A county's health officials have warned more children and young people could become infected with a severe strain of flu than usual at this time of year.
Public health bosses in Hertfordshire said hospital admissions were low at the moment but were expected to rise over the next few weeks.
They advised anyone with symptoms to wear a face mask and avoid contact with other people.
The county council's executive member for public health, Ajanta Hilton, has called for a national awareness campaign.
Experts in Hertfordshire and across the country were watching the situation in Australia with growing alarm.
The southern hemisphere country has seen its worst flu season on record, with 1,544 cases per 100,000 people - a 10.8% increase on the 2024 record.
Hertfordshire's director of public health, Sarah Perman, said: "Australia experiences its flu season a few months before we do [and] we're beginning to see with some concern that case rates are rising in this country."
Cases among the under-5s in Australia accounted for almost 11% of all infections (more than More than 44,500 cases) and more than a third of the infections were recorded in children below the age of 15.
Ms Perman said a similar trend was now being seen in the UK, but other groups were also at risk.
Ms Perman added: "We are seeing the dominant virus being a strain of influenza A, which is associated with more severe illness and higher mortality, particularly in older people, than some of the other viruses that we commonly see during the flu season."
She urged children, older people, pregnant women and people with certain health conditions to take advantage of a free vaccination.
"It is also really important," she added, "that as many people as possible who may not be eligible for the free vaccination get their own vaccination, and you can purchase it privately at many pharmacies across Hertfordshire."
The most common symptoms are fever, chills, headache, aching joints and extreme tiredness.
Ms Perman said anyone with these symptoms should "try to limit your contact with others, especially those who might be more vulnerable."
People with symptoms who need to leave the house "should wear a face mask where possible, wash your hands regularly and use dispose of tissues hygienically."
Hilton said: "What I would love to see is a national campaign to really promote the message, coming alongside our local one that goes out to all our GPs surgeries.