The Centre for Health Protection (CHP) of the Department of Health (DH) today (November 12) recorded a severe paediatric influenza infection case. The CHP once again urged schools and parents to promptly arrange for schoolchildren to receive free seasonal influenza vaccination (SIV). Regarding the recent antigenic drifted influenza A (H3N2) virus strain in Hong Kong and overseas due to genetic mutation, the CHP emphasised that the currently used SIV remains effective against this antigenically drifted strain. The SIV is still one of the most effective methods to prevent influenza and its complications, and can reduce the risk of serious complications or death from infection.
 
Latest severe paediatric influenza infection case
----------------------------------------------------------
 
     The case involves an 11-year-old boy with good past health. He has developed a fever and cough with sputum since November 7, and his symptoms persisted. On November 10, he developed dizziness and attended a private hospital. He was admitted for treatment and is currently in serious condition. His nasopharyngeal swab specimen tested positive for influenza A virus upon laboratory testing. The clinical diagnosis was influenza A infection complicated with shock.

     He has not received the 2025/26 SIV and had no travel history recently. His household contacts have no influenza-like illness (ILI) symptoms so far.
      
     Preliminary investigations revealed that the boy joined a overnight camp organised by his school between November 3 and 7. Nine schoolmates from the same grade developed ILI symptoms between November 6 and 11. Seven of them tested positive for influenza A using rapid antigen tests. All of them had mild symptoms and did not require hospitalisation. The CHP staff inspected the school and advised the school to implement the necessary infection control measures. It will be put under medical surveillance.
      
     Including the above case, 18 severe influenza cases involving children have been recorded so far this summer influenza season, including one fatal case. Among the nine cases recorded since the launch of this year's SIV Programmes, only one had received this year's SIV within four days prior to onset of illness. As it generally takes two weeks for the body to develop sufficient protection after vaccination, that case was not protected by the vaccine.
 
SIV also provides protection against the influenza A (H3N2) antigenic drift virus
-----------------------------------------------------------------------------------------

     "This year, the influenza season has arrived earlier than usual in many regions worldwide, including Japan, Republic of Korea and the United Kingdom. Hong Kong's summer influenza season started later than usual this year and is still ongoing. Furthermore, a genetically mutated influenza A (H3N2) virus strain has recently emerged in Hong Kong and many other regions. However, there is currently no evidence that this strain causes more severe illness," the Controller of the CHP, Dr Edwin Tsui, said.
      
     "Seasonal influenza viruses undergo genetic changes from time to time, giving rise to new subclades. If key genes mutate, it may lead to antigenic drift, which is expected and occurs periodically. Therefore, the World Health Organization (WHO) and National Influenza Centres in different regions (including the Public Health Laboratory Services Branch of the CHP, Hong Kong SAR, China) continuously monitor the prevalence and evolution of seasonal influenza viruses. Each year, the WHO recommends the virus strains to be included in the next season's SIV based on viral analysis data. It is worth noting that influenza vaccines provide a certain degree of cross-protection against different but related virus strains," he explained.
      
     "According to the announcement made by the UK Health Security Agency (UKHSA) yesterday (November 11), the latest local data showed that over 80 per cent of laboratory confirmed influenza patients were infected with the influenza A (H3N2) subtype. Local authorities' research also found that despite antigenic drift in the currently circulating influenza A (H3N2) virus, this season's SIV remains effective in preventing hospitalisation among children aged two to 17 years old, with an effectiveness of 75 per cent, and among adults, the effectiveness stands at 40 per cent. These results demonstrate that the SIV continues to provide adequate protection for the general public, particularly children, significantly reducing the risk of hospitalisation. Therefore, I urge all persons aged six months or above who have not yet received the SIV to do so promptly, except those with known contraindications. High-risk groups such as the elderly, children, and adults with underlying illnesses and immunosuppression should receive the SIV immediately. Apart from participating in the various SIV Programmes launched by the Government, members of the public may also contact their family doctors to arrange vaccinations," Dr Tsui added.
      
     According to the latest surveillance data, influenza activity began to decline in the last week of October, but remains at a relatively high level. However, as the weather turns cooler, influenza activity may still fluctuate. Based on past experience, Hong Kong's winter influenza season typically occurs between January and March. Therefore, it is not ruled out that a winter influenza season may occur early next year.
      
     "With declining influenza activity and many schools having held SIV school outreach activities, reported school influenza outbreaks have significantly decreased recently. The number of school outbreaks fell from the peak of 169 cases in mid-October to 61 cases last week. Since the start of the school year, about 1 700 schools have conducted school outreach activities, which is higher than the about 1 400 schools compared to the same period in the last season. In addition, 2 220 schools (96 per cent) have scheduled to carry out the outreach activities by the end of this month. I hope all sectors of the society could join hands in appealing parents to arrange SIV for their children, while also educating parents on the importance of vaccination. This will promote a greater vaccine uptake among young children, increased vaccination coverage rate and strengthen protection for children," Dr Tsui said.
      
     Dr Tsui also reminded high-risk individuals to wear surgical masks when staying in crowded places. People with respiratory symptoms, even if mild, should wear a surgical mask and seek medical advice promptly. They should also consider whether to attend work or school. 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 an 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.
   
     Members of the public can visit the CHP's seasonal influenza and COVID-19 & Flu Express webpages for more information.

Ends/Wednesday, November 12, 2025
Issued at HKT 22:43

NNNN