Flu season is ‘officially underway’ say health officials after a sudden and significant rise in cases.

Anyone eligible for a flu vaccine who has yet to come forward is being encouraged to do so after a notable increase, says the UK Health Security Agency, in the number of people confirmed to have caught the virus.

Data also shows an increase in the number of people seeking emergency treatment in A&E for flu as well as a subsequent rise in hospital admissions.

An average of 400 patients were in hospital each day last week with the infection – up from 240 the previous week. The numbers needing critical care beds is also rising – with 35 new admissions between December 4 and December 10.

Influenza positivity rates overall have also climbed from 2.4% to 5.6% in the last week.

Dr Mary Ramsay, Director for Immunisation and Programmes at UKHSA, explained: “Flu levels are on the rise, so get your vaccine now to make sure that you are winter strong, and before pharmacies and surgeries begin to close for the Christmas period.”

So far this year, flu vaccine uptake in eligible groups is similar to the last couple of years – although the UKHSA says there is a ‘particular need’ for pre-schoolers, pregnant women and those in health and social care workforces to take up the offer.

Children aged two and three are eligible for the nasal spray, which can be given via their child’s GP surgery.

Because of the increased levels of flu now circulating, the UKHSA has recommended that antiviral medicines are now also prescribed for community-based cases.

Those eligible for antiviral prescriptions if they have flu, include patients in clinical at-risk groups as well as any who are at risk of severe illness and complications from flu if not treated. This also includes people who present with the symptoms of flu and those who have been exposed to flu-like illnesses from someone they live with, including residents of care homes.

The country’s Chief Medical Officer and Chief Pharmaceutical Officer have issued an alert to the NHS, says the government, notifying the healthcare system that antiviral medicines can now be prescribed and supplied for cases of flu identified outside of hospitals.

Dr Ramsay added: “Flu antivirals are effective in helping to keep people out of hospital and preventing the virus spreading to other more vulnerable household and family members.

“Now that we are seeing flu increasing it’s important that GPs consider the possibility of flu in respiratory patients and the use of antivirals in line with national guidance, particularly if they have ruled out Covid-19.”