Scientists to investigate activity of new ‘Delta Plus’ variant in Ireland

Dr Cillian De Gascun says subvariant is not driving increase in cases in Republic

Irish scientists will start investigating where and what ages the new "Delta Plus" Covid-19 variant is infecting and whether it is causing more severe illness, virologist Cillian De Gascun has said.

The new mutated form of the Delta coronavirus variant – categorised as a “variant under investigation” by the UK health authorities – has been detected in more than 80 cases, he said.

The new AY.4.2 variant accounts for 6 per cent of Covid-19 cases in the UK but is said to be 10 to 15 per cent more transmissible than the Delta variant that is dominant in Ireland and Britain.

There is no evidence yet to suggest that the variant causes greater illness in the people it infects or that it renders the Covid-19 vaccines ineffective but it may have increased case numbers in Britain.


The UK Health Security Authority has said that early evidence suggests that the Delta subvariant may have increased the growth rate in the UK compared to the original Delta variant.

It has not yet been defined as a “variant of concern” – the highest risk category for variants.

Dr De Gascun, director of UCD’s National Virus Reference Laboratory, said the new variant AY.4.2 was “not driving” the increase in the number of Covid-19 cases in the State given that it accounted for less than 2 per cent of the 4,000 cases checked in September.

“It’s important that we monitor these things because a more transmissible virus, if and when it becomes dominant, will lead to more cases, which obviously may impact on admissions to hospitals. It is something we need to monitor but it is natural that the virus would continue to evolve,” said Dr De Gascun, who is a member of the National Public Health Emergency Team.

He said that the UK evidence appears to show that the subvariant has “a modestly increased growth rate” but this was based on “reasonably small numbers” of the variant relative to the 50,000 new coronavirus cases being reported every day in Britain.

“It is still a minority variant in the UK. It is certainly a minority variant here. Will it become dominant? By sheer weight of numbers, if it is more transmissible and if transmission continues to occur, then it will and it’s just a question of how long that will take,” said Dr De Gascun.

The variant did not seem to be increasing transmissibility to the same extent as the Alpha variant, first detected in the UK, did last year or the Delta variant, first found in India, he said.

The Alpha variant that caused Ireland's third wave last January and February, the most severe of the pandemic, was about 50 per cent more transmissible than the original virus that spread from Wuhan in China, while the Delta variant was about 60 per cent more transmissible than that.

Dr De Gascun said scientists would look at where the Delta Plus cases are geographically and the age groups affected along with the disease severity to understand the variant better.

“It is similar to what they will do in the UK but with much smaller numbers overall so it will take longer to reach our conclusions because of the small number of cases we have,” he said.

Simon Carswell

Simon Carswell

Simon Carswell is News Editor of The Irish Times