The Department of Health said people should remain vigilant
An adult with swine flu died in Northern Ireland over Christmas.
It is not known whether the deceased was a man or a woman. The death was announced in the Department of Health's weekly swine flu update.
To date, 19 people from Northern Ireland who had swine flu have died. Seventeen of them died in NI, one in England and one in Spain.
Deputy Chief Medical Officer Dr Elizabeth Mitchell said there had been a decrease in swine flu detections.
In the bulletin, she said that while cases of swine flu were decreasing, other respiratory viruses were circulating.
In particular, there has been an increase in detections of Respiratory Syncytial Virus (RSV) which can cause flu-like symptoms.
"Swine flu has now been circulating within Northern Ireland since May 2009," Dr Mitchell said.
"We have seen two waves of infection from the virus and our planning and preparation has meant that the likelihood of a further wave has been significantly reduced.
"This is due in part to the extent in which the virus has already circulated in the community, and also as a result of the very successful vaccination programme in Northern Ireland.
"We know from experience of previous pandemics that flu viruses can be unpredictable so we can not completely rule out the possibility of a further wave.
"We will therefore continue to monitor the situation carefully and adapt our plans accordingly. The vaccine remains the best way to be protected against swine flu."