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Influenza activity in Hong Kong back to baseline level

     The latest surveillance data from the Centre for Health Protection (CHP) of the Department of Health shows that local influenza activity has returned to baseline level since it started to increase in mid-January.

     The weekly number of influenza detections recorded by the Public Health Laboratory Services Branch of the CHP has decreased from its peak of 235 in the week ending March 23 to 81 in the week ending May 25. The latest laboratory data also shows that only around 3.4 per cent of respiratory specimens received during the period from May 13 to May 19 were positive for influenza viruses. The influenza A(H1N1)2009 virus predominated in the past four months, constituting 72 per cent of all influenza detections, followed by influenza A(H3N2) (24 per cent) and influenza B (4 per cent). The viruses circulating so far remain well-matched with the vaccine viruses for the 2012-13 season.

     There has also been a significant reduction in the number of influenza-like illness (ILI) outbreaks reported from schools and institutions, decreasing from 13 in the week ending March 16 to four in the week ending May 25.

     In the week ending May 25, the average ILI consultation rates among sentinel private doctors and general outpatient clinics (GOPCs) were 41.0 per 1 000 consultations and 3.1 per 1 000 consultations respectively. The peak rate recorded for sentinel private doctors was 53.7 in the week ending March 30 while that of GOPCs was 4.9 in the week ending February 16.

     During the period of enhanced surveillance for cases with influenza-associated intensive care unit (ICU) admission or death from January 18 to May 24, a total of 70 ICU admissions or death cases (including 29 deaths) with laboratory confirmation were recorded, aged from 28 to 97 (median: 64). The most affected age group was the elderly aged 65 or above, constituting 49 per cent of all cases.

     In addition, the CHP has continued to monitor paediatric cases (aged below 18) with severe influenza-associated complications or death. Since January 1, there have been 10 reports of severe paediatric influenza-associated complications, aged from 5 months to 15 years (median: 3.5 years). No death cases were recorded among these cases.

     The CHP will continue to closely monitor the surveillance data on influenza and publish weekly reports in the Flu Express on the CHP's website ( to provide updates on the latest local influenza situation.

Ends/Thursday, May 30, 2013
Issued at HKT 16:36


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