People are being 'strongly advised' to wear masks on all public transport as COVID-19 and flu cases rise.
Chief Medical Officer Professor Breda Smyth has said people should also be wearing masks in crowded and confined spaces.
In a pre-recorded video message on Twitter on Monday, Prof Smyth said people should be protecting each other.
"COVID is still with us, and we are not wearing our masks," she said.
"With other respiratory viruses circulating, it is strongly advised that you wear a mask on public transport - and also consider wearing one in crowded and confined spaces.
"Your mask should fit well and cover your nose.
Don't touch it or pull it down over your chin.
"Masking up means that you are less likely to transmit infectious droplets to others.
"Remember: wearing a mask isn't just for you - it's for everyone.
"So please, let's all mask up for each other," she added.
Many of us are on the move at this time of year, catching up with family and friends. Please remember to wear your mask on public transport and in crowded places, to help reduce the spread of COVID-19 and other respiratory viruses. #COVID19 pic.twitter.com/2obt1afMqk
— Chief Medical Officer (@CMOIreland) December 26, 2022
The latest figures show, as of 8am on Monday, there were 656 confirmed COVID-19 cases in hospital with 29 people in ICU.
That compares to just 430 cases in hospital, and 11 in ICU, 14 days ago.
It comes as the Government is said to be considering re-introducing a mask mandate.
Last week the HSE's vaccination lead Eileen Wheelan said there had been a "sharp increase" in people catching COVID and flu since early December.
"The two previous winters, COVID was the dominant virus that was out there; prior to that, the influenza virus was the dominant virus,” she told The Pat Kenny Show.
"But this year, we’re actually seeing an interplay between both the influenza virus and the COVID virus."
A National Crisis Management Team has been set up and Taoiseach Leo Varadkar is due to meet Health Minister Stephen Donnelly to discuss whether masks should be compulsory on public transport again.