A number of hospitals have been closed to visitors over fears of spreading influenza.
Mercy University Hospital in Cork has been closed to visitors since Friday evening.
The hospital says this is "due to the prevalence of flu".
The restriction is in place until further notice, management adds.
However exceptions will be made "in exceptional cases".
While Cork University Hospital also has visiting restrictions in place to prevent the spread of flu.
All visitors there have been asked to contact the hospital before attending.
On Friday, Dublin's Mater Hospital asked people not to come and visit the hospital unless absolutely necessary.
Children under the age of 12 are not permitted to visit the hospital under any circumstances.
It comes after recent statistics from the Health Protection Surveillance Centre (HPSC) indicated that influenza activity increased in Ireland in December.
It said influenza-like illness (ILI) rates rose to 57.9/100,000 population during week 50 of 2019.
Influenza A (known as H3N2) was the predominant influenza virus, with influenza activity expected to increase over the coming weeks.
During week 50 of 2019, it increased in all age groups - except in persons aged 65 years and older.
The number of influenza hospitalisations also increased, with the highest hospitalisation rates seen in those aged under five.
To date, 627 hospitalised confirmed influenza cases have been reported to the HPSC - the majority due to influenza A.
Twenty-five confirmed flu cases have been admitted to critical care units.
While 17 influenza outbreaks and eight influenza-associated deaths have been reported to HPSC to date this season.
The majority of the deaths are in those aged 65 years and older.
The Health Service Executive (HSE) is also asking people to observe good hand hygiene - by washing hands regularly, using alcohol gels provided in healthcare facilities.
They should also use a tissue to cough or sneeze into, dispose of it immediately afterwards and wash their hands regularly.
It says all visitors to healthcare facilities should check with the facility in advance of visiting.