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Helix, a San Diego-based genomics firm, has been watching the BA.2 variant since it first popped up in the US in early January. Although it was initially slow to take hold, Helix now estimates that 50 per cent to 70 per cent of all COVID-19 cases in the US are BA.2, Bloomberg reported.
White House Chief Medical Advisor Dr Anthony Fauci said BA.2 is 60 per cent more transmissible than Omicron, but it does not appear to be more severe. "It does have an increased transmission capability," Dr Fauci told ABC News.
Timely vaccination and booster shots remain the best means to prevent serious illness from the virus, Dr Fauci said, adding the variant has already caused a surge in COVID-19 cases in China and parts of Europe.
Some experts say BA.2 may be only 30 per cent more contagious than its predecessor BA.1, as against Dr Fauci's estimate of 60 per cent. This subvariant is sometimes called "stealth Omicron" because it is more difficult to detect.
According to the World Health Organisation (WHO), BA.2 differs from BA.1 in its genetic sequence, including some amino acid differences in the spike protein and other proteins. Studies have shown that BA.2 has a growth advantage over BA.1. Studies are ongoing to understand the reasons for this growth advantage, but initial data suggest that BA.2 appears inherently more transmissible than BA.1.
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