The Centre for Health Protection (CHP) of the Department of Health today (April 25) announced that, according to the latest surveillance data, local seasonal influenza activity persists at a high level and it is believed that the current influenza season would persist for a period of time. The CHP appealed again to members of the public to heighten their vigilance, and people belonging to high risk priority groups should receive seasonal influenza vaccination (SIV) as soon as possible for prevention of severe disease and death.
Hong Kong has entered the current influenza season since early January this year. According to the latest surveillance data (as at the week ending April 20), the majority of positive detections in that period were influenza A(H1) (around 83 per cent), showing a shift from influenza A(H3) which was the dominating virus during January to March this year. The influenza admission rate in public hospitals has remained at a high level (0.69 cases per 10 000 population) and the latest percentage of respiratory specimens testing positive for seasonal influenza viruses received by the Public Health Laboratory Services Branch of the CHP and Hospital Authority (HA) was also at a high level of 9.76 per cent. Meanwhile, as at the week ending April 20, 29 influenza-like illness outbreaks occurring in schools/institutions were recorded, representing a significant increase as compared to about 10 outbreaks recorded per week in the first half of April. In addition, a total of 20 paediatric cases of influenza-associated complication/death were recorded in this influenza season (including two fatal cases). Three quarters of the cases (15 cases) were known to have not yet received the 2023/24 SIV.
"Seasonal influenza virus strains detected in Hong Kong include influenza A(H1), influenza A(H3) and influenza B viruses, and they are typically more active during influenza seasons. The influenza season in Hong Kong usually lasts for eight to 12 weeks while the duration would be prolonged when there is a transition of the dominating virus strain. For example, in the 2015/16 winter influenza season, influenza A (H1) predominated initially and was then overtaken by influenza B as the predominant strain, resulting in a prolonged season that lasted for about 16 weeks with more severe cases. The CHP observed a gradual change of the predominant strain from influenza A(H3) to influenza A(H1) this season. It is believed that the current influenza season would persist for a period of time and more outbreaks and severe cases might be recorded in the upcoming weeks," a spokesman for the CHP elaborated.
Separately, the CHP has also been continuing its monitoring against other respiratory pathogens. For children, surveillance data as of April 20 revealed that the rhinovirus/enterovirus continued to have the highest activity level among the respiratory pathogens, accounting for 22 per cent of the children respiratory specimens received by the HA. The next active pathogen is adenovirus, with the positive percentage of 8.6 per cent. Meanwhile, according to the figures from the HA, the percentage of positive specimens for Mycoplasma pneumoniae infection in children has increased from about 5 per cent two months ago to 8 per cent currently. The proportion of other respiratory pathogens including respiratory syncytial virus, human metapneumovirus and parainfluenza viruses are at 6.7 per cent, 5.5 per cent and 3.5 per cent respectively.
The spokesman reiterated that many respiratory pathogens including influenza virus may have transmission simultaneously, while vaccination is safe and effective for preventing seasonal influenza. The Scientific Committee on Vaccine Preventable Diseases under the CHP opined that SIV are effective against influenza A (including H1 and H3) and B. Members of the public who have not received SIV, in particular high risk groups such as young children, the elderly and chronic disease patients, should get vaccinated as soon as possible.
The Government has all along been committed in encouraging members of the public to receive SIV. Various SIV programmes and relevant subsidy schemes of the Government have included injectable inactivated influenza vaccines and nasal live attenuated influenza vaccine for citizens to choose. Since the launch of the 2023/24 season SIV programmes from September last year, a total of over 1.84 million doses of SIV have been administered so far, representing an increase of 20 per cent compared with the same period of last season. An obvious increase in SIV uptake this season for high-risk groups has been observed, especially among the elderly and children, when compared with previous years. Currently, about 534 100 doses of SIV have been administered for children aged between 6 months and below 18 years of age. The overall vaccine coverage rate has reached 52.5 per cent. Vaccination at residential care homes for the elderly has covered over 81 per cent of the residents by arranging visiting doctors' outreach vaccination service, while the SIV administered to elders increased by 15 per cent compared to last year, and the overall vaccine coverage rate of elders has reached 50.8 per cent. Members of the public who have not received SIV this current season should consult their family doctors about the vaccines available and receive vaccination as soon as possible for personal protection.
The spokesman reminded that wearing a surgical mask properly could effectively prevent respiratory diseases transmitted through respiratory droplets. High-risk persons should wear a surgical mask when visiting public places, and the public should also wear a surgical mask when taking public transportation or staying at crowded places. Persons who are symptomatic, even if having mild symptoms, should wear a surgical mask, refrain from work or attending classes at school, and seek medical advice promptly with a view to lowering the risk of spreading the virus.
​​The CHP will continue to closely monitor local and overseas situation of infectious diseases. For the latest information, please visit the CHP's influenza page and COVID-19 & Flu Express. As for vaccination, the public may visit the CHP's Vaccination Schemes page.
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