Figures from Public Health England (PHE) show that the consulation rate for flu-like illness has now risen beyond the baseline threshold level in England and Wales - and is now at 'low intensity' level on the scale for measuring an epidemic.
Data published by the RCGP research and surveillance centre show that in England, the consultation rate for influenza-like illness rose from 8.4 per 100,000 in the final week of 2018 to 14.4 in the first week of 2019 - a sharp rise that was mirrored in each region of England.
The consultation rate was the highest in the Midlands and East area at 16.6 per 100,000, and across England cases were highest among patients aged 45 to 64 years old, at 21.7 per 100,000.
PHE warned that the sharp rise in flu cases over the past week should be 'interpreted with caution' because bank holidays could skew figures.
However, with cases now above the baseline threshold in most of England and colder weather expected next week, GP practices could be set for a surge in consultations for flu.
The PHE report highlighted a wider rise in cases of respiratory conditions across general practice in-hours and out-of-hours, and in emergency department attendances.
Asthma consultation rates have also risen and are 'above expected levels', PHE has warned.