J Korean Med Sci.  2023 Feb;38(8):e58. 10.3346/jkms.2023.38.e58.

Incidence, Severity, and Mortality of Influenza During 2010–2020 in Korea: A Nationwide Study Based on the Population-Based National Health Insurance Service Database

• Hwang SH
• Lee H
• Jung M
• Kim SH
• Sung HK
• Oh Md
• Lee JY

• KMID: 2539631
• DOI: http://doi.org/10.3346/jkms.2023.38.e58

Abstract

Background
The epidemiology of influenza is commonly used to understand and establish relevant health policies for emerging respiratory infections, including coronavirus disease 2019 (COVID-19). However, Korea has no confirmed nationwide data on influenza incidence, severity, and mortality rate.
Methods
We conducted a cross-sectional study to obtain epidemic data on influenza at the national level using National Health Insurance claims data during 2010 to 2020. Influenza cases were defined as 90-day timeframe episodes based on all inpatient and outpatient claims data with disease code J09, J10, and J11. Influenza incidence, severity, and mortality rate were calculated, and logistic regressions were performed to assess the associations of demographic characteristics and comorbidity with influenza-related hospitalization, severe illness, and death.
Results
There were 0.3–5.9% influenza cases in the population from 2010 to 2020, with 9.7–18.9%, 0.2–0.9%, and 0.03–0.08% hospitalized, used in the intensive care unit, and dead, respectively. Age-standardized incidence and mortality rates were 424.3–6847.4 and 0.2–1.9 per 100,000 population, respectively. While more than half of the influenza cases occurred in populations aged younger than 20 years, deaths in older than 60 years accounted for more than two-thirds of all deaths.
Conclusion
This study provided the simplest but most important statistics regarding Korean influenza epidemics as a reference. These can be used to understand and manage other new acute respiratory diseases, including COVID-19, and establish influenza-related policies.

Keyword

Epidemiology; Incidence; Severity; Mortality; Influenza; Korea

Figure

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  Fig. 1 Process of data extraction and definition of influenza cases.

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  Fig. 2 Age-standardized incidence of influenza, 2010–2020.Influenza incidence rate was adjusted to 2005 midyear population from Statistics Korea.

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  Fig. 3 The case fatality of influenza, 2010–2020.

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  Fig. 4 Age-standardized influenza-related mortality, 2010–2020.Influenza-related mortality rate was adjusted to 2005 midyear population from Statistics Korea.

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