The highly contagious UK Covid-19 variant is between 30 to 70 per cent more deadly than the original strain of the virus, British scientists are warning.

Infected people have a higher viral load, or more of the virus in their body, meaning more severe Covid-19 symptoms.

The British variant has now been discovered in 82 countries, with cases linked to the strain doubling in the US nearly every 10 days.

Scientists warn that the UK variant is expected to be the dominant strain in the US as early as March.