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The Centre for Health Protection (CHP) of the Department of Health today (April 1) 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 was still above the baseline. We expect that the local influenza activity would remain so for some time," a spokesman for the CHP said.
"We note that the proportion of influenza B virus in Hong Kong had been on the rise while the influenza B virus also predominated in overseas areas in recent weeks. In the upcoming Easter and Ching Ming Festival holidays, the public should maintain strict personal hygiene both locally and during travel," the spokesman added.
Laboratory surveillance
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The percentage that tested positive for seasonal influenza viruses decreased from 15.1 per cent in the third week of March to 14.5 per cent last week, which is again lower than 15.4 per cent (arrival of season) in the first week of 2015, among respiratory specimens received by the CHP's Public Health Laboratory Services Branch.
Of note, the proportion of A(H3N2) dropped from 82.0 per cent to 76.7 per cent in the last two weeks while that of B correspondingly increased from 14.7 per cent to 20.3 per cent among influenza virus detections. That of A(H1) and C remained low.
"The proportion of B is on the rise. Virus characterisation studies to date show that most detections belong to the Yamagata lineage and very few are from the Victoria lineage, and do not reveal significant differences from the vaccine virus strains, B/Massachusetts/2/2012-like virus (Yamagata) in trivalent influenza vaccine (TIV) as well as quadrivalent influenza vaccine (QIV); and B/Brisbane/60/2008-like virus (Victoria) in QIV, recommended by the World Health Organization for the 2014-15 winter season for the northern hemisphere," the spokesman said.
"Hence, while TIV of the current season may potentially prevent the majority of influenza B locally so far, QIV may potentially offer additional protection against strains of the Victoria lineage, as recommended by the Scientific Committee on Vaccine Preventable Diseases last August. Citizens yet to be vaccinated should do so promptly as it can reduce disease severity, hospitalisations and deaths, particularly for high-risk groups," the spokesman added.
Vaccination
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As of March 29, about 257 000 doses and 248 000 doses of influenza vaccines had been administered to eligible groups under the Government Vaccination Programme and the Vaccination Subsidy Schemes 2014/15 respectively, representing increases of 8 per cent and 5 per cent from the same period of last year.
Severe cases
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From noon yesterday (March 31) to noon today, an additional case of influenza-associated admission to intensive care units or death, including one death, among adults aged 18 or above had been recorded under the enhanced surveillance in collaboration with public and private hospitals reactivated since January 2, while an additional death was recorded among previously reported cases, bringing the total to 581 (439 deaths) so far. Among them, 549 were A(H3N2), eight were A(H1N1)pdm09, six were A pending subtype and 18 were B. In the last winter season in early 2014, 266 cases (133 deaths) were filed.
Last week (from March 22 to 28), 32 cases (23 deaths) were recorded. Separately, a daily average of 2.6 cases (1.9 deaths) were filed in the last seven days (from March 25 to 31), compared with five cases (three deaths) in the preceding seven days (from March 18 to 24).
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 and the total this year hence remains at 18 (one death) and all were A(H3N2). In 2014, 27 cases (four deaths) were filed.
Institutional outbreaks
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Turning to influenza-like illness (ILI), an institutional outbreak affecting three persons was reported to the CHP yesterday (March 31) by a residential care home for the elderly.
The weekly number of outbreaks decreased from 19 affecting 75 persons in the third week of March to 11 (59 persons) last week. As of yesterday, four (15 persons) had been recorded so far this week. Outbreaks in the past four weeks mainly occurred in residential care homes for the elderly (57 per cent) and primary schools (21 per cent).
Neighbouring and overseas areas
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While the influenza activity in a number of overseas areas in the northern hemisphere has peaked and has been decreasing and that of the others remain elevated, the B virus has been increasing by proportion.
In Taiwan, the influenza season has persisted and the percentage that tested positive for influenza viruses stood at a high level of 29.8 per cent in the second week of March. In Europe, the proportion of influenza virus detections in sentinel specimens stood at 41 per cent in the week ending March 22, which is 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 that tested positive for influenza viruses in the United States, Canada and England has also been decreasing but the proportion of B among positive detections has been on the rise.
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 (www.fb.com/CentreforHealthProtection); and
* The YouTube Channel (www.youtube.com/c/ChpGovHkChannel).
Ends/Wednesday, April 1, 2015
Issued at HKT 17:12
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