Two of the newest Covid-19 variants, Mu and Lambda, found in Ireland

WHO adds Mu and Lambda to list of ‘variants of interest’ as 11 cases identified here

Eleven cases of the two newest Covid-19 variants of interest have been identified on the island of Ireland.

While the dominant Delta variant continues to account for more than 90 per cent of sequenced cases on both sides of the Border, six cases of the Mu variant and five of the Lambda variant have been identified.

Last month, the World Health Organisation added Mu, or B.1.621, to its list of "variants of interest" because of preliminary evidence it can evade antibodies.

The variant was first identified in Colombia in January and spread rapidly there.


But while Mu has a number of mutations that suggest it could evade the protection provided by vaccines, to date there is little evidence it actually can.

And while at one point it accounted for 40 per cent of sequenced cases in Colombia, no Mu cases have been detected there in the past month. It has, however, spread to 40 other countries.

Four Mu cases have been sequenced in the Republic and two in Northern Ireland, according to Gisaid, an international consortium for tracking variants.

Peru is the country of origin of another variant, Lambda, which is related to the Alpha variant that was dominant here at the start of this year. As with the other suspect variants, Lambda (also known as C.37) carries a number of mutations that could be problematic, including increased transmissibility and increased resistance to neutralising antibodies.

While there is some evidence Lambda can lead to more severe infection, it doesn’t seem to possess a transmission advantage over the prevailing Delta strain.

It was, however, classified as a variant of interest by the World Health Organisation last June.

Four cases of Lambda have been sequenced in the Republic and one in the North.

Another variant attracting attention is the C.1.2 lineage, after South African authorities issued an alert about it.

This variant has not spread to any great extent, but scientists say it possesses mutations similar to those seen in other variants of interest.

Director of the National Virus Reference Laboratory Dr Cillian De Gascun had said this variant is worth monitoring so that more can be learned about it in relation to transmissibility, disease severity or vaccine effectiveness.

Amino acid changes

He said C.1.2 had a significant number of amino acid changes in the spike protein, many of which have been seen in other variants, and it also appears to have more mutations at this point than might be expected.

So far, the virus has not fulfilled the WHO criteria to qualify as a “variant of concern” or “variant of interest”.

None of the newer variants shows signs so far of being “fitter” than the Delta variant, which is highly transmissible. And while breakthrough infections are occurring, vaccines are highly protective against serious illness caused by all known variants.

Paul Cullen

Paul Cullen

Paul Cullen is Health Editor of The Irish Times