Influenza activity remains high in Hong Kong and Territory-wide Sewage Surveillance Programme will cover seasonal influenza viruses
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Influenza activity remains at high level
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The CHP's latest surveillance data showed that the percentage of respiratory specimens testing positive for seasonal influenza viruses during the past week (October 19 to 25) was 12.01 per cent, similar to the 11.84 per cent recorded during the preceding week. It has surpassed the peak of 10.54 per cent recorded during the winter influenza season earlier this year. Influenza A (H3) is the predominant circulating strain, accounting for nearly 90 per cent of all detected viruses, followed by influenza A (H1) accounting for nearly 10 per cent. Influenza B accounted for the remainder. The influenza admission rate in public hospitals is 0.64 cases per 10 000 population, which was lower than 0.87 cases recorded in the preceding week. The outbreaks of influenza-like illness (ILI) in schools and residential care homes remained at a high level. As of yesterday (October 29), a total of 693 ILI outbreaks have been reported in schools since the start of the school year in September, including 73 outbreaks in kindergartens/child care centres, 376 outbreaks in primary schools and 244 outbreaks in secondary schools. There have been 16 severe paediatric influenza cases since the start of the school year in September, including one fatal case. The affected children aged from 11 months to 17 years, with 11 having good past health.
"Based on the current level of influenza activity and trend analysis, the local influenza activity is expected to remain at a relatively high level over the next few weeks. Furthermore, viruses tend to become more active when temperatures drop. The winter influenza season in Hong Kong typically occurs between January and March. The current summer influenza season may overlap with the upcoming winter influenza season, which could lead to more hospitalisations due to influenza infection than in previous years. I urge all persons aged six months or above, except those with known contraindications, who have not yet received the SIV, to act promptly, particularly those high-risk groups such as the elderly, children, and adults with underlying illnesses and immunosuppression. Members of the public may also contact their family doctors to arrange for vaccinations," the Controller of the CHP, Dr Edwin Tsui, said.
Members of the public, especially children, the elderly and those with underlying illnesses, should seek medical advice promptly if presented with fever and respiratory symptoms, for early treatment. As children with influenza can deteriorate rapidly, parents must pay close attention to their children's condition. They should go to the Accident and Emergency Department immediately if the child's condition deteriorates, for example if they develop symptoms such as shortness of breath, wheezing, blue lips, chest pain, confusion, a persistent fever or convulsions.
Territory-wide Sewage Surveillance Programme to cover seasonal influenza virus
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Hong Kong has long maintained comprehensive communicable disease surveillance systems to monitor the activity levels of various communicable diseases in Hong Kong. This system includes surveillance of statutory notifiable infectious diseases, sentinel surveillance, outbreak surveillance, laboratory surveillance and sewage surveillance. To further enhance the capability of monitoring seasonal influenza in Hong Kong, the CHP's Territory-wide Sewage Surveillance Programme will include seasonal influenza viruses, aiming to enhance surveillance and early warning capabilities, thereby enabling the timely formulation of public health response measures to better safeguard public health.
"The Territory-wide Sewage Surveillance Programme is a major breakthrough in surveillance of communicable diseases in recent years. During the COVID-19 pandemic, the novel approach of detecting SARS-CoV-2 virus load in sewage became a vital tool for tracking the virus and identifying the source of infection locally. Currently, COVID-19 has become endemic and is managed as a common respiratory disease. The objective of COVID-19 sewage surveillance has shifted from source tracing to routine surveillance of the virus activity in the community," Dr Tsui said.
"The CHP has been exploring ways to optimise the sewage surveillance programme by gradually expanding it to monitor other communicable diseases based on research findings. Since late last year, the CHP has launched a pilot scheme to analyse data on seasonal influenza using collected sewage samples, comparing the results with existing local influenza surveillance trends based on laboratory respiratory specimens. The results showed that the trends of sewage viral load were highly correlated with the percentage of respiratory specimens that tested positive. The results confirmed that sewage surveillance effectively reflects local seasonal influenza activity. Sewage monitoring detects trend changes earlier than the current indicators based on medical institutions, such as clinics, hospitals and clinical laboratories. The relevant results are disseminated through the latest issue of "Communicable Diseases Watch" published today. Building on the success of the pilot scheme, the CHP has regularised this initiative as a supplementary indicator to the traditional influenza surveillance system. Starting this week, the CHP will release weekly monitoring data through the COVID-19 & Flu Express for reference by healthcare professionals and the public," Dr Tsui added.
"The DH will continue to proactively explore the latest scientific developments and applications of sewage surveillance. Based on the local epidemiological situation, the DH will expand the scope of sewage surveillance to include other infectious diseases at an appropriate time, thereby providing comprehensive protection for public health and safeguarding the well-being of the community," Dr Tsui said.
As announced in the 2023 Policy Address, the Government will enhance local capacity in surveillance, early warning, as well as prevention and control of emerging communicable diseases. The Hong Kong Jockey Club has provided funding support. The Territory-wide Sewage Surveillance Programme is part of the abovementioned programmes.
Ends/Thursday, October 30, 2025
Issued at HKT 20:10
Issued at HKT 20:10
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