The Office of the Chief Medical Officer, Professor Breda Smyth, has said that the latest analysis of all registered deaths here, shows that excess pneumonia and influenza mortality was seen in December and January.
During a three-week period in December and January last, there was excess all-cause mortality among those aged 75-84 years of age.
The Chief Medical Officer noted that influenza activity was at very high levels in Ireland during December and early to mid January this year, with a high number of influenza hospitalisations reported.
The details have been provided in response to a written query to the Department of Health, by Stephen McMahon of the Irish Patients Association.
In the correspondence, the CMO's office said that other important factors may affect excess mortality, including the ongoing Covid-19 pandemic, the circulation of other respiratory viruses, the effects of cold weather, and an ageing population.
Health officials say the data is provisional due to the time lag with death registration in Ireland.
Excess mortality refers to the number of deaths from all causes, during a period of time, above and beyond what would normally be expected.
The CMO's office said it is important to note that excess mortality has been seen before, when influenza viruses circulated at high levels in Ireland.
It cited winter 2017/2018 which was characterised as a severe flu season.
It added that the HSE's Health Protection Surveillance Centre anticipates that when further deaths are registered over the coming weeks, further excess mortality for the 2022/2023 winter period will be observed.
It expects that this excess mortality will be seen for at least a four to five week period in December 2022 and January this year.
The office added that excess mortality has also been observed in other European countries, over the course of this winter.
The Central Statistics Office (CSO) publishes official statistics on deaths in Ireland and issues quarterly and yearly statistics on registered deaths.
The latest published deaths data is for Quarter 2 2022 and is provisional.
Provisional data for Quarter 3 2022 will be published in March and for Quarter 4 2022 in June.
The Office of the Chief Medical Officer said this will include data on cause of death and allow more detailed analysis of mortality trends in the period.
