PEOPLE are being urged to get the flu jab as more are catching the illness earlier than usual this winter.
The Public Health Agency (PHA) warned that flu had started to circulate.
It urged people to receive the vaccine before it spread more widely.
The latest weekly bulletin showed people consulting their GP with flu or flu-like illness had risen sharply.
It was recorded as 29.2 per 100,000 population, compared to 6.0 per 100,000 this time last year.
Some schools have been shut in recent weeks to allow deep cleans to stop the spread of illness.
The PHA urged parents of pre-school pupils "to maximise protection for their children against flu" by getting them the nasal spray vaccine. Those aged 65 and over, under the age of 65 with underlying health conditions, and pregnant women are also more likely to develop serious complications from flu, so should get vaccinated too, it added.
The primary school vaccine programme is once again operating following a temporary pause in ordering the vaccine, caused by manufacturer delays.
Dr Jillian Johnston, Consultant in Health Protection at the PHA, said the vaccine was the best defence.
"The increase in cases is not unusual but we are seeing it earlier than expected," she added.
"Those who do develop flu-like illness can help reduce spreading the infection by maintaining good hand hygiene, covering their mouth or nose when coughing or sneezing, together with appropriate disposal of tissues and staying home when ill with a cough and fever."
