First cases of ‘concerning’ new Covid-19 subvariant detected in Ireland

XBB.1.5 strain became dominant in US in space of a month but there is no evidence it is more lethal

The first cases of a new Covid-19 subvariant which is causing concern internationally have been detected in Ireland.

The Health Protection Surveillance Centre says “less than five” cases of the XBB.1.5 subvariant were detected by genomic sequencing in the four weeks before Christmas.

This was 0.1 per cent of all sequenced cases in the period.

XBB.1.5, the latest offshoot of the Omicron variant of Covid, became dominant in the US last month and has been detected in more than 25 countries, according to the World Health Organisation (WHO).


XBB.1.5 went from being present in 4 per cent of sequenced samples in the US to 40 per cent just weeks later.

It is expected to also become dominant in Europe. It is highly transmissible and immune evasive, but there is no evidence so far that it is more lethal.

The rise of the new subvariant is expected to lead to more hospitalisations but most people can protect against serious infection through vaccination.

The WHO has expressed concern about the new subvariant. Chief epidemiologist Maria Van Kerkhove said last week XBB.1.5 is the most transmissible Omicron sub-variant that has been detected so far. It spreads rapidly because of additional mutations that allow it to adhere to cells and replicate easily.

According to the European Centre for Disease Control, XBB.1.5 is currently estimated to have a large growth advantage over previously circulating lineages, although there is uncertainty around these estimates.

It said the sub-variant may have an increasing effect on the number of Covid cases in the EU, “but not within the coming month as the variant is currently only present at very low levels in the EU”.

Dr Van Kerkhove warned that the world’s recorded Covid deaths had risen 15 per cent in the last month. “We know that is an underestimate,” she said.

“We do expect further waves of infection around the world, but that doesn’t have to translate into further waves of death because our countermeasures continue to work,” said Dr Van Kerkhove, referring to vaccines and treatments.

Paul Cullen

Paul Cullen

Paul Cullen is a former heath editor of The Irish Times.