Influenza activity in HK back to baseline level

     A spokesman for the Department of Health said today (March 31) that the latest surveillance data from the Centre for Health Protection (CHP) showed that influenza activity in Hong Kong has returned to baseline level, indicating the end of the current winter influenza season which had lasted for about two months.

     "Hong Kong entered the winter influenza season in mid January and influenza activity peaked in early February," the spokesman said.

     The weekly number of influenza detections recorded by the Public Health Laboratory Centre of the CHP has decreased from the peak level of 880 in the week ending February 5 to 57 in the week ending March 26. Influenza A (H1N1) 2009 (i.e. human swine influenza) predominated this season, constituting about 90% of all influenza detections.

     In the week ending March 26, the average consultation rate for influenza-like illness (ILI) among general outpatient clinics (GOPCs) and sentinel private doctors was 4.9 per 1,000 consultations and 44.2 per 1,000 consultations respectively. The peak rates recorded this season for GOPCs and sentinel private doctors were 10.7 in the week ending February 5 and 71.3 in the week ending January 29.

     There has also been a decrease in the number of ILI outbreaks occurring in institutions and schools, from 59 and 55 ILI outbreaks in the weeks ending January 22 and 29, to 17 and 13 in the weeks ending March 19 and 26.

     A new case-based surveillance system was set up in collaboration with the Hospital Authority and private hospitals to monitor influenza-associated admissions to intensive care units (ICU) or deaths during influenza peak seasons since January 24, 2011. As at 2pm on March 30, a total of 123 severe cases (69 male and 54 female), including 34 deaths with laboratory confirmation, were recorded.

     The weekly number of reported ICU admissions or deaths reached the peak level of 30 in the week ending February 12. Their ages ranged from 56 days to 87 years (median: 55 years). About 69% had pre-existing chronic disease and only about 5% were known to have received an influenza vaccination.

     Among the 34 fatal cases, the patients' ages ranged from 27 months to 87 years (median: 62 years) and 88% had pre-existing chronic disease. Only two were known to have received seasonal flu vaccination.

     After reviewing the prevailing situation, this case-based surveillance system and the daily update on the CHP website will be discontinued tomorrow (April 1). The CHP will closely monitor surveillance data on influenza and continue to publish weekly reports in the Flu Express on the CHP website to summarise the local influenza situation.

Ends/Thursday, March 31, 2011
Issued at HKT 11:51