Fungal infections represent a growing global health threat, with over 80 million individuals at high risk of either life-threatening complications or severe outcomes such as vision loss each year¹. An estimated 6.55 million people develop serious fungal diseases annually, and more than half of them—approximately 3.75 million—do not survive. These estimates are largely modeled from the prevalence of underlying risk factors, including human immunodeficiency virus (HIV), hematologic malignancies, pulmonary tuberculosis, chronic obstructive pulmonary disease (COPD), and critical illness, due to the unavailability of comprehensive global diagnostic access and surveillance systems². Prospective studies, particularly those including people living with HIV, have revealed that the true burden of fungal disease is often underestimated. Fungal diseases span a wide clinical spectrum, ranging from acute and fatal infections such as cryptococcal meningitis and fungal keratitis to chronic conditions like chronic pulmonary aspergillosis and tinea capitis, as well as recurrent mucosal infections including vulvovaginal and oropharyngeal candi- diasis^3-8. Herein, we review the global and national epidemi- ology of serious fungal infections, with a particular focus on the burden, patterns, and surveillance data from South Korea.

GLOBAL INCIDENCE OF SEVERE FUNGAL DISEASE

Current global estimates emphasize the substantial and often underrecognized burden of severe fungal infections. According to these estimates, over 6.5 million individuals develop invasive fungal diseases annually, resulting in approxi- mately 3.75 million deaths, with approximately 2.5 million of them directly attributable to these infections_⁹. Invasive aspergillosis is the most prevalent fungal infection, with an estimated annual occurrence of over 2.1 million cases, pri- marily affecting those with COPD, malignancies, or patients in intensive care units. Following this is chronic pulmonary asper- gillosis (CPA), with 1.8 million new cases each year, mainly as a consequence of pulmonary tuberculosis. Candidemia and invasive candidiasis together affect approximately 1.56 million people annually, while Pneumocystis pneumonia and cryptococcal meningitis account for more than 500,000 and 190,000 cases annually, respectively. The mortality rates for these conditions are disproportionately high, especially for cryptococcal meningitis (75.8%) and invasive aspergillosis (up to 85.2%), primarily due to delayed diagnosis, limited access to diagnostic tools and antifungal treatments, and a lack of awareness about the diseases. Due to the accumulation of national burden studies, which are now available for more than 80 countries including India, Mexico, and Belgium^10-12, global estimates are becoming more and more precise. In India, a nationwide study estimated over 1.8 million annual cases of CPA, primarily driven by the country's high tuber- culosis burden and further complicated by co-infection and diagnostic overlap¹⁰. In Mexico, a national burden study estimated that serious fungal infections affect approximately 2.7 million people annually, accounting for about 2.45% of the population, with more than 10,000 associated deaths. The most common conditions included recurrent vulvovaginal candidiasis, CPA, and invasive candidiasis. Endemic mycoses such as histoplasmosis and coccidioidomycosis remain under- diagnosed due to limited surveillance and diagnostic cap- acity¹¹. A nationwide multicenter study conducted in Belgium revealed substantial variability in candidemia incidence, ranging from 0.07 to 1.43 cases per 1,000 admissions. The study also reported high fluconazole resistance in C. tropicalis (20%) and C. glabrata (11.3%) and demonstrated that the use of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) significantly improved reporting time for species identification and susceptibility testing¹².

EPIDEMIOLOGY OF FUNGAL INFECTIONS IN KOREA

The epidemiology of fungal infections in the Republic of Korea is influenced by the nation's demographic composition and the high prevalence of underlying conditions such as tuberculosis and cancer. It is estimated that approximately one million people—2.1% of the country's population—are affected by fungal infections each year¹³. Among invasive infections, the estimated incidence (per 100,000 persons) is 4.12 for candidemia, 4.48 for invasive aspergillosis, 0.51 for Pneumocystis pneumonia, and 0.09 for cryptococcal menin- gitis. CPA, with an incidence of 22.4 per 100,000, is notably prevalent, reflecting Korea's residual burden of pulmonary mycobacterial disease. Additionally, oral and esophageal candidiasis exhibit high prevalence rates (539 and 290 per 100,000, respectively), likely due to the high proportion of immunocompromised persons in the population and broad diagnostic criteria.

