The Delta variant, known by the scientific name B.1.617.2, has spread from where it was first discovered in India to over 60 countries, according to the World Health Organization, Xinhua reported.

More than 6 percent of the sequenced Covid-19 infections in the US trace to the highly transmissible Delta variant, Fauci said on Tuesday.

The variant has become the dominant strain in the UK, accounting for an estimated 60 per cent of new cases, replacing the B.1.1.7 strain, according to Fauci.

He called on more Americans to get vaccinated to keep the new variant from proliferating across the country.