The highly transmissible BA.2 variant of Covid-19 accounts for almost 95 per cent of virus infections in Ireland, latest figures show.
The spread of BA.2 infections to the near-exclusion of other variants has coincided with the rise in cases in the latest wave of the pandemic, data provided by the Department of Health shows.
BA.2 accounted for just 4 per cent of cases in the third week of January, when most Covid-19 restrictions were lifted by the Government. By the end of February, when the remaining restrictions were removed, it accounted for 76 per cent of cases.
Since then, its dominance has become even more pronounced; in mid-March it accounted for 90.6 per cent of cases and on March 20th, the most recent day for which data is available, 94 per cent.
Over this period, Ireland has experienced a sixth wave of cases, driven by the lifting of restrictions and the spread of BA.2.
The Department’s figures are estimates, culled from the results of PCR tests. BA.2 cases test positive for three gene targets whereas other Omicron sub-lineages - the originally dominant BA.1, BA.1.1 and BA.3 - test negative for one of the targets.
Although the Delta variant, which was dominant here late last year, also tests positive for the three targets it is no longer found here. As a result, a PCR test with a positive S gene target along with two other positive targets is “highly likely” to be infected with BA.2, according to the Department.
Genomic sequencing is required to confirm the presence of BA.2 but this is carried out in under 5 per cent of cases. In addition, sequencing takes a number of weeks to complete, so up to date figures are not available.
However, the results of sequencing carried out by the National Virus Reference Laboratory shows a similar trend of BA.2 ascendancy. In the first week of the year, just one BA.2 case was identified out of 1,978 cases sequenced. By the end of February, the subvariant accounted for 112 cases out of 175 sequenced (64 per cent).
The number of Delta variant cases that were sequenced fell from 73 in the first week of 2022 to one in the third week of February and none the following week.
British authorities last week suggested a "recombinant" strain of Covid-19 involving a mix of BA.1 and BA.2 is growing 10 per cent faster than BA.2. Two recombinants that mix Delta and BA.1 are also being monitored; one, first identified in Cyprus and France, has been given the nickname "deltacron".
Meanwhile, the European Medicines Agency has authorised Evusheld, a combination of the two long acting antibodies tixagevimab and cilgavimab, for Covid-19 prevention.
The treatment, which can be administered in a GP surgery or in the community rather than being given intravenously in hospital, is expected to be used to protect immunocompromised patients.