The first cases of a new Covid-19 variant of concern have been detected in the Republic.
Two cases of BA.4, a sublineage of the currently dominant Omicron Covid-19 variant, were detected earlier this month, according to chief medical officer Dr Tony Holohan.
No cases of a related sublineage, BA.5, have as yet been identified here, he says in his latest weekly report on the pandemic.
BA.4 and BA.5 were designated variants of concern by the European Centre for Disease Prevention and Control (ECDC) earlier this month. They were first identified in South Africa in January and February this year, and have gone on to become dominant there.
In the UK, 115 cases of BA.4 and 80 cases of BA.5 have been detected. In Portugal, the two strains have been linked to a recent resurgence of cases there.
Dr Holohan says the two strains have a growth advantage most likely because they can evade immunity provided by prior infection and vaccination, particularly as this wanes over time.
Scientists expect BA.4 and BA.5 will eventually replace the BA.2 sublineage that is dominant in Europe at present.
However, there is no indication they are any more severe than previous Omicron lineages. The ECDC has warned that they may cause increased virus transmission in Europe in the near future.
Dr Holohan, in his May 13th report, says the overall epidemiological situation in Ireland remains broadly positive, "albeit we will need to continue to monitor developments with emerging variants over the coming weeks".
“Although there continues to be high levels of infection and a significant number of cases receiving general hospital care, the numbers of detected infections and hospitalised cases have reduced considerably over recent weeks,” he says.
The hospital system remains under considerable pressure, he notes, with few available beds and with Covid-19 continuing to impact on acute capacity and operational effectiveness in some locations.
There were 214 patients with Covid-19 in hospital on Sunday, down from 231 on Friday. The Sunday figure included 25 in ICU, up from 22 on Friday.
Anthony Staines, professor of health systems at DCU and a member of the Independent Scientific Advocacy Group (ISAG), said it is “not surprising” cases of BA.4 have been detected in Ireland as the variant is very infectious.
“The strength we have here is there is a very high level of vaccination. Some other places that have had significant waves of BA.4 and BA.5 have had less vaccination,” he said.
“The short answer is we don’t know what will happen. We obviously need to keep a sharp eye on it.”
Prof Staines said it was important that people wear masks in crowded places and ensure good air hygiene and ventilation, as well as taking up vaccination, in order to mitigate the risk of another Omicron wave.
As of May 10th, 52 per cent of Covid-19 patients in hospital were there because of the disease. Covid-19 was the primary reason for admission in half of all ICU patients testing positive for the virus.
Last week, more than 34,000 PCR tests for the virus were completed, with a positivity rate of 12.8 per cent.
The Health Protection Surveillance Centre (HPSC), the HSE arm that monitors the progress of the pandemic, de-escalated its emergency response in mid-May, according to Dr Holohan.
Although significant resources remained dedicated to Covid-19, he said, other priority work was being “upscaled” and resources were being diverted to these areas from Covid-19.
As a result, the HPSC will now update its Covid-19 data hub on a weekly rather than a daily basis.