By Michael Daly of 
The latest data shows the new subvariants on the rise, as the number of new cases identified as BA.5 fall. Photo: AFP
The main Omicron subvariant in this country is becoming less dominant as new subvariants rise up, recent data suggests.
But warming temperatures in the lead-up to summer could help limit an expected rise in new Covid cases.
Case numbers remained relatively flat last week, but that could change in the months ahead and it may be, in part, driven by new variants.
The latest Covid report from the Ministry of Health says that BA.5, which drove the recent winter wave now accounted for about 75 percent of cases in the two weeks to 30 September. That was the variant's lowest share of cases in months.
The BA.4.6 variant's share increased sharply in the latest data to 15 percent, while the BA.2.75 variant was also gaining and was up to 10 percent.
The ministry's report also said the Omicron BQ.1.1 lineage has not been detected in New Zealand in the fortnight to 30 September.
"However, as BQ.1.1 is rising rapidly in Europe at present, we might have a situation where we expected multiple new variants to be circulating, all with different immune evasion and severity profiles."
It is worth noting, however that just how Covid cases are sequenced has changed. For example, pre-departure testing is no longer required meaning we have an incomplete picture of what is coming in.
In a statement to Stuff, ESR said the latest variants counts should be interpreted with some caution, if for instance, you were comparing to older reports.
"The latest report reflects changes in New Zealand's reporting and surveillance system alongside the current Covid-19 situation.
"Major factors contributing to this are the lower volume of PCR results available for sequencing (RAT tests can't be sequenced). In addition, there is a discontinuity as a result of no longer separating community and border samples. And both the local and global picture is shifting which changing variant frequencies."
What about the severity of the new variants then? Well, a Ministry of Health report, dated 27 September, suggests: "There is no strong evidence of large increases in transmissibility or disease severity associated with the most recent variants.
"Vaccination, including boosters, remains effective at decreasing the risk of hospitalisation and death from Omicron. It remains difficult to predict the impact of variants here in Aotearoa New Zealand based on overseas trends as our infection history and hybrid-immunity differ from other countries."
Michael Plank said it looks like some new Covid variants are going to cause a wave in the Northern Hemisphere. Photo: Supplied.
Professor Michael Plank, from the University of Canterbury, said it appeared there was an increase in the share of some variants, but the picture was complicated.
As mentioned above, that was partly because the end of testing at the border had made it harder to distinguish between cases in the community and those at the border.
"That said, it does look like there is an increase in some of these other variants. That is consistent with what is being seen overseas. It's a bit difficult to quantify the speed of it," Plank said.
Internationally, a "whole host" of different lineages were showing up. They were all somewhat related, and were picking up similar sets of mutations.
It was hard to categorise them as just BA.4.6, as there were several versions of Omicron.
Covid cases and hospitalisations were rising in many countries, Plank said.
"It looks like some of these new variants are probably going to cause a wave in the Northern Hemisphere.
"We would expect a similar thing to happen here at some point, a few weeks later."
Countering that, warming temperatures as summer approached could be an advantage for this country.
"It maybe that our wave isn't as big because the Northern Hemisphere is going into a colder time of year and people are indoors more.
"Whereas, here we're moving towards summer, which makes it a bit harder for the virus to spread. It might reduce the size of the wave."
Covid cases and hospitalisations were rising in many countries. It wasn't clear that was entirely because of new variants, although they were probably playing a role, Plank said.
Other factors could be the move to colder weather in the Northern Hemisphere, and that people's immunity was waning over time.
This article was originally published on Stuff.
