Resurgence of multidrug-resistant tuberculosis during the COVID-19 pandemic in Korea
Article information
Abstract
Background
The coronavirus disease 2019 pandemic, which emerged in 2020, disrupted healthcare systems globally, affecting tuberculosis (TB) diagnosis and reporting. This study assessed the impact of the pandemic on the incidence of TB, multidrug-resistant TB (MDR-TB), and TB-related deaths in Korea between 2016 and 2023.
Methods
Data from annual reports from 2016 to 2023 were used to analyze the incidence of TB and MDR-TB, as well as TB-related deaths. Trends before and after the pandemic were compared to assess the pandemic’s impact on TB management. Key variables included age and sex-based TB incidence, MDR-TB incidence, and number of TB-related deaths.
Results
From 2016 to 2023, the total number of TB cases declined from 39,245 to 19,540, while new TB cases dropped from 30,892 to 15,640, representing reductions of 50.2% and 49.4%, respectively. The most pronounced decline occurred between 2020 and 2023. Individuals ≥65 years of age consistently had the highest TB burden, although the number of cases decreased by 28.6%. MDR-TB cases declined to 399 in 2020 but subsequently rose to 551 in 2023. TB-related deaths decreased from 2,186 in 2016 to 1,322 in 2022, with most deaths occurring in individuals ≥65 years of age.
Conclusions
While the incidence of TB and TB-related deaths decreased during the study period, MDR-TB exhibited an upward trend after 2020. Continued monitoring is needed to understand whether these changes were driven by pandemic-related disruptions or healthcare improvements.
Introduction
Tuberculosis (TB) remains a major global health problem, affecting millions of individuals worldwide each year. Despite progress in disease control, TB continues to cause high rates of illness and death, particularly in countries with a heavy disease burden [1]. Korea has tried to reduce TB cases through a national program focusing on early detection, timely treatment, and ongoing public health interventions [2,3]. However, multidrug-resistant TB (MDR-TB) remains a serious issue because it does not respond to common TB medications, making treatment more difficult. While the overall number of TB cases has decreased, MDR-TB requires close attention to reduce its negative impact on public health [4]. Although the number of MDR-TB cases in Korea has declined, it remains a significant challenge for healthcare systems and public health [5].
The novel coronavirus disease 2019 (COVID-19) pandemic, which began in 2020, has significantly affected healthcare systems worldwide, including the management of TB. With resources being redirected to address COVID-19, routine TB services, such as diagnosis, treatment, and case reporting, have experienced disruptions. These challenges have strained healthcare infrastructure and delayed TB care, likely resulting in underreporting [6]. The effects of these disruptions on the incidence of TB and MDR-TB during the pandemic in Korea remain largely unexplored [7].
As such, the present investigation aimed to assess how the COVID-19 pandemic has affected the incidence of TB, TB-related deaths, and MDR-TB trends in Korea between 2016 and 2023. By comparing pre- and post-pandemic data, this study aimed to understand how healthcare disruptions during the pandemic have affected TB management and outcomes.
Methods
Ethical statements: This study was approved by the Gyeongsang National University Changwon Hospital Institutional Review Board (IRB) (IRB No. GNUCH-2025-01-007). It was exempt from additional ethics review as it used publicly available, anonymized data from the Korea Disease Control and Prevention Agency (KDCA) without access to individual-level patient information. Institutional guidelines and relevant regulations were used to conduct the study.
1. Study design and data sources
The retrospective observational study used publicly available data from annual reports addressing TB and MDR-TB published by the KDCA [8]. Data from 2016 to 2023 were extracted from these reports to examine trends in the incidences of TB and MDR-TB. KDCA reports provide comprehensive nationwide data, including the annual number of new TB and MDR-TB cases. These reports serve as reliable sources of TB surveillance data in Republic of Korea.
2. Description of cases/participants
This study examined all newly reported cases of TB and MDR-TB in Korea between 2016 and 2023. TB cases were defined based on clinical, radiological, and/or bacteriological evidence of Mycobacterium tuberculosis. MDR-TB cases are resistant to isoniazid and rifampicin, the two key first-line anti-TB drugs. The data were organized using annual case numbers and categorized according to age.
