[Establishment of the classified evaluation system on the levels of influenza epidemics through a synthetic index method, in Beijing].

To establish a classified evaluation system for recognizing the levels of influenza epidemics and to explore the new reporting system on influenza epidemics. The following 3 indicators, including 1) the number of influenza-like illness, 2) positive rate of detection on influenza virus nucleic acids, and 3) the number of influenza outbreaks were chosen to calculate the synthetic index and to classify the grades of evaluation. 209 weeks during 2013-2017 were classified into 5 grades: Grade 1 were 110 weeks (52.63%), Grade 2 were 47 weeks (22.49%), Grade 3 were 44 weeks (21.05%), Grade 4 were 8 weeks (3.83%), and Grade 5 were 0 week. This classified evaluation system provided simple, comprehensive and comparable reference indicators and used for the evaluation on influenza epidemics, also providing suggestions for influenza prevention and control accordingly.