A surge in seasonal influenza has been detected, with the average consultation rate for flu-like illness among private doctors rising from 42.8 per 1,000 consultations in the week ending February 20, to 55.1 in the week ending February 27.

The Centre for Health Protection today said the number of patients with fever or respiratory symptoms attending designated flu clinics grew from 410 to 704.

Twenty-eight flu-like illness outbreaks in institutions were recorded, affecting at least 154 people in the first four days of the current week. Influenza virus isolation also rose.

There were 85 influenza detections last week compared with 44 from February 14 to 20. The majority were influenza B virus (63.5%) while human swine influenza virus accounted for 22.4% and influenza A (H3N2) virus about 1% of all isolates.

The currently used seasonal influenza vaccine for the 2009-10 northern hemisphere influenza season is expected to confer certain cross protection against this influenza B virus.