BEIJING, Dec. 28 (Xinhua) -- Beijing has entered the flu season.

The activity of flu viruses -- mainly Influenza A/H3N2 and Influenza A/H1N1 -- is still rising, said Pang Xinghuo, deputy director of the municipal center for disease control and prevention.

Over the past week, Beijing's 144 medium- and large- health institutes reported a higher percentage of flu cases than that in the same period last year. But no variations of the viruses have been detected, Pang said in a press conference Thursday.

The center advised the elderly and the minors to take precaution.