Explained: The new XEC Covid-19 variant – and why a summer wave is likely

Another Covid-19 wave is likely this summer, a modeller says, as a new mutant coronavirus variant emerges overseas. Experts tell Jamie Morton what Kiwis need to know.

What’s Covid-19 doing in New Zealand right now?

Several months on from New Zealand’s last bump in Covid-19 cases, the Institute of Environmental Science and Research’s (ESR) wastewater and case surveillance suggests coronavirus activity is at its lowest in years.

The dominant variant since the middle of the year has been KP.3 - an Omicron offshoot that descended from the lineage JN.1, which fuelled our last summer wave.

More recently, ESR’s genomics and bioinformatics science leader Dr David Winter said, that’s branched off into another subvariant named KP.3.1.1, which has slowly been taking over.

Covid-19 activity is running at its lowest rates in more than a year. Image / ESR

“KP.3.1.1 continues to grow in Aotearoa, but that growth rate is relatively low and coinciding with overall low Covid-19 activity.”

What’s happening overseas?

Over the last few days, a new Omicron variant has been grabbing headlines in Europe and the US.

That’s “XEC” – a “recombinant” variant that has parts of its genetic material inherited from two different variants, each which descend from JN.1.

First detected in Germany in early August, it’s since been confirmed in more than 600 cases in more than two dozen countries across Europe, North America and Asia.

As at mid-September, it’s mainly been reported in the US, Germany, UK, Canada and Denmark – but that partly reflects the fact those countries routinely screen coronavirus variants.

The XEC variant of #SARSCoV2 has the most growth advantage of any circulating; updated graph below by @benjmueller (H/T @siamosolocani, @Mike_Honey_ ).
But it's a mystery why. This thread zooms in on the change in nucleocapsid as the potential explanation. https://t.co/1t3Khg8VBv pic.twitter.com/KysHOmzFfU

— Eric Topol (@EricTopol) September 21, 2024

At this point, it’s yet to make its way here, but that’s likely inevitable.

“We have updated our analysis pipelines to ensure they can find XEC genomes but have not detected any as yet,” Winter said.

He expected ESR’s current surveillance network would pick up a fast-growing variant like XEC before it reached 1% of cases in the community.

What else do we know about the variant?

Winter said international experience suggested the variant would have a “moderate” advantage over KP.3.1.1, so might replace it when it arrives.

“We will monitor the growth of this variant closely when it arrives.”

Covid-19 modeller Professor Michael Plank said XEC didn’t appear to be growing as quickly as JN.1 did last year.

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“So, if XEC does cause a wave in New Zealand, it will probably be a relatively small and slow one,” Plank said.

“It’s quite possible that another faster-growing variant will come along between now and the end of the year, but at the moment there’s no sign of that.”

Will XEC make people sicker?

So far, there’s not enough data to indicate whether the new variant is likely to cause increased disease severity – or put more people in hospital.

But, given its similar genetic material, experts think it’s likely to cause illness no worse than has been observed with earlier Omicron variants, with flu-like symptoms like a high temperature, sore throat, cough and body aches.

It’s also likely – as a recently-published New Zealand study showed – having been previously vaccinated and infected will help protect people from severe illness.

“The good news is that the protection against severe disease provided by the vaccines and by prior infection has remained strong, despite the procession of variants we’ve seen over the last couple of years,” Plank said.

Experts expect prior vaccination and infection will help guard against severe infection with the new XEC variant, as it has against earlier Omicron lineages.

“Covid-19 related hospitalisation rates are currently at their lowest level in almost three years. And accounting for our growing and ageing population, the total all-cause mortality rate in New Zealand is lower now than it was before the pandemic.”

Is another wave likely over summer?

That’s been the case for the last two years – and it’s unfortunately probable for these coming holidays.

“It is likely we’ll see some kind of wave over the summer – recently both hemispheres have been getting one wave in winter and one in summer – and it may be that this pattern continues, at least for the next couple of years,” Plank said.

Winter said that pattern was interestingly different from other respiratory nasties like flu and RSV.

“This is likely due to the virus being still so much younger than the ‘typical’ ones we have carried with us for a very long time,” Winter said.

“As Sars-CoV-2 keeps on finding new ways to infect us and get past our immune system, the evolution of the virus itself remains an important driver of waves.

“It’s unclear at the moment whether the virus will settle into a more seasonal pattern, or if we will continue to deal with ‘out-of-season’ waves.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.

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