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Vaccination urged amid sustained increase in influenza activity outside Hong Kong and local cold weather
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     The Centre for Health Protection (CHP) of the Department of Health today (December 17) again urged the public to get vaccinated early against seasonal influenza in view of the recent local cold weather and the winter influenza season which is expected to arrive in the coming few weeks.

     "Recent surveillance data showed a sustained increase in influenza activity in various travel destinations popular among Hong Kong people and influenza A(H3N2) has been the major circulating virus in and outside Hong Kong. Both trivalent and quadrivalent influenza vaccines recommended by the CHP's Scientific Committee on Vaccine Preventable Diseases for this season cover influenza A(H3N2) and can provide protection against infection," a spokesman for the CHP said.

Surveillance data outside Hong Kong
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     The latest surveillance data from a number of health authorities outside Hong Kong indicate further increases in influenza activity recently.

     In Beijing, the number of cases of influenza-like illness (ILI) has been increasing since the week ending November 16 and exceeded the threshold in the following two weeks. Laboratory surveillance showed that the percentage positive for influenza viruses increased from 10.95 per cent in the week ending November 16 to 26.01 per cent and 24.29 per cent in the following two weeks, and the majority is influenza A(H3N2).

     The influenza season in Japan started earlier than usual. The rate of ILI reported in sentinel sites rose from 1.90 in the week ending November 30 to 3.49 in the week ending December 7, exceeding the level of 1.00 which indicates the start of the season. The number of positive influenza virus detections in public health institutes increased from 89 between November 10 and 23 to 116 between November 24 and December 7, while over 90 per cent are influenza A(H3N2).

     Influenza activity in the United States has also been on the rise. Out-patient surveillance revealed that 2.6 per cent and 2.5 per cent of patient visits were due to ILI in the two weeks ending November 29 and December 6 respectively, which were above the national baseline of 2.0 per cent. The percentage of specimens that tested positive for influenza viruses under laboratory surveillance further increased from 14.5 per cent in the week ending November 22 to 21.2 in the week ending December 6, while over 90 per cent were influenza A with H3N2 being the major subtype.

     Canada recorded continued increases in influenza activity as well. The percentage positive for influenza viruses significantly increased for the third consecutive week, from 8.6 per cent in the week ending November 22 to 15.2 per cent and 19.5 per cent in the two following weeks. The national ILI consultation rate rose from 29.1 per 1 000 consultations in the week ending November 29 to 44.3 in the next. Laboratory-confirmed outbreaks of influenza A continued to increase, particularly in long-term care facilities (LTCFs), as 37 outbreaks were newly reported in the week ending December 6 of which 32 (86 per cent) involved LTCFs, rising from 18 (including 16 in LTCFs, 89 per cent) and 21 (17 in LTCFs, 81 per cent) in the preceding two weeks. To date, 95 per cent of influenza detections have been influenza A with H3N2 as the most common subtype. In both laboratory detections and hospitalisations, the majority of cases were seniors aged 65 and above.

     Of note, in the US and Canada, laboratory analyses revealed that some H3N2 viruses detected in this season were different from the H3N2 virus in the influenza vaccine recommended by the World Health Organization for 2014/15 in the northern hemisphere, but most of the other viruses identified are the same as those covered by the vaccine. According to the Centers for Disease Control and Prevention in the US, influenza vaccine remains the single best way to prevent influenza as it protects against the strains covered in the vaccine and may have some effectiveness against a drifted strain. In addition, antibodies created upon vaccination with one strain often cross-protect against different but related strains of influenza viruses.

     Separately, influenza activity in the United Kingdom also started to increase recently. Laboratory surveillance in England showed that the percentage of specimens that tested positive for influenza viruses rose from 4.6 per cent in the week ending November 29 to 8.1 per cent in the next week, while about 95 per cent were influenza A with H3N2 being the major subtype.

Local surveillance data
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     Locally, overall influenza activity remains at a low level, but some data showed that activity has increased slightly compared with the past few weeks. The percentage of specimens that tested positive for influenza viruses by the CHP's Public Health Laboratory Services Branch increased from 1.76 per cent in the week ending December 6 to 3.52 per cent in the next week. Based on the previously observed seasonality, it is expected that the winter influenza season will arrive in the coming few weeks.

     "As influenza activity outside Hong Kong continues to increase and in view of the local cold weather, we again urge the public to get vaccinated early for personal protection as the immune response takes about two to four weeks to develop. Vaccination is one of the effective means to prevent influenza, its complications and associated hospitalisations and deaths," the spokesman said.

     Pregnant women, the elderly, young children and persons with underlying illnesses are strongly advised to promptly get vaccinated as influenza can cause serious complications in high-risk groups. Given that influenza vaccine is safe and effective, and that serious influenza infections can occur even in healthy individuals, seasonal influenza vaccination is recommended for all persons aged 6 months or above, except those with known contraindications.

     "The public should consult their family doctors for details and arrangements. We urge eligible young children and elderly persons to come forward for vaccination under the Vaccination Subsidy Schemes (VSS) with increased subsidies from $130 to $160 per dose while eligible groups under the Government Vaccination Programme (GVP) should also get vaccinated early," the spokesman added.

     As of December 14, about 188 000 and 175 000 doses of seasonal influenza vaccines have been administered to eligible groups respectively under the VSS and the GVP 2014/15.

     Members of the public are reminded to take heed of the following preventive measures against influenza and other respiratory illnesses:

* Build up good body immunity by having a proper diet, regular exercise and adequate rest, reducing stress and avoiding smoking;
* Maintain good personal and environmental hygiene;
* Wash hands after sneezing, coughing or cleaning the nose;
* Maintain good ventilation;
* Avoid visiting crowded places with poor ventilation; and
* Wear surgical masks and seek medical advice promptly if symptoms of respiratory tract infections or fever develop.

     The public may visit the CHP's influenza page (www.chp.gov.hk/en/view_content/14843.html) for more information on influenza and its prevention.

Ends/Wednesday, December 17, 2014
Issued at HKT 16:38

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