Influenza

Acute respiratory disease caused by influenza virus (Influenza virus A/B/C/D) infection

1 to 4 days (average 2 days)
From 1 day before the onset of symptoms to 5 to 7 days after onset * However, in children or immunocompromised individuals, the virus shedding period may extend beyond 10 days.

High fever (38 to 40℃), respiratory symptoms such as dry cough and sore throat, as well as general symptoms like headache, muscle pain, fatigue, weakness, and loss of appetite
Accompanied by runny nose, nasal congestion, eye pain, vomiting, and abdominal pain

Vaccination
Proper handwashing and adherence to cough etiquette
Avoidance of touching eyes, nose, and mouth with unwashed hands
During the symptomatic period, limiting visits to workplaces, schools, and public places, and resting at home

Reporting scope: Patients, suspected cases
- (Patient) A person who shows clinical symptoms consistent with influenza and is confirmed to be infected with the infectious pathogen according to diagnostic criteria
- (Suspected case) A person showing fever above 38℃ along with cough or sore throat
Diagnostic criteria: Detection of specific genes in the specimen
Reporting period: Report within 7 days
Responsible department
- (Reporting) Division of Infectious Disease Control
- (Diagnosis) Division of Emerging Infectious Diseases

Clinical Surveillance of Influenza-like Illness (ILI)

Influenza patient
- A person who shows clinical symptoms consistent with influenza and is confirmed to be infected with the infectious pathogen according to diagnostic criteria
Influenza-like illness (ILI)
- A person showing fever above 38°C along with cough or sore throat

Continuous monitoring of trends in the occurrence of influenza-like illness to identify outbreaks early
Provision of foundational data for establishing national influenza control measures

300 outpatient institutions nationwide (pediatrics, internal medicine, family medicine, otorhinolaryngology)
- Weekly surveillance (status reports of influenza-like illness patients among those treated from Sunday to Saturday within 7 days)
Influenza sentinel surveillance (clinical) flowchart

Korea Disease Control and Prevention Agency
- Designation of sentinel surveillance sites
- Analysis of surveillance data and information feedback
City/Province
- Confirming and preparing for influenza outbreak situations Distribution of feedback materials, etc.
- Distribution of feedback materials, etc.
City/County/District Health Center
- Management of sentinel surveillance sites
- Distribution of feedback materials, etc.
Sentinel surveillance institution
- Report the total number of patients treated and the number of influenza-like illness patients to the Korea Disease Control and Prevention Agency

2024-2025 influenza season outbreak criteria ⌜8.6 cases per 1,000 outpatient visits
Before the start of each season (September to the following August), expert advisory meetings will be held to establish outbreak criteria, and an influenza outbreak warning will be issued if the criteria are exceeded. * During an outbreak warning period, antiviral medications are prescribed based on suspected symptoms alone for high-risk groups for influenza (children, pregnant women or mothers within 2 weeks of childbirth, individuals over 65 years old, immunocompromised individuals, and those with underlying conditions) without separate testing, with health insurance coverage applied.

2019-2020절기부터 2024-2025절기까지 주차별 인플루엔자 의사환자 발생분율 추이를 보여주는 선 그래프

Total influenza patients
- New hospitalized patients, outpatients, and emergency room visits diagnosed with influenza
Influenza outpatients
- New outpatients and emergency room patients diagnosed with influenza
Influenza-related deaths
- Among the death cases at sentinel surveillance sites, those who received a confirmed influenza diagnosis within 30 days before death

Monitor hospitalizations and deaths due to influenza each season to assess severity

Sentinel surveillance medical institutions for acute respiratory infections * Designation criteria: Public hospitals and medical institutions with 200 or more beds, and tertiary care hospitals