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Hong Kong Enters 1st Flu Season In 3 Years

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  • Hong Kong Enters 1st Flu Season In 3 Years

    Hong Kong Enters 1st Flu Season In 3 Years

    HK CHP Influenza Surveillance Data


    Hong Kong is known for frequently seeing a biphasic or `double peaked’ flu season, with their heaviest activity usually occurring between February and April and a less severe season in mid to late summer (see 2014-2018 graphic below).

    A more typical biphasic pattern for Hong Kong

    But due to strict Zero-COVID precautions in place since early 2020, influenza activity has been basically flat-lined for the past 3 years. Now that Hong Kong - like Mainland China - has dropped many of their COVID prevention measures, influenza has been staging a come back.

    Although reports are notoriously sketchy, Mainland China has seen a large resurgence of influenza A (see Chinese Media Reporting Oseltamivir Shortages as Flu Cases Surge) and Guangdong Province has reportedly closed some schools and has issued an influenza alert.

    Today Hong Kong's CHP has published their weekly influenza/COVID epidemiological report, which reports that influenza levels (mostly H1N1) have now exceeded the epidemic threshold level.

    Local Situation of Influenza Activity (as of Apr 5, 2023)
    Reporting period: Mar 26 – Apr 1, 2023 (Week 13) 
    • The latest surveillance data showed that the overall local seasonal influenza activity continued to increase and exceeded the baseline threshold, indicating that Hong Kong has entered influenza season.
    • Influenza can cause serious illnesses in high-risk individuals and even healthy persons. Given that seasonal influenza vaccines are safe and effective, all persons aged 6 months or above except those with known contraindications are recommended to receive influenza vaccine to protect themselves against seasonal influenza and its complications, as well as related hospitalisations and deaths. 
    • As Hong Kong continues to face the challenge of COVID-19 pandemic, influenza viruses and the virus that causes COVID-19 may both spread in the winter influenza season. To protect the healthcare system from being overwhelmed, getting influenza vaccination is therefore important. For the 2022-23 season, Seasonal Influenza Vaccination School Outreach and the Residential Care Home Vaccination Programme were launched on September 29, 2022, whereas the Vaccination Subsidy Scheme (VSS) and the Government Vaccination Programme (GVP) began on October 6, 2022. For details, please refer to the webpage ( 
    • Apart from getting influenza vaccination, members of the public should always maintain good personal and environmental hygiene.
    • The current influenza surveillance data should be interpreted with caution as the ongoing COVID-19 pandemic has influenced the monitoring systems.

    Hong Kong's CHP also issued the following statement today:

    Hong Kong enters influenza season

    The Centre for Health Protection (CHP) of the Department of Health today (April 6) announced that according to the latest surveillance data, local seasonal influenza activity has continued to increase in the past week and exceeded the baseline thresholds, indicating that Hong Kong has entered the influenza season. All sectors of the community should heighten their vigilance and enhance personal protection measures against influenza.

    From the latest surveillance data, among the respiratory specimens, the weekly percentage of detections tested positive for seasonal influenza viruses has increased from below 1 per cent in the first week of March to 9.89 per cent in the week ending April 1. The majority of positive detections in that period were influenza A(H1) (around 77 per cent) and A(H3) (around 21 per cent), with very low influenza B activity. Of note, past epidemiological data showed that children and adults aged from 50 to 64 years were relatively more affected in seasons dominated by influenza A(H1).

    The overall admission rate with principal diagnosis of influenza in public hospitals has also continued its rising trend, from 0.01 per 10 000 population in the first week of March to 0.25 per 10 000 population in the week ending April 1. Separately, in early and mid-March, there were one to two institutional influenza-like illness outbreaks reported to the CHP per week, while there were 12 outbreaks reported in the week ending April 1, affecting 49 persons. The 12 outbreaks included five in primary schools, one in a secondary school, two in residential care homes for the elderly, one in a residential care home for persons with disabilities, two in special schools and one in a hospital.

