The Delta variant of COVID-19 will 'almost certainly' be dominant in Ireland in two weeks' time, according to the director of the National Virus Reference Laboratory.
Up to 55% of cases here last week involved this strain.
Dr Cillian De Gascun says the Delta variant, first discovered in India, is at least twice as transmissible as the COVID-19 strain we experienced last summer.
He says there has been a "dramatic increase" in the proportion of cases identified as Delta here over the past two weeks.
It made up less than 9% of cases between June 7th and 13th - but Dr Gascun says this rose to up to 55% last week.
Last week's figure will be confirmed by further analysis in laboratories.
Dr De Gascun said the current situation will almost certainly mean 'Delta dominance' by the middle of July - leading to an increase in case numbers, hospitalisations and deaths in the following weeks.
Firstly, based on available evidence, the Delta variant appears to be between 40% and 60% more transmissible than the Alpha variant, which has been dominant in Ireland for the last 5 months 2/n
— Cillian De Gascun (@CillianDeGascun) June 29, 2021
He said the Delta variant is already dominant in the UK, accounting for about 97% of cases - with case numbers, hospitalisations and deaths increasing in recent weeks.
Concerns over the variant have led to the reopening of indoor dining being delayed here by at least two weeks.
Dr De Gascun stressed that Ireland now has "very effective" vaccines, a major difference compared to the situation Ireland was facing this time last year.
He said it's key people following the usual public health advice - including social distancing and mask-wearing - while the vaccines roll out and take effect.