The Centre for Health Protection expects the current summer flu season, which started six weeks ago, to remain highly active for at least one more month as it has yet to reach its peak.

The city recorded its first fatal paediatric flu case this year two days ago – a 13-year-old teenage girl who had not been vaccinated died after catching influenza B.

Centre controller Edwin Tsui said on RTHK on Tuesday it is monitoring the situation of her three classmates, who developed mild symptoms of flu but do not have to be hospitalised.

"Since the start of the school year in September, we have noticed a significant increase in flu outbreaks," he said.

"As of yesterday, we had recorded 390 outbreaks in schools, the majority of which were in secondary and primary schools.

"More than 3,000 people have been affected.

"Over the past four weeks, we have recorded an average of around 70 outbreaks per week. This is far more than the winter flu peak at the beginning of the year, when there were only about 15 cases per week."

Tsui said the reason that the situation this year was more serious was because the current flu season started in September while outbreaks in the past mostly took place between July and August.

People are still getting inoculated against flu, he said, adding that vaccination will be completed by the end of October for more than half of the about 2,300 schools who have joined the vaccination outreach programme.

As the flu season could stretch till at least next month, Tsui does not rule out the possibility of the current season overlapping with winter.

He reiterated that all flu vaccines protect against both influenza A and B viruses, once again urging the public, particularly children and the elderly, to get jabbed as soon as they can.