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New Covid subvariants not 'game changers' - modeller

A Covid-19 modeller says new subvariant strains will not cause waves of new cases if it arrives in New Zealand, but will likely leave a long tail of case numbers.

Test for coronavirus Covid-19. Female doctor or nurse doing lab analysis of a nasal swab in a hospital laboratory. Medical technologist holding a COVID-19 smear kit, wearing protective gloves from
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There are currently a number of Omicron subvariants worldwide including BA.1, BA.2 and XE which is a combination of those two, as well as the less common BA.4 and BA.5.

Last month, the Ministry of Health said BA.1 and BA.2 subvariants are both circulating in New Zealand, but the BA.2 subvariant is more dominant.

Australia's first case of XE was recently reported in a returned traveller, while it was reported on Friday that subvariant BA.4 or BA.5 (which one is yet to be determined) had been detected in Melbourne's wastewater.

Covid-19 modeller David Welch said the subvariants are likely to keep case numbers up to about a thousand a day in New Zealand.

"It's not as bad as it was at the peak of the wave, but that's still quite a lot of people getting infected every day.

"The variant mix might change a little but there's nothing to suggest at the moment that we're going to get a really big new wave or even that these new variants being reported are really going to change the landscape."

Welch said the subvariants are not any more contagious than Omicron at this stage.

"Some of the variants that have been reported on recently like XE, also like BA.4 and BA.5, yes they are different, they might have slightly different behaviours, but they're not going to be ... the game changers that we've seen with Alpha, Delta or Omicron."

University of Canterbury epidemiologist Arindam Basu said a shift in Covid hotspots seen this weekend is expected.

Auckland is no longer the centre of the Omicron outbreak in Aotearoa.

Auckland reported 869 new cases yesterday, but the Canterbury District Health Board region reported more than twice that with 2255 cases.

The Southern DHB yesterday had the second highest case number yesterday with 1747, while Waikato had 1079.

All other regions had fewer than 1000 cases yesterday and the seven day rolling average of case numbers continued to decline, with yesterday's seven-day rolling average at 8283, compared to 10,843 for the previous Saturday.

Basu expects cases in the regions further south will grow, then also taper off, in the coming weeks - a trend which he said started weeks ago.