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While nowhere near the levels of last fall, Hong Kong today is reporting a noticeable uptick in the number of flu-like illnesses (ILIs)in their region.
Of the samples that tested positive for influenza last week, more than 60% were from the Influenza B virus.
This summary report from The Centre For Health Protection’s Communicable Diseases Watch Volume 7, Number 5, Week 8 – 9 (February 14 – February 27, 2010) 4 March 2010.
Apparent increase in seasonal influenza activities
Reported by DR ALBERT AU, Medical Officer, AND DR TC SHIU, Senior Medical Officer, Surveillance and Epidemiology Branch, CHP.
Recent data from the influenza surveillance systems of the Centre for Health Protection (CHP) showed apparent increases in influenza activities in the community.
During week 9 (February 21 -27, 2010), the average consultation rate for influenza-like illness (ILI) among sentinel private doctors was 55.1 per 1,000 consultations (Figure 1), as compared with 42.8 in week 8 (February 14 - 20, 2010).
The number of patients with fever/respiratory symptoms attending Designated Flu Clinics (DFCs) also increased from 410 in week 8 to 704 in week 9 (Figure 2).
Besides, the number of institutional ILI outbreaks has increased to 23 in the first four days (February 28 - March 3, 2010) of week 10, as compared with three in week 8 and three in week 9 (Figure 3). 95.7% (22/23) of the recently reported ILI outbreaks occurred in school settings which included 15 primary schools, four kindergartens/child care centres and three secondary schools.
The number of influenza viruses detected from respiratory specimens at the Public Health Laboratory Centre of CHP increased from 44 in week 8 to 85 in week 9 (Figure 4).
In week 9, the majority of influenza isolates were influenza B (63.5%) while HSI virus accounted for 22.4% and seasonal influenza A (H3N2) virus about 1% of all isolates. The circulating influenza B virus was mainly B/ Victoria/2/87 lineage virus.
The currently used seasonal influenza vaccine for the 2009-2010 northern hemisphere influenza season is expected to confer certain cross protection against this influenza B virus.
All the influenza B and influenza A (H3N2) viruses tested remained sensitive to oseltamivir (Tamiflu) while only a very small number of HSI virus was resistant to oseltamivir.
In Hong Kong, the traditional winter seasonal influenza peak usually occurs during February and March and we will closely monitor the influenza activity in the coming one to two weeks in order to confirm the arrival of the traditional winter influenza season.
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