The BA.5 variant of Omicron starts “snowballing” and Covid-19 case numbers may start to rise as a result.
The Institute of Environmental Science and Research (ESR), with the support of some scientists, now expects the BA.5 variant to overtake BA.2 as the dominant Covid strain in Aotearoa by the end of July.
Models suggest BA.5 may be responsible for more than half of daily infections in as little as two weeks.
Dr David Welch, a senior lecturer and Covid-19 modeler at the University of Auckland, said he believed a slight bump in national case numbers over the past few days could even be the start of a BA.5 wave.
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Welch said that over the past month, the incidence of BA.5 has effectively doubled every week in consecutive cases and last week’s sequencing found the BA.5 variant in 10% to 20% of cases.
If that trend held, BA.5 could reach 50% as early as mid-July.
BA.2 would then effectively disappear in the next few months as BA.5 and others outcompeted it, Welch said.
SUNGMI KIM / Stuff
A slight increase in case numbers over the past week may be the first signs of a BA.5 wave starting, says Dr David Welch.
It is important to note that BA.5 and BA.4 are not considered more serious versions of Omicron.
But they are spreading because they have proven around the world that they are more effective at evading immunity against vaccination and previous infections.
The two cause minor Covid waves in several countries around the world, increasing the number of cases and increasing hospitalizations with small amounts in countries such as Britain, Portugal, France and Israel.
South Africa, the first country to record BA.4 and BA.5, had a small wave of hospitalizations in May attributed to the variants – reaching 35% of its initial Omicron peak.
Hospitalizations have since failed sharply again.
It remains to be seen whether Aotearoa will experience the same bump in cases or hospitalizations when BA.5 becomes dominant.
The evolutionary virologist from the University of Otago, Jemma Geoghegan, notes on BA.4 and BA.5 has a similar genomic profile as BA.2, while BA.2 has noticeable differences with BA.1.
Because BA.2 has quickly become the dominant Omicron variant in New Zealand (making up 86% of the overall sequence of Omicron cases), our immunity profile differs from most countries that experienced BA.1 waves first.
Geohegan says this exposure to BA.2 could keep us in the right place to ward off the worst effects of a BA.5 wave.
Supply
Dr Jemma Geoghegan, University of Otago virologist, says our wave of BA.2 can help prevent BA.5’s spread.
Welch agrees, but is confident that there will be some more consequences if BA.5 shifts BA.2, believing that we may even see it.
‘We have been in a New Zealand period of plateau or declining fall numbers, but only for the last few days have we seen an increase.
“It may be a bit of a flash, but it certainly fits in with the observation that BA.5 is increasing, and quite fast in some places.
“We may be at the beginning of a new wave now.”
A Health Ministry spokesman said in a statement accompanying his daily numbers on Tuesday that an increase in case numbers was “not uncommon after a long weekend”, and more time was needed to determine if it was part of ” a trend is.
ESR’s top genomics scientist Michael Bunce said Omicron’s new “flavors” will surpass BA.2, and are likely to lead to either a wave or a bump of cases before the end of winter.
BA.5 shows all the signs that it is a snowball and that it will become the dominant tribe.
“It has an advantage, and it does not require much of an advantage. As soon as the snowball starts rolling, you end up with a displacement wave. ”
Matt Rourke / AP
Vaccination will be important to help increase the immunity profile of Kiwis this winter.
Bunce said wastewater testing from 20 sites across New Zealand in mid-June still had BA.2 at 95% incidence, while BA.4, BA.5 and BA.2.12.1 were around 5%, although changing rapidly has.
“One of the things that made it more challenging for us to predict this time is that we have always had the luxury of being able to look at what other countries are doing.
“But these other countries were eager to massively scale down their oversight networks.
“Especially the US and especially the UK, we are now more in the dark about the impact of these variants on portability than we were in the past.”
Welch said follow-up data in New Zealand remains limited in its scope – ESR has arranged between 400 and 500 cases per week in succession, although it aims to further increase it.
Despite the low numbers and the struggle for region-specific data, Welch said he feels confident that the patterns the sequence data tells us about BA.5’s rise would be true.
“I think it is very important that people continue to do what they can to prevent them from being infected by Covid.
“We must be aware that there are already many diseases, as well as with the flu season that will increase over the next few months.
“I would definitely encourage anyone who is eligible who did not get a third or fourth shot from next week to go out and get one.”