New Omicron sub-variants are causing Covid-19 cases to rocket in South Africa again.
Infections caused by BA. 4 and BA. 5 have surged in recent weeks, with the country officially entering its fifth wave of the pandemic earlier this week.
So what is different about the Omicron cousins, and should the world be worried?
The National explains.
How long have BA. 4 and 5 been around?
Experts in South Africa think BA. 4 and 5 emerged in mid-December and early January. In February they made up a tiny percentage of Omicron samples in South Africa, at just 0.34 per cent and 0.08 per cent respectively. At the time, BA. 2 dominated. By March, they had reached 14 per cent, and in April BA. 4 and 5 accounted for almost half, at 44 per cent.
Cases, and positivity rates, began climbing again in April as they took hold, following the steep fall after the end of the country’s large BA. 1 wave.
And they have been growing quickly.
On Thursday, the country recorded more than 6,300 new cases with a 21 per cent positivity rate.
That compared to around 4,400 cases with a 15.8 per cent positivity rate a week previously.
The latest numbers are the highest in almost three months and significantly more than two weeks ago.
Why are they causing infections to rise again in South Africa?
Professor Tulio de Oliveira, one of several scientists at South Africa's University of KwaZulu-Natal who first identified the Omicron variant, said BA. 4 and 5 share a similar spike to BA. 2, which is now dominant globally. But they have four additional mutations.
Of those, F486V shows the biggest potential for immune escape, experts said.
“F486V will further erode neutralisation of Omicron by current vaccines,” tweeted Jesse Bloom, a virologist Jesse Bloom at the Fred Hutchinson Cancer Research Centre in Seattle.
“In other words, Omicron BA. 1 and BA. 2 had already escaped a lot of neutralising antibodies elicited by current vaccines/early infections.
“F486V in BA. 4 and BA. 5 will escape a chunk of the remaining antibodies that still neutralise Omicron variants.”
He said that applies only to people who have antibodies from vaccines and pre-Omicron infections.
People who have been infected by BA. 1 and BA. 2 will probably react better to BA. 4 and 5, he said.
Have they been found anywhere else?
Yes. The variants are also present in more than 20 countries, including Botswana, Belgium, Germany, Denmark and the UK. These countries have good surveillance and sequencing systems, like South Africa. These are capable of detecting new variants early, so it is likely these variants are in many other countries too.
Will BA. 4 and 5 cause another wave of hospital admissions?
Ridhwaan Suliman, a researcher at the Council for Scientific and Industrial Research, a government research institute, tweeted that hospital admissions in South Africa have risen by more than 10 per cent recently. But he cautioned that was from a low base.
He told radio 702 in South Africa it was unlikely that the fifth wave, fuelled by BA. 4 and 5, will be coupled with high hospital admissions or deaths.
Hospital admissions and deaths fell during the fourth wave after the emergence of Omicron, he said.
“There's no indication to expect anything different at this stage,” Dr Suliman told the radio station.
Fellow South African scientist Professor Oliveira does not expect the fifth wave to cause a surge in hospitalisations and deaths in the country, either.
“Our main scenario for Omicron BA. 4 and BA. 5 is that it increases infections but that does not translate into large hospitalisations and deaths,” he tweeted.
