The UK Health Security Agency (UKHSA) said cases are rising quickly among children and young people, and are expected to spread to older groups soon.
Officials urged everyone eligible for the flu vaccine to get protected as soon as possible, warning the virus could peak before many vulnerable people are immunised.
Dr Suzanna McDonald from UKHSA said: “Flu has started to circulate a little earlier than usual. It’s a serious disease, not just a bad cold.”
She said early cases are mainly among students and school children but are likely to spread through communities in the coming weeks.
Dr Alex Allen, consultant epidemiologist at UKHSA, said everyone aged 65 and over, pregnant women and those with long-term conditions should book their free NHS flu jab.
“The vaccine is our best defence,” he said, also reminding parents to return school consent forms so children can receive the nasal spray vaccine.
People with flu or Covid symptoms are advised to minimise contact with others, wear a face covering if going out, and keep rooms well ventilated.
UKHSA said Covid levels are currently low and continuing to fall.
Photo: a flu shot being administered
Photo Credit: LuAnn Hunt / Pixabay