergence of C. auris is worrisome for several reasons. First, genetic sequence analysis of isolates from 4 different global regions “suggests near-simultaneous emergence of C. auris in 4 locations rather than recent spread from a single source.” This, much like the emergence of antibiotic resistance, could be due to the increasing use of antifungals and the subsequent selection pressure it places on the fungi to survive. As a result of these selection pressures, some isolates have developed resistance to all 3 major antifungal classes, severely limiting treatment options.
Additionally, C. auris is difficult to diagnose and is often misidentified as other yeasts. This could not only delay treatment, but also delay the implementation of proper infection control measures needed to inhibit transmission. This is particularly important in hospital settings, where those most vulnerable to infection—including people with invasive medical devices (e.g., urinary catheters, central line catheters) and the immunocompromised—are at increased risk for infection.
Lastly, and perhaps most worrisome, C. auris infection has a case fatality rate of 30-60% (based on information from a limited number of patients). Many of these patients had comorbidities that increased their risk of serious disease and death, but considering the numerous reports of nosocomial C. auris infection, those at highest risk for death are also those at the highest risk for infection.
How significant is the danger? Recently, former CDC Acting Director Dr. Anne Schuchat said that C. auris poses a “catastrophic threat” to the public. Other health experts agree. In a commentary piece for the Johns Hopkins Center for Health Security’s special feature on Global Catastrophic Biological Risks (Health Security, July/August 2017), Dr. Arturo Casadevall wrote, “As we prepare to confront global catastrophic biorisks, we must consider the possibility that new threats from the fungal kingdom will be the future wars.” Dr. Casadevall is Chair of the Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health.
While the ability to treat complex and life-threatening illnesses and injuries has dramatically improved over time, the use of aggressive immunosuppressive therapies and invasive medical devices is also likely contributing to the emergence of deadly fungal infections such as C. auris. It’s an unfortunate paradox, but one we cannot afford to place in the “too hard to deal with” bin. Given their high mortality rate, increasing resistance to antifungals, propensity for spreading in hospitals, and difficult diagnoses, fungal infections like C. auris must not be underestimated in their ability to cause disease and death. We must give appropriate weight to potentially lethal fungi in our strategies to improve the availability of effective medical countermeasures and surveillance systems that detect and manage infectious disease outbreaks.
Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly in near-real time to allow others to learn from these experiences in order to improve global outbreak response capabilities.
Photo courtesy of CDC/Shawn Lockhart