As many as 1 in 10 people in Ireland were infected with Covid-19 in 7 day period
Case numbers increased by 363% since the middle of December.
Anywhere between 1 in 10 and 1 in 20 people in Ireland were infected with Covid over the Christmas period.
The information was published in a letter written by Chief Medical Officer Dr Tony Holohan to Minister for Health Stephen Donnelly last Thursday (6 January).
"Given the 7-day cumulative incidence of 2,876 per 100,000, allowing for constraints on testing and undetected infections, the likely population prevalence of active SARS-CoV-2 infection is 5.7%- 9.6%; between 1 in 10 and 1 in 20 of the population are likely to be infected," Dr Holohan wrote.
The letter from the Chief Medical Officer also reveals that in the two weeks of Christmas holidays, 79% of all cases reported were in people aged under 45.
"From 29 December 2021 – 4 January 2022, there have been approximately 272,308 laboratory tests reported in community, private, and acute laboratories," Dr Holohan added.
"The 7-day test positivity rate in the community has significantly increased from 17.4% at the last NPHET meeting (14 December 2021) to 60.5%."
As of 4 January, the Omicron variant accounted for 96% of all new positive cases reported.
NPHET is recommending that while medical grade masks are not suggested on a national level, that medically vulnerable people and people over the age of 60 should wear them " in crowded outdoor spaces or confined indoor spaces, including on public transport and in retail and healthcare settings."
"In summary, the overall epidemiological situation in Ireland continues to give rise for concern, noting however, some initial positive indications in terms of markers of disease severity which will continue to be closely monitored over the coming days and weeks," wrote Dr Holohan.
NPHET is set to meet again on 20 January to further discuss the coming weeks and months of living with Covid, including how best to deal with the Omicron variant.
The Government is currently considering the easing of rules surrounding close contacts.
Last week, the European Centre for Disease Prevention and Control (ECDC) updated its guidance regarding isolation for close contacts in response to the rapid spread of Omicron in the European Union.
Though its overall guidance in the area remained unchanged, it said that it was proposing recommendations that can be adapted by EU and EEA Member States when "there is high pressure on healthcare systems and other functions in society," such as from staff shortages due to Covid.