Clinical immunologist Dr Anthony Jordan gives advice on how to stay Covid safe this summer, while also enjoying the holidays after a 'rough three years'. Video / NZ Herald
The “variant soup” behind our Christmastime Covid-19 wave has only grown more complex, with tricky hybrid strains like the newly arrived Kraken making up a fast-growing chunk of sequenced cases.
While most coronavirus infections last year were caused by a handful of Omicron types – namely BA.2 and BA.5 - ESR’s latest surveillance update showed a diverse mix of lineages was now driving spread as the country moved out of its latest surge.
BA.5, largely responsible for last year’s winter wave, accounted for only about 9 per cent of cases sequenced over the month to January 13, with CH.1.1 making up roughly a third.
That subtype – a descendant of BA.2, which likely caused most of the country’s first Omicron infections – sported the same genetic mutations as the more recently introduced BQ.1.1, which already accounted for 15 per cent of cases.
Nicknamed Cerberus, BQ.1.1 and fellow BA.5 off-shoot BQ.1 (Typhoon) fuelled a tide of infections in the US and France last year, owing to their ability to better escape immunity from first and booster vaccines.
Also in the mix were BA.2.75, or Centaurus - a second-generation subvariant of BA.2 making up 17 per cent of cases – and a handful of “recombinant” strains created by two viruses swapping genetic material and typically designated with an X.
These include XBF (19 per cent of cases) XBC (4 per cent) and XBB (2 per cent) - and at presently low levels, the freshly-detected XBB 1.5, better known as Kraken.
The World Health Organisation (WHO) has labelled Kraken – now causing large numbers of infections across the US - “the most transmissible subvariant that has been detected yet”.
It’s also been detected in Australia, the UK and several European countries including Denmark, France, Germany and Spain.
According to the US Centres for Disease Control and Prevention (CDC), more than 40 per cent of the country’s infections have been caused by XBB.1.5.
This month, Otago University epidemiologist Professor Michael Baker warned it could also drive many more infections here - although there were some promising signs its global growth was slowing.
There are some signs now that XBB.1.5 is loosing steam as it spreads through the wider population.
The share of cases has increased more slowly in the US and UK, recently.
Otago University evolutionary virologist Dr Jemma Geoghegan said it wasn’t unexpected to see these mutant strains making up such a big part of the picture, given so many variants were now circulating together.
Scientists have watched many of these strains develop independently – while acquiring similar traits in response to the same selective pressures – making for one of the world’s most fascinating cases of “convergent” evolution.
Nevertheless, Geoghegan said the rate at which strains were emerging continued to surprise.
“We’ve got a few examples of this happening in nature, but not too many in virus evolution.”
The question facing scientists now was whether Omicron – today a family of hundreds of identified lineages – stayed in the pandemic’s driver’s seat.
Otago University virologist Dr Jemma Geoghegan.
“It’ll be interesting to see what happens next, and if it continues on its path, we’re going to see a lot more convergent evolution and recombination,” Geoghegan said.
The Government is soon expected to roll out new “bivalent” boosters that target the BA.5 subvariant and have been shown to perform better against new Omicron strains.
Reported cases hit three-month low
Meanwhile, reported weekly Covid-19 cases have dropped to the lowest levels in three months, as New Zealand climbs down from the Christmas time bump.
The Ministry of Health reported 13,880 new community cases in the past week, along with 242 people in hospital with the virus as at midnight Sunday.
Another 79 deaths have also been linked to the virus - including one person younger than 10 years old, and two people in their 20s.
Of the others, two in their 40s, seven in their 50s, 12 in their 60s, 10 in their 70s, 27 were in their 80s and 18 were aged over 90. Of these people, 50 were women and 29 were men.
The ministry reported two of the dead were from Northland, 24 from Auckland region, six from Waikato, five from Bay of Plenty, two from Lakes, one was from Tairawhiti, two were from Hawke’s Bay, one from Taranaki, six from MidCentral, three from Wellington region, three from Nelson Marlborough, 12 from Canterbury, two from South Canterbury and 10 from Southern.
