Press Release

Latest update of surveillance data in winter influenza season

18 March 2015

The Centre for Health Protection (CHP) of the Department of Health today (March 18) reported the latest surveillance data of the winter influenza season, and again urged the public to heighten vigilance and get vaccinated early against seasonal influenza.

"Although the latest surveillance data show that the overall influenza activity continued to decrease, it is still above the baseline. We expect that Hong Kong will remain in the winter influenza season for some time," a spokesman for the CHP said.

Laboratory surveillance

Among respiratory specimens received by the CHP's Public Health Laboratory Services Branch, the percentage positive for seasonal influenza viruses decreased from 19.8 per cent in the first week of March to 17.9 per cent last week, compared with 38.7 per cent (peak) in the last week of January and 15.4 per cent (arrival of season) in the first week of 2015.

Among influenza virus detections, 84.5 per cent were A(H3N2) while 12.6 per cent were B.

Severe cases

From noon yesterday (March 17) to noon today, five additional cases of influenza-associated admission to intensive care units or death (including four deaths) among adults aged 18 or above had been recorded under the enhanced surveillance in collaboration with public and private hospitals reactivated since January 2, bringing the total to 529 (399 deaths) so far. Among them, 497 were A(H3N2), seven were A(H1N1)pdm09, 10 were A pending subtype and 15 were B. In the last winter season in early 2014, 266 cases (133 deaths) were filed.

Last week (from March 8 to 14), 36 cases (29 deaths) were recorded. Separately, a daily average of 6.9 cases (5.1 deaths) were filed in the last seven days (from March 11 to 17), compared with 6.1 cases (5.4 deaths) in the preceding seven days (from March 4 to 10).

Meanwhile, no additional cases of severe paediatric influenza-associated complication or death among children aged under 18 have been reported since yesterday via the ongoing reporting system. The total this year remains at 18 (one death) and all were A(H3N2). In 2014, 27 cases (four deaths) were filed.

Institutional outbreaks

Turning to influenza-like illness (ILI), an institutional outbreak (affecting four persons) was reported to the CHP yesterday (March 17) by a residential care home for the elderly.

The weekly number of outbreaks increased from 11 (affecting 55 persons) in the first week of March to 22 (93 persons) last week. As of yesterday, 10 (40 persons) had been recorded so far this week. Outbreaks in the past four weeks mainly occurred in residential care homes for the elderly (57.2 per cent) and schools (31.9 per cent).

Vaccination

As of March 15, about 255 000 doses and 246 000 doses of influenza vaccines had been administered to eligible groups under the Government Vaccination Programme and the Vaccination Subsidy Schemes 2014/15 respectively, an eight per cent and five per cent increase from the same period of last year.

Neighbouring and overseas areas

The influenza activity in a number of overseas areas in the northern hemisphere has peaked and has been decreasing while that of the others remain elevated, with A(H3N2) virus predominating so far.

Regarding neighbouring areas, the influenza season in Taiwan and Macau persisted. In Taiwan, the percentage positive for influenza viruses stood at a high level of 29.1 per cent in the last week of February.

In Europe, following a consistently high proportion of influenza virus detections of 50 per cent or higher in sentinel specimens since the week ending January 25, it decreased to 41 per cent in the week ending March 8, which is however still over the threshold of 10 per cent.

In Japan, the average number of reported ILI cases per sentinel site has been decreasing. The percentage positive for influenza viruses in the United States, Canada and England has also been decreasing.

The public should maintain good personal and environmental hygiene against influenza and other respiratory illnesses:

• Receive seasonal influenza vaccination for personal protection;
• Wash hands with liquid soap and water properly whenever possibly contaminated;
• When hands are not visibly soiled, clean them with 70 to 80 per cent alcohol-based handrub;
• Wash or clean hands frequently, especially before touching the mouth, nose or eyes, or after touching public installations such as handrails or door knobs;
• Cover the nose and mouth when sneezing or coughing, and wash hands thoroughly afterwards;
• Dispose of soiled tissue paper properly in a lidded rubbish bin;
• Put on a surgical mask when respiratory symptoms develop;
• Maintain good indoor ventilation;
• When influenza is prevalent, avoid going to crowded or poorly ventilated public places; high-risk individuals may consider putting on surgical masks when staying in such places; and
• Maintain a balanced diet, exercise regularly, take adequate rest, do not smoke and avoid overstress.

The public may visit the CHP's pages below for more information:

• The influenza page ( www.chp.gov.hk/en/view_content/14843.html );
• The weekly Flu Express report ( www.chp.gov.hk/en/view_content/2108.html );
• The update on severe seasonal influenza cases ( www.chp.gov.hk/files/pdf/flu_update_en.pdf );
• The vaccination schemes page ( www.chp.gov.hk/en/view_content/17980.html );
• The list of participating doctors ( www.chp.gov.hk/en/view_content/34664.html );
• The Facebook Page ( fb.com/CentreforHealthProtection ); and
• The YouTube Channel ( youtube.com/c/ChpGovHkChannel ).