Table 1. Epidemic thresholds for seasonal influenza

Country/region	Epidemic threshold
Korea (KDCA)	-[Mean rate of ILI (per 1,000) during non-influenza weeks for the most recent three seasons+(2×SDs)]-A non-influenza time period is defined as two or more consecutive weeks in which influenza positivity among respiratory laboratory samples is lower than 2%
United States (CDC)	-[Mean percentage of ILI during non-influenza weeks for the most recent two seasons+(2×SDs)]-A non-influenza time period is defined as two or more consecutive weeks in which each week accounted for less than 2% of the season’s total number of specimens that tested positive for influenza
Europe (ECDC)	-10% influenza positivity among respiratory laboratory samples

KDCA, Korea Disease Control and Prevention Agency; CDC, Centers for Disease Control and Prevention; ECDC, European Centre for Disease Prevention and Control; ILI, influenza-like illness.