Infectious disease experts are keeping a close eye on an even more contagious version of the Omicron variant spreading in the US, fuelling concerns that the country may not return to normal, said a media report.

The virus, known as BA.2, is a strain of the highly contagious Omicron variant that appears to spread 30 per cent more easily, Xinhua news agency quoted the report by National Public Radio (NPR).

BA.2 is found to have quickly overtaken the original Omicron strain in South Africa and other countries and has even caused a second surge of the variant in Denmark.

Researchers cautioned the same could happen in the US, raising fears that the spread "may be on track to rapidly accelerate in the near future", according to the report.

As of Wednesday morning, the US continues to be the worst-hit country with the world's highest number of cases and deaths at 78,642,385 and 938,938, according to the Johns Hopkins University.

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