The North's pre-epidemic threshold for flu consultations was breached between Christmas Eve and New Year's Eve, according to new Public Health Agency (PHA) figures published today.
However, the number of flu instances detected in hospitals and labs was down over the period, the agency reported.
Between December 24 and December 31 there was a surge in consultations at GP practices and out-of-hours (OOH) clinics with a growing number of people concerned they may be suffering from the virus.
According to the PHA: "NI GP consultation rates increased slightly from 20.7 per 100,000 population in week 51 to 22.7 per 100, 000 population in week 52, 2017, exceeding the pre-epidemic threshold of 22.58 per 100,000 population. The NI GP consultation rate in week 52 is higher than the same period in 2016/17 (13.7 per 100,000 population)".
There was also a substantial increase in OOH GP consultations for flu between Christmas Eve and New Year's Eve.
The PHA have confirmed that "OOH GP consultation rates for flu/flu-like illness increased substantially rising from 17.9 per 100,000 population in week 51 to 37.2 per 100,000 population in week 52, 2017".
Despite the pre-epidemic threshold for doctors' consultations having been breached the number of actual flu cases detected in hospitals and in labs decreased over the holidays.
"The number of detections of influenza from hospital wards reported to PHA decreased from a total of 112 detections in week 51, to 90 in week 52, 2017.
"There were six cases reported in Intensive Care Units (ICU) with laboratory confirmed influenza in week 52 giving a total of 16 cases this season to date.
"Two deaths were reported in week 52 among ICU patients with laboratory confirmed influenza," the PHA stated, in relation to hospital cases.
As for lab identifications, it said: "The number of positive influenza laboratory detections decreased from 132 in week 51 to 113 in week 52."
So far this winter there have been two detections of swine flu, while the majority of instances have been of the A(H3N2) strain, which is responsible for season flu, every year, and which also inflicted the worst flu season since 2009 on Australia during its winter of 2017.
"At this point in the season there have been a total of 185 detections of influenza A(H3), 100 of influenza B, 100 of influenza A (typing awaited), and two detections of influenza A(H1N1) 2009," the PHA confirmed.