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NSW has recorded its first case of a new, highly-contagious Omicron subvariant, heightening concerns the Ba.4 strain will lead to a rise in Covid reinfections.
The state’s health department confirmed on Thursday the BA.4 infection was found in a returned traveller from South Africa earlier this month.
The new strain is behind a recent rapid rise in Covid cases in South Africa, and appears to be quickly achieving dominance over the original Omicron and other versions of the virus.
Experts say BA.4 seems to be more transmissible than both BA.1 and BA.2.
Scientists are still studying the new mutant, but the World Health Organization said in a recent report that it doesn’t appear to be more severe than other versions.
WHO confirmed it was monitoring the growth advantage of BA.4 and BA.5, which could be taking advantage of waning immunity from prior infections.
James Wood, a mathematician at UNSW’s School of Public Health and Community Medicine, told The Sydney Morning Herald this week Australia will see an increase in transmission caused by new sub-variants “within the next couple of months”.
“BA.4 and BA.5 in South Africa are clearly causing cases to go up, and we can expect these are already here in low numbers,” he said.
The USA is overwhelmed by #Omicron #BA2variant right now. But #SouthAfrica has been about 6 weeks ahead of us on #COVID19 trends, and it's getting hit by BA.4&5 (orange and brown in chart). pic.twitter.com/csVzfZCvsK
— Laurie Garrett (@Laurie_Garrett) April 28, 2022
James McCaw, an epidemiologist and mathematical biologist with the University of Melbourne, told the publication “reinfections will become the norm”.
“But what we hope is repeat infections will be milder each time as natural immunity combined with vaccination generates strong protection,” he said, adding that Covid “will be around forever because of reinfections”.
South Africa's BA.4 spike a prediction of what's to come
Experts have pointed to South Africa’s spike in Covid cases as a model for what the rest of the world can expect in the coming weeks.
The country’s infections began to rise rapidly last week — with just over 6000 cases a day being recorded, up from a few hundred just a few weeks ago.
So far, there has been only a slight rise in hospitalisations and no increase in deaths, Salim Abdool Karim, who is a public health expert at the University of KwaZulu-Natal, says.
The new mutant appears to be quickly achieving dominance over the original omicron and other versions of the virus, but Abdool Karim said “it’s too early to tell whether BA.4 is going to cause a fully-fledged wave”.
Still, the new version is notable because the Omicron variant first emerged in November in South Africa and Botswana before sweeping around the world.
“The BA.4 & BA.5 Omicron subvariant-driven increase of new confirmed Covid cases in South Africa gives a good idea of what the endemic equilibrium will look like: a significant wave every 6 months with significant mortality and morbidity,” Tom Wenseleers, a professor of evolutionary biology at KU Leuven, tweeted this week.
Pulitzer Prize winning journalist Laurie Garrett said the country’s new wave is a good prediction of what is to come.
“The USA is overwhelmed by Omicron and BA.2 variant right now. But South Africa has been about six weeks ahead of us on Covid-19 trends, and it’s getting hit by BA.4 and 5,” she said.
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