The swine flu has officially returned to Ireland.
The HSE says there has been a significant increase in cases of the H1N1 strain reported at hospitals in recent days.
The increase is due to people returning to work following the Christmas break.
It comes as 541 patients wait on trolleys across the country today, according to the Irish Nurses and Midwives Organisation,
Health Minister Simon Harris is urging people to stay away from hospitals if possible.
"It is not too late to get vaccinated and the good news is that the vaccination is very effective in relation to this strain of flu," said Mr Harris.
"We are entering a challenging period, as we knew we always would. The figures remain better then they were last year and we continue to do all that we possibly can to help the health service and I would again repeat my call to citizens to help support front-line staff by keeping our emergency departments for emergencies."