The H3N2 subtype triggered two and a half times the normal number of cases in Australia.
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The figure has raised at a steady level week-on-week since October.
Nick Phin, of PHE, said: 'Flu activity, as measured by a number of different systems, has continued to increase in the last week or two.
The Red Cross branded the situation a 'humanitarian crisis' - a term used to describe the devastating civil war in Syria and Yemen.
One includes the so-called 'Aussie flu', a strain of influenza A which wreaked havoc on hospitals in Australia during the country's winter.
According to the NHS, symptoms for flu can include an aching body, exhaustion, loss of appetite, sudden fevers, nausea and headaches.