J Korean Med Sci.  2025 Mar;40(11):e38. 10.3346/jkms.2025.40.e38.

Incidence and Temporal Dynamics of Combined Infections in SARS-CoV-2-Infected Patients With Risk Factors for Severe Complications

• Ham SY
• Lee S
• Kim MK
• Jeon J
• Lee E
• Kim S
• Choi JP
• Jang HC
• Park SW

• KMID: 2566250
• DOI: http://doi.org/10.3346/jkms.2025.40.e38

Abstract

Background
Coronavirus disease 2019 (COVID-19) is a newly emerged infectious disease that needs further clinical investigation. Characterizing the temporal pattern of combined infections in patients with COVID-19 may help clinicians understand the clinical nature of this disease and provide valuable diagnostic and therapeutic guidelines.
Methods
We retrospectively analyzed COVID-19 patients isolated in four study hospitals in Korea for one year period from May 2021 to April 2022 when the delta and omicron variants were dominant. The temporal characteristics of combined infections based on specific diagnostic tests were analyzed.
Results
A total of 16,967 COVID-19 patients were screened, 2,432 (14.3%) of whom underwent diagnostic microbiologic tests according to the clinical decision-making, 195 of whom had positive test results, and 0.55% (94/16,967) of whom were ultimately considered to have clinically meaningful combined infections. The median duration for the diagnosis of combined infections was 15 (interquartile range [IQR], 5–25) days after admission. The proportion of community-acquired coinfections (≤ 2 days after admission) was 11.7% (11/94), which included bacteremia (10/94, 10.63%) and tuberculosis (1/94, 1.06%). Combined infections after 2 days of admission were diagnosed at median 16 (IQR, 9–26) days, and included bacteremia (72.3%), fungemia (19.3%), cytomegalovirus (CMV) diseases (8.4%), Pneumocystis jerovecii pneumonia (PJP, 8.4%) and invasive pulmonary aspergillosis (IPA, 4.8%).
Conclusion
Among COVID-19 patients with risk factors for severe complications, 0.55% had laboratory-confirmed combined infections, which included community and nosocomial pathogens in addition to unusual pathogens such as CMV disease, PJP and IPA.

Keyword

COVID-19; Coinfection; Korea; Bacteremia; Opportunistic Infections

Figure

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  Fig. 1 Flow diagram of the patient selection.COVID-19 = coronavirus disease 2019.

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  Fig. 2 Timelines of the diagnosis of combined infections in coronavirus disease 2019 patients after hospitalization. ‘*’ denotes an outlier value, and ‘o’ represents an extreme value. The number above the vertical line within the box indicates the median value.GPC = gram-positive cocci, GNB = gram-negative bacilli, CMV = cytomegalovirus, PJP = Pneumocystis jirovecii pneumonia.

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