New Delhi, June 17 Several countries including India, the UK, US, and Australia are seeing an uptick in Covid cases majorly driven by Omicron sub-variants BA.4, BA.5, according to media reports.
The more transmissible sub-variants, that emerged in South Africa early this year, are added to the World Health Organisation's (WHO) monitoring list, while Europe has designated them as variants of concern.
BA.5 is enroute to become dominant in most European countries including the UK and Portugal. The US and Australia are also seeing rising numbers of infections caused by the two new sub-variants.
In India, sequenced data from Maharashtra, Telangana and Tamil Nadu has confirmed the presence of the sub-strains of Omicron.
Prof Azra Ghani, an epidemiologist at Imperial College London, said the rising number of infections were not surprising, and might increase further.
"This increase in infection prevalence is likely due to the growth of the BA.4 and BA.5 Omicron subvariants, which as we have seen elsewhere in Europe, appear to be able to escape immunity generated from previous Omicron subvariants," she was quoted as saying to the Guardian.
"It is therefore possible that we will continue to see some growth in infection prevalence in the coming weeks and consequently an increase in hospitalisations, although these sub-variants do not currently appear to result in any significantly changed severity profile. This does however serve as a reminder that the Covid-19 pandemic is not over," Ghani said.
BA.4 and BA.5 Omicron are not thought to be any more lethal than other types of Covid. But the two new variants are thought to spread more quickly than BA.2, which itself was more contagious than the original Omicron.
Several studies have also shown that BA.4 and BA.5 are more transmissible and also have the ability to avoid immunity induced by both previous Covid infection and vaccination.
"BA.4 and BA.5 evade existing immune responses from both infection and vaccination better than previous Omicron sub-variants, and that's why (they have) a transmission advantage," Associate Professor James Wood, a mathematician at University of New South Wales, was quoted as saying to the Sydney Morning Herald.
The high transmission level is partly also because immunity may be waning, and also because of the mutations the virus has undergone.
Many countries have also lifted their Covid restrictions, meaning people are mixing more, which gives the virus more chances to spread. BA.4 and BA.5 also appear to be able to infect people even if they've recently had other types of Omicron.
While it is not clear "how big the wave will be or how deadly" it will be, "consistent with the overall picture, we're starting to see an upswing after two months of decline,a driven by the sub-variants, John Roberts, an actuary tracking Covid, told the Telegraph.
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