Epidemiology

Systemic candidiasis is generally a disease related to modern medical therapy. As such it is primarily seen in patients who are or have been recently hospitalized and have medical devices present, such as intravascular catheters, or patients who have immune compromise. Injection drug use is an emerging risk factor for community-onset candidemia.[2]​ Candidemia is a growing global concern in terms of both burden of disease and antimicrobial resistance. There are an estimated 25,000 cases of candidemia in the US each year, and it is one of the most common nosocomial bloodstream infections in the US and Europe.[3]​​[4]​​​​​​​[5][6]​​​​​ However, candidemia only represents a portion of systemic candidiasis burden. Estimates for the years 2019-2021 suggest that about 1,565,000 people globally develop Candida bloodstream infection or invasive candidiasis each year, with 995,000 deaths, resulting in a crude mortality rate of 63.6%.[7]​ Candida species are highlighted as an urgent threat in the US Center for Disease Control and Prevention's 2021-2022 Antibiotic Resistance Threats in the US, and critical and high priority groups in the World Health Organization's 2022 fungal priority pathogens list.[8]​​[9]

​Nearly all systemic candidiasis is caused by 5 species: Candida albicans, C glabrata, C parapsilosis, C krusei and C tropicalis. C albicans is the most common species causing infection. However, its relative contribution to cases of invasive candidiasis is declining, and nonalbicans species now account for more than 50% of diagnoses of candidemia and invasive candidiasis.​​[3]​​[10]

There is wide global variation in the predominance of particular species, with C tropicalis common in South America and Southeast Asia, and C parapsilosis common in Europe.[11][12][13]​​​​​ In addition to the changing epidemiology of Candida species, decreased mortality has also been observed.[14] The increase in nonalbicans species is particularly concerning as these species are more likely to be resistant to fluconazole, the mainstay of systemic candidiasis treatment and prophylaxis in much of the world.​ 

C auris, characterized by its high drug resistance and adherence to surfaces, was initially identified in 2009. In 2016, the US Centers for Disease Control and Prevention issued an alert about the global emergence of the multidrug-resistant species C auris. In 2021, the number of clinical cases of C auris in the US rose by 95%, with 17 states identifying their first C auris case from 2019 to 2021.[15] In 2021 in the European Union and European Economic Area, there were 655 reported cases of C auris from 13 countries.[16]​ In 2023, there were 4514 new clinical cases of C auris in the US, indicating a significant increase in infections.[17]​ The SENTRY surveillance program shows significant increase in frequency of C auris: ≤0.1% before 2018, 0.4% to 0.6% from 2018 to 2021, and 1.6% in 2022 of all candida isolates looked at.[18]​ Hospitals are advised to identify all invasive Candida isolates to species level in order to institute specific infection control measures when C auris is isolated.[19]​ These include contact precautions, often for prolonged periods if colonization persists, and cleaning and disinfecting the patient care environment with products effective against Clostridium difficile spores, as standard disinfectants may not eradicate the organism.[19]​​

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