Three primary schools and a kindergarten reported flu cases yesterday, bringing to five the number of schools to report cases since the Easter holiday ended on March 31. The Centre for Health Protection was notified yesterday of 18 students with flu-like symptoms in schools in Tsuen Wan, Aberdeen, San Po Kong and Cheung Sha Wan. Three were admitted to hospital, including a three-year-old. A secondary school reported four cases of flu on Monday.