Two cases of a newly classified Covid-19 variant of concern have been confirmed in Ireland.
On May 12 the European Centre for Disease Prevention and Control reclassified two sub-lineages of the Omicron variant of Covid-19, BA.4 and BA.5, from variants of interest to variants of concern.
In the chief medical officer's latest weekly report on Covid-19 to Health Minister Stephen Donnelly, he says that two cases of BA.4 have been identified as of the week beginning May 7.
Dr Tony Holohan said: "In the context of the international situation in relation to these variants, it should be noted that, as of week 18 2022 (May 7), two cases of BA.4 and no cases of BA.5 have been identified in Ireland.
"ECDC reports that BA.4 and BA.5 were first detected in South Africa in January and February 2022 respectively, and since then they have become the dominant variants there.
"ECDC has indicated that the currently observed growth advantage for BA.4 and BA.5 is likely due to their ability to evade immune protection induced by prior infection and/or vaccination, particularly if this has waned over time."
Dr Holohan added: "There is currently no indication of any change in severity for BA.4/BA.5 compared to previous Omicron lineages.
"With the exception of Portugal and Austria, the proportion of BA.4 and BA.5 in EU/EEA countries is currently very low, although the ECDC has advised that, given the signals of increased growth rate, it is possible that one or both of these sub-lineages may cause increased SARS-CoV-2 transmission in the near future in EU/EEA countries."
The letter, dated May 13, also says that the five-day rolling average of daily PCR-confirmed cases is 610 as of May 12, a 16% decrease from the 729 cases reported on May 5.
The Covid-19 burden on acute hospital care remains "significant", Dr Holohan said, but has "substantially reduced" from a recent peak of more than 1,600 cases in hospital in late March, to 235 as of May 13.
Dr Holohan also said that there "continues to be a significant number of cases of hospital-acquired infection", though the numbers are decreasing steadily.
There were 56 hospital-acquired Covid infections reported in the week ending May 1, compared with 80 in the week ending April 24, and 159 in the week ending April 17.
As of May 10, roughly half of coronavirus-positive cases had been admitted to hospital for Covid-19, while the other half were asymptomatic infectious cases.