Issued by: UK Health Security Agency

Flu positivity jumps to 17.1% as vaccine take-up rates lag behind levels needed to protect the NHS and levels of norovirus highest in a decade for the time of year.

The government’s medical experts are calling on eligible groups to ensure they book their flu and COVID-19 vaccinations before the deadline on 19 December. People are urged to protect themselves before Christmas amid a recent rise in flu cases.

The latest edition of the UK Health Security Agency’s (UKHSA) COVID-19, influenza (flu), Respiratory Syncytial Virus (RSV) and norovirus surveillance bulletin (formally Weekly Winter Briefing) (https://www.gov.uk/government/news/flu-and-covid-19-surveillance-report-published) shows that flu positivity in week 49 jumped to 17.1%, compared to 11.6% in the previous week.

Hospitalisations as a result of flu also rose to 5.53 per 100,000 this week, compared with 3.98 per 100,000 in the previous week’s report.

The national booking system for flu vaccination closes on 19 December and with NHS hospitals already managing record flu levels going into winter, top doctors, including the Chief Medical Officer Professor Chris Whitty, are urging those who are still eligible for vaccination to book their appointments immediately. After this date people will only be able to access the flu vaccine through their GPs and some pharmacies.

The latest figures come as flu and COVID-19 vaccination uptake rates are still not at the levels we need to prevent further rises in admissions. Vaccine uptake currently stands at 37% for those in a clinical risk group.

Alongside increases in cases and hospitalisation due to flu, the latest surveillance data shows that current laboratory reports of norovirus are more than double the 5-season average (1). This is the highest number of cases recorded between week 47 and 48 (747 laboratory reports) in a decade - since the data began reporting in this way in 2014.

Norovirus has increased in all regions across England and all age groups, most notably in those aged over 65. This season the increase in reporting has begun earlier than usual, with activity between 18 November and 1 December 33.2% higher than the previous 2-week period.

Susan Hopkins, Chief Medical Advisor at UKHSA, said:

"The threat of an early flu season is materialising, alongside norovirus rates increasing rapidly. With winter vaccine uptake not yet reaching the high levels we aim for in some eligible groups - including healthcare workers, our forecasts for infection rates are not getting any brighter.

"It is vital that those eligible take up the free flu and COVID-19 vaccines before Christmas. In just one week it will be too late to book through the NHS online booking service. Taking up the vaccine will prevent putting your seasonal plans in jeopardy – and more importantly, prevent the risk of severe illness and hospitalisation.

"The elderly and those with weakened immune systems are most at risk of suffering more serious illness from flu or norovirus, so if you have flu-like symptoms or diarrhoea or vomiting, avoid visiting people in hospital and care homes to prevent passing on the infection in these settings."

Professor Chris Whitty, Chief Medical Officer said:

"The latest data is clear that flu is rising rapidly, and we are approaching a serious flu wave.

"Flu can be unpleasant for many and life threatening for some. With the festive season approaching we can still reduce illness, hospitalisations and deaths by increasing vaccination rates – it is our best defence. Now is the time to get vaccinated if you are eligible."

Several factors are likely contributing to the unusually high levels of norovirus activity we are seeing at the stage of the season, including changes in diagnostic testing.

However, it is most likely that the emergence of an unusual norovirus genotype, GII.17 is driving the increases. This genotype has become the most commonly detected in England since April 2024, accounting for 63.2% of characterised samples during the 2024/25 season to date.

Previously, GII.4 noroviruses have dominated globally with GII.4/Sydney/2012 variants persisting as the most frequently detected variant worldwide since the winter of 2012. There’s currently no indication that GII.17 causes more severe illness, but work is underway to conduct further assessment of severity.

To reduce the spread of norovirus (https://www.gov.uk/government/publications/stop-norovirus-spreading-this-winter-leaflet/how-to-stop-norovirus-spreading), wash your hands thoroughly with soap and warm water, as alcohol-based hand sanitisers are not effective against the virus. Stay at home for at least 48 hours after symptoms stop and disinfect surfaces using a bleach-based cleaner where possible.

The UKHSA COVID-19, influenza (flu), RSV and norovirus surveillance bulletin also showed a slight decrease in RSV cases, while COVID-19 continued to circulate at low levels.

Vaccination against RSV is being offered for the first time this year to anyone who is 28 or more weeks pregnant, along with people aged 75 to 79 years.

The NHS website (https://www.nhs.uk/conditions/norovirus) has information on symptoms, how to help yourself feel better at home, and when to seek medical attention.

The week 50 flu, COVID-19 and RSV surveillance report (https://www.gov.uk/government/statistics/national-flu-and-covid-19-surveillance-reports-2024-to-2025-season/national-flu-and-covid-19-surveillance-report-12-december-week-50) and norovirus surveillance report (https://www.gov.uk/government/statistics/national-norovirus-and-rotavirus-surveillance-reports-2024-to-2025-season/national-norovirus-and-rotavirus-report-week-50-report-data-to-week-48-1-december-2024) have been published.

Notes

(1) The 5-season average for norovirus is calculated from the same period during the 5 seasons of 2016/2017, 2017/2018, 2018/2019, 2022/2023 and 2023/2024, excluding years impacted by the COVID-19 pandemic.

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