Figure. . . Influenza surveillance data, Hong Kong, February 23, 2008–June 18, 2011. A) Weekly overall school absenteeism rate. B) Weekly influenza-like illness (ILI)–specific school absenteeism rate. C) Weekly ILI (defined as fever plus cough or sore throat) consultation rates in sentinel networks of outpatient clinics in the private sector. D) Proportion of influenza A and B virus isolations (by date of collection) among all specimens submitted to the reference laboratory for Hong Kong Island at Queen Mary Hospital.