3. Data collection and variables
Variables analyzed in this study included the annual number of newly diagnosed TB cases, the number of MDR-TB cases diagnosed each year, and the incidence rate of new TB and MDR-TB cases per 100,000 individuals, adjusted for population size. TB cases were stratified into four age groups: ≤19, 20–49, 50–64, and ≥65 years. The proportion of MDR-TB cases relative to the total number of TB cases and the distribution of TB cases across these age groups were also examined. Furthermore, the study assessed TB-related deaths, categorizing deaths according to age group to evaluate the impact of TB on different age populations.
4. Statistical analysis
Descriptive statistics were used to summarize the annual numbers of TB, MDR-TB-, and TB-related deaths from 2016 to 2023. Data were stratified according to age group (i.e., ≤19, 20–49, 50–64, and ≥65 years), and incidence rates were calculated per 100,000 individuals. A time-series analysis was performed to assess trends in TB and MDR-TB incidence, as well as the number of TB-related deaths throughout the study period. Data visualization, including graphing, was performed using Prism ver. 10 (GraphPad Inc.) to present trends and age group distributions.
Results
1. TB incidence trends
From 2016 to 2023, the total number of TB cases in Korea decreased from 39,245 to 19,540—a 50.2% reduction. Similarly, new TB cases declined from 30,892 to 15,640, corresponding to a 49.4% decrease. The incidence rate of total TB per 100,000 population dropped from 76.8 to 38.2, while that of new TB cases decreased from 60.4 to 30.6 during the same period. The most pronounced reductions were observed between 2020 and 2023 (Fig. 1). All incidence rates were adjusted for population size.
Total and new tuberculosis (TB) cases by age group in Korea, 2016–2023. The left Y-axis represents the total and new number of TB cases, while the right Y-axis shows incidence per 100,000 population. Over the study period, both total and new TB cases declined steadily across all age groups. Individuals aged ≥65 years consistently accounted for the largest number of cases and the highest incidence rates.
2. Age- and sex-based distribution of TB cases
Individuals aged ≥65 years consistently accounted for the highest number of new TB cases throughout the study period. In 2016, this group reported 12,145 cases, which decreased to 8,667 by 2023—a 28.6% reduction. Despite the decline, this group still represented 26.8% of new TB cases in 2023. TB incidence also declined across all younger age groups. Notably, the largest proportional decrease was seen in the 20–49 age group, which experienced a 65% reduction, while individuals aged ≤19 years showed a decline from 882 cases in 2016 to 111 in 2023. Similar downward trends were observed in the 50–64 years age group. Sex-based analysis indicated that males consistently had more new TB cases than females. In 2023, 9,302 cases were reported in males and 6,338 in females, with men accounting for 59.5% of new TB cases. However, both sexes showed similar declining trends in incidence throughout the study period.
3. MDR-TB cases
The number of MDR-TB cases fluctuated throughout the study period. From 852 cases in 2016, annual counts declined to 580 in 2019, reaching the lowest level in 2020 with 399 cases. This was followed by an increase to 560 cases in 2022 and a slight decline to 551 in 2023 (Fig. 2). While the absolute number of TB cases decreased over time, the proportion of MDR-TB cases among total TB cases increased—from 2.2% in 2016 and 2.0% in 2020 to 2.8% in 2023. An age-stratified analysis revealed that individuals aged ≥65 years accounted for the majority of MDR-TB cases across the study period. In contrast, the number of MDR-TB cases in younger age groups—particularly among those aged ≤19 years—remained low and further declined by 2023.
New multidrug-resistant tuberculosis (MDR-TB) cases by age group in Korea, 2016–2023. Annual MDR-TB cases fluctuated throughout the study period, with the highest numbers observed in the ≥65 age group. Case counts in younger age groups (especially those ≤19 years) remained low and showed a slight decreasing trend.
4. TB-related deaths
TB-related deaths declined markedly between 2016 and 2022, falling from 2,186 to 1,322—a 39.5% reduction. The majority of these deaths occurred in individuals aged ≥65 years, with deaths in this group decreasing from 1,891 to 1,157 over the same period. TB-related deaths among individuals under 19 years of age were rare, with no reported cases throughout the study period (Fig. 3).
Tuberculosis (TB)-related deaths by age group in Korea, 2016–2022. The majority of TB-related deaths occurred in individuals aged ≥65 years, while deaths in younger age groups remained consistently low. A declining trend in TB mortality was observed over time, particularly among the elderly population.
Discussion
The present study analyzed trends in TB and MDR-TB in Korea from 2016 to 2023, with a focus on the impact of the COVID-19 pandemic. The findings highlighted significant changes in TB incidence, TB-related deaths, and MDR-TB trends during the study period, emphasizing both achievements and challenges in TB control.
