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The Centre for Health Protection (CHP) of the Department of Health today (January 21) reported the latest surveillance data after the arrival of the winter influenza season announced on December 31, 2014, and again urged the public to heighten vigilance and get vaccinated early against seasonal influenza.
"Hong Kong has entered an influenza peak period and the public should maintain strict personal hygiene. Wear a mask when respiratory symptoms develop. Avoid going to crowded places; high-risk persons may wear masks in such places. Wash or clean hands frequently, especially before touching the mouth, nose or eyes, or after touching public installations such as handrails or door knobs," a spokesman for the CHP said.
"As local and global influenza activity continues to increase with the influenza A(H3N2) virus predominating so far in the northern hemisphere, and with an antigenically drifted H3N2 strain which can negatively impact vaccine effectiveness for H3N2 having been detected, vaccination remains an important means to prevent influenza with a certain degree of cross-protection against different but related strains, and to reduce disease severity, hospitalisations and deaths, particularly for high-risk groups," the spokesman added.
Local surveillance
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Among respiratory specimens received by the CHP's Public Health Laboratory Services Branch, the percentage tested positive for influenza viruses increased from 9.22 per cent in the week ending December 27, 2014, to 29.03 per cent last week. Over 90 per cent of influenza virus detections were A(H3N2).
Regarding influenza-like illness (ILI), the number of institutional outbreaks reported to the CHP significantly rose from eight (affecting 53 persons) in the first week of 2015 to 41 (243 persons) last week. As of yesterday (January 20), 26 outbreaks (129 persons) had been recorded this week. The outbreaks in the past four weeks mainly occurred in residential care homes for the elderly (37 per cent), primary schools (25 per cent) and kindergartens or child care centres (18 per cent).
In addition, the ILI consultation rates reported by both sentinel general out-patient clinics (GOPCs) and private doctors increased. In GOPCs, the rate rose from 5.3 ILI cases per 1 000 consultations in the first week to 7.2 last week, while that among private doctors rose from 39.5 to 57.9 in the same period.
Turning to severe cases, as of noon today, 70 cases of influenza-associated admission to intensive care units or death (including 31 deaths) among patients aged 18 or above had been recorded under the enhanced surveillance in collaboration with public and private hospitals reactivated since January 2, 2015. Among them, 66 were influenza A(H3N2), three were influenza B and one was influenza A pending subtype. In the last winter season in early 2014, 266 cases (133 deaths) were filed.
To date, four cases of severe paediatric influenza-associated complication (no deaths) among those aged under 18 years were reported this year via the ongoing reporting system and all were influenza A(H3N2). In 2014, 27 cases (four deaths) were filed.
Situation of neighbouring and overseas areas
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A number of neighbouring and overseas areas in the northern hemisphere have also entered the winter season, including Taiwan, Japan, the United States (US), Canada, the United Kingdom (UK) and Europe while influenza A(H3N2) has also been the major circulating virus. Data so far has shown that all viruses detected in this season remained sensitive to the antivirals oseltamivir (Tamiflu) and zanamivir (Relenza).
In Taiwan, the percentage tested positive for influenza viruses increased from 3.7 per cent in the week ending December 13, 2014, to 11.8 per cent in that ending December 27, 2014. The number of influenza virus detections in Japan rose from 29 in the week ending November 9, 2014, to 263 in that ending December 21, 2014.
The percentage tested positive for influenza viruses in the US ranged from 20.2 to 31.2 per cent from December 14, 2014, to January 10, 2015. In the same period, that in Canada ranged from 28.5 to 34.6 per cent. Canada also recorded 152 outbreaks of influenza A in long-term care facilities in the week ending January 10, 2015, a record high over the past five influenza seasons.
In the week ending January 11, 2015, the percentage tested positive for influenza viruses in England reached 25.0 per cent, exceeding the threshold level of 6 per cent, while that in Europe rose to 28 per cent, which is over the threshold of 10 per cent.
Antigenic drift of H3N2 strain
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According to the World Health Organization (WHO), antigenically drifted H3N2 strains, from A/Texas/50/2012 (vaccine strain recommended by WHO for northern hemisphere 2014/15) to A/Switzerland/9715293/2013, have been observed in increasing numbers after its recommendation in February 2014.
The antigenic drift can negatively impact the vaccine effectiveness for H3N2, but it is expected that the vaccine would afford some cross-protection against currently circulating H3N2 viruses, and also reduce the likelihood of severe outcomes such as hospitalisations and deaths.
"We have been closely monitoring local and global influenza activity, circulating virus strains and the effectiveness of influenza vaccines. The WHO will convene a meeting in February on influenza vaccine composition for the influenza season 2015/16 in the northern hemisphere. The CHP's Scientific Committee on Vaccine Preventable Diseases will continue to closely monitor recommendations by the WHO and other health authorities," the spokesman remarked.
Locally, as of January 18, 2015, about 219 000 and 212 000 doses of seasonal influenza vaccines have been administered to eligible groups under the Government Vaccination Programme and the Vaccination Subsidy Schemes 2014/15 respectively.
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;
* 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 vaccination schemes page (www.chp.gov.hk/en/view_content/17980.html); and
* The list of participating doctors (www.chp.gov.hk/en/view_content/34664.html).
Ends/Wednesday, January 21, 2015
Issued at HKT 18:15
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