    "Given that local seasonal influenza activity has been staying at low levels over the past three years, the immunity against influenza in the local community as a whole may be relatively weaker than in the past. We urge the public, particularly children, the elderly and chronic disease patients, to receive seasonal influenza vaccination (SIV) as early as possible. Strict personal, hand and environmental hygiene should also be observed at all times. Those who have plans to travel abroad during the Easter holidays are also reminded to pay special attention to the influenza situations of their travel destinations before departure and strengthen personal protection," a spokesman for the CHP said.

    The CHP will issue letters to doctors, hospitals, institutions and schools to appeal for heightened vigilance and appropriate actions. To prevent transmission of influenza in school environments, schools are reminded to take additional measures, including actively checking the body temperature of all students every day when they arrive at school to identify those with fever. Those with fever, regardless of having respiratory symptoms or not, should not attend school. In addition, staff of schools and institutions should be alert to their own conditions every day and should refrain from work if they have fever or respiratory symptoms. Schools should promptly make a report to the CHP in the case of an increase in fever or respiratory illnesses or absenteeism for epidemiological investigations.

    The spokesman reminded the public that the Government has rolled out in phases various SIV programmes since September last year to provide eligible members of the public with free or subsidised SIV. Since SIV is one of the effective means to prevent seasonal influenza and its complications, as well as reduce influenza-related hospitalisation and death, all persons aged 6 months or above, except those with known contraindications, are recommended to receive SIV for personal protection. As it takes about two weeks to develop antibodies, members of the public, particularly persons at higher risk of getting influenza and its complications, including the elderly and children, should receive SIV early.

    As of April 2, about 1.53 million doses of SIV had been administered via the Government Vaccination Programme, the Vaccination Subsidy Scheme (VSS) and the Seasonal Influenza Vaccination School Outreach (Free of Charge) Programme 2022/23, representing a roughly 24 per cent rise over the same period in 2021/22 season. The influenza vaccination coverage rate for the elderly aged 65 or above was about 47 per cent whereas that for toddlers and adolescents aged 6 months to below 18 years was about 40 per cent, indicating that most people in different age groups have yet to receive SIV. The spokesman appealed to members of the public to get the vaccination for protection.

    Meanwhile, a slight increase has been observed recently on the positive nucleic acid test laboratory detections newly recorded for COVID-19 as well as per capita viral load in relation to COVID-19 from sewage surveillance. Although the number of severe illness cases and death cases of COVID-19 remains relatively stable, the spokesman urged the public to complete the recommended dosage of COVID-19 vaccines and SIV as early as possible for better protection since a person who gets influenza and COVID-19 at the same time may be more seriously ill and would have a higher risk of death.

    The public should also maintain good personal and environmental hygiene against influenza and other respiratory illnesses and note the following:
    • Surgical masks can prevent transmission of respiratory viruses from ill persons. It is essential for persons who are symptomatic (even if having mild symptoms) to wear a surgical mask;
    • For high-risk persons (e.g. persons with underlying medical conditions or persons who are immunocompromised), wear a surgical mask when taking public transport or staying in crowded places. It is important to wear a mask properly, including performing hand hygiene before wearing and after removing a mask;
    • Avoid touching one's eyes, mouth and nose;
    • 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 mouth and nose with tissue paper when sneezing or coughing. Dispose of soiled tissue paper properly into a lidded rubbish bin, and wash hands thoroughly afterwards;
    • Maintain good indoor ventilation;
    • When having respiratory symptoms, wear a surgical mask, refrain from work or attending classes at school, avoid going to crowded places and seek medical advice promptly; and
    • Maintain a balanced diet, perform physical activwithity regularly, take adequate rest, do not smoke and avoid overstress.
    For the latest information on influenza activity, please visit the CHP's influenza pageand COVID-19 & Flu Express. As for vaccination, the public may visit the CHP'sVaccination Schemes page.

    Ends/Thursday, April 6, 2023
    Issued at HKT 19:30

    While there are still some who doubt that the public wearing of face masks protects against respiratory infections, the Hong Kong government lifted all mandatory mask-wearing requirements(effective March 1st), and just 36 days later they have their first influenza epidemic in 3 years.

    Which is why I keep a stash of N95s in my closet, for when the next respiratory virus threatens.
    All medical discussions are for educational purposes. I am not a doctor, just a retired paramedic. Nothing I post should be construed as specific medical advice. If you have a medical problem, see your physician.