A paediatrician warned on Saturday that the winter and summer flu seasons may be merging, given the rising number of cases.

Mike Kwan from the University of Hong Kong's Department of Paediatrics and Adolescent Medicine said the flu season may not end.

"The number of cases is still increasing. We don't know when the situation will stabilise or even when the numbers will drop. We expect the summer flu season to start soon, so the winter and summer flu seasons may be coming together," he told a radio programme.

Four children had died after contracting influenza, and Kwan said many such cases were complicated with encephalopathy, and their situations could worsen in a matter of hours.

He said the condition could only be alleviated by using drugs like steroids, but the best prevention was to get a flu jab.