The most significant trend observed was a consistent reduction in total and new TB cases. The decline in TB cases was most pronounced between 2020 and 2023, coinciding with the COVID-19 pandemic. Public health measures, such as wearing masks, social distancing, and restricting movement, likely played a role in reducing TB transmission during this period [9,10]. However, disruptions in healthcare services, including reduced access to diagnostic and treatment facilities, may have also contributed to fewer reported cases by limiting the identification of new cases [6,11,12].
Age-based analysis revealed that TB was a significant burden on older adults throughout the study period, in which individuals ≥65 years of age consistently accounted for the highest proportion of new TB cases. The increased burden of TB in this age group can be attributed to the natural decline in immune function associated with aging―known as immunosenescence―which reduces the body’s ability to effectively combat infections such as TB [13]. Furthermore, older adults are at higher risk for latent TB reactivation, wherein dormant M. tuberculosis bacteria are active [14]. This reactivation is more common due to age-related factors, such as chronic disease(s), malnutrition, and other conditions that weaken the immune system, rendering older individuals more vulnerable to developing active TB [15,16]. This finding underscores the need for focused public health interventions targeting the elderly, who are particularly vulnerable to TB and its complications [17].
The number of MDR-TB cases varied over the study period. Cases decreased from 852 in 2016 to 580 in 2019, with the lowest point in 2020 (399 cases), coinciding with the start of the COVID-19 pandemic. However, numbers increased again to 560 in 2022, with a slight drop to 551 in 2023. In contrast, total TB cases showed a steady decline. This difference may be due to reduced access to care and changes in health-seeking behavior during the pandemic. While TB transmission likely decreased due to public health measures like mask-wearing and distancing, many people may have delayed or missed TB testing, leading to fewer diagnoses. MDR-TB requires longer and more complex treatment and may have been more affected by care disruptions. The post-pandemic increase in MDR-TB may reflect delays in diagnosis and treatment during the early pandemic, resulting in a backlog of undetected cases [18-20]. These trends suggest that the pandemic affected TB care differently depending on disease severity. MDR-TB patients are especially vulnerable to treatment delays, which increase the risk of poor outcomes and continued spread.
TB-related deaths decreased by 39.5% from 2016 to 2022, with most occurring in individuals aged ≥65 years. This trend may reflect improved outcomes in drug-susceptible TB, which represents the majority of cases. The rise in MDR-TB during the later pandemic period likely reflects delayed diagnosis rather than increased disease severity. Moreover, potential underreporting during the pandemic complicates mortality assessment. The simultaneous increase in MDR-TB and decrease in TB-related deaths is not necessarily contradictory but highlights the pandemic’s complex and uneven effects on TB care. Nonetheless, the persistently high mortality among older adults underscores the need for targeted interventions such as early detection and tailored treatment strategies in this vulnerable group [21,22].
The present study had some limitations. First, the data were obtained from national reports, which may have been delayed or erroneous, particularly during the COVID-19 pandemic, and could have affected the accuracy of the TB and MDR-TB results. Second, the study did not consider personal factors, such as other health conditions or socioeconomic status, which may have influenced TB outcomes. Additionally, the analysis focused on national data and did not explore regional differences, which could help identify local challenges in TB control. Finally, while this study highlights disruptions in healthcare during the pandemic, it does not fully assess the extent to which these disruptions impacted TB and MDR-TB trends.
In conclusion, the results of this study demonstrate that although TB incidence and death significantly declined over the study period, fluctuations in MDR-TB trends highlight the ongoing challenges in managing drug-resistant TB, particularly during the COVID-19 pandemic. To sustain progress in TB control, it is essential to strengthen TB surveillance, ensure consistent access to diagnostics and treatment, and prioritize interventions for vulnerable populations, particularly older adults.
Notes
Conflicts of interest
No potential conflict of interest relevant to this article was reported.
Funding
This study was supported by the Development Fund Foundation of Gyeongsang National University in 2024.
Author contributions
Conceptualization: HCK. Formal analysis: THK, HCK. Funding acquisition: HCK. Investigation: HCK. Methodology: THK, HCK. Software: THK. Supervision: HCK. Validation: THK, IRH, HCK. Visualization: THK, HCK. Writing - original draft: THK. Writing - review & editing: THK, IRH, HCK. All authors read and approved the final manuscript.