A previous multicenter study conducted in South Korea investigated antifungal usage patterns, species distribution, and antifungal susceptibility profiles across 10 hospitals¹⁴. Fluconazole emerged as the most frequently used antifungal drug, followed by Amphotericin B. Out of 274 clinical isol- ates of Candida, C. albicans was the most commonly found species. However, non-albicans species like C. glabrata and C. parapsilosis showed significant resistance, especially to fluconazole. A notable 20.7% of all isolates exhibited non-susceptibility to fluconazole, highlighting a rising concern in antifungal management.

In late 2020, South Korea experienced a notable outbreak of fungal endophthalmitis following cataract surgery¹⁵. Although the incidence of fungal endophthalmitis is extremely low (0.002%), this rare nationwide event affected 281 eyes of 265 patients. Of the 260 samples cultured, 103 (39.6%) tested positive for fungal organisms, with Fusarium oxysporum being the predominant species. The outbreak was linked to a contaminated brand of viscoelastic material, prompting a government-led epidemiological investigation and subsequent recall. Through intensive treatment, including early vitrec- tomy and repeated intravitreal antifungal injections, visual outcomes were generally positive, with over 93% of cases achieving disease remission within six months.

CUTANEOUS FUNGAL INFECTIONS IN KOREA

A nationwide multicenter study investigated the clinical features and culprit pathogens of deep cutaneous fungal infections in Korea between 2006 and 201016. Sixteen academic dermatology centers participated, of which 11 were located in the capital region. Approximately half of the 51 identified cases were attributed to opportunistic infections in immunocompromised patients, while the remaining were caused by primary pathogens. Candida and Sporothrix were the most frequently isolated organisms. Comorbid condi- tions were observed in 30 patients, including 26 who were immunosuppressed—most commonly due to organ trans- plantation or hematologic malignancies. Eight patients, all of whom were immunocompromised, died during hospital- ization. Another prospective multicenter study conducted at 13 tertiary hospitals in Korea from 2016 to 2017 investigated the epidemiologic and mycologic characteristics of superficial dermatomycoses¹⁷. Among 453 patients, tinea corporis was the most common diagnosis, followed by tinea pedis and tinea unguium, while tinea capitis predominantly affected children aged below 10 years. There were substantial variations in disease duration across subtypes, with tinea unguium showing the longest courses. Treatment patterns reflected disease severity and site; systemic therapy was more commonly prescribed for tinea capitis and tinea unguium, while topical agents sufficed for milder cases. Fungal culture identified Trichophyton rubrum as the most frequent pathogen overall, particularly in tinea corporis and tinea faciale, whereas Micro- sporum canis was most isolated in tinea capitis. Compared to earlier reports, the proportion of infections caused by T. mentagrophytes and M. canis appeared to have declined, potentially reflecting shifting exposure patterns and host factors in patients encountered at tertiary care centers.

A nationwide retrospective cohort study investigated the relationship between climatological factors and hospital visits for superficial fungal infections using the national health insurance service (NHIS)-national sample cohort from 2003 to 2012¹⁸. Among 116,903 identified patients, the most common infection was tinea unguium (46.7%), followed by tinea pedis and tinea corporis, which differs from the findings of previous studies at conducted tertiary hospitals that emphasized tinea corporis and capitis. Notably, hospital visits showed a significant positive correlation with average daily temperature (r = 0.685, p < 0.001) and relative humidity (r = 0.427, p < 0.001), suggesting that warmer and more humid conditions may contribute to increased incidence and symptom exacerbation of superficial fungal infections. To the best of our knowledge, this is the first population-based study in Korea to establish climatological influences on fungal infection patterns, emphasizing the importance of environ- mental factors in dermatologic disease epidemiology.

This review highlights the distinct and evolving epidemi- ology of fungal infections in Korea, shaped by both global patterns and regional factors. While invasive fungal infections like candidemia and aspergillosis occur at rates similar to those in Western countries, CPA is disproportionately common. Dermatologic studies reveal changing trends in superficial and deep mycoses, and population-based data show significant associations between high temperature, humidity, and in- creased hospital visits. These findings highlight the need for continued surveillance and greater clinical awareness of fungal infections in Korea.