The United States has surpassed 12 million Covid-19 cases, according to the Johns Hopkins University real-time tracker.

The world's largest economy currently has 12,019,960 cases and 255,414 deaths, both by far the worst global tolls. The new toll comes just six days after the US crossed the 11-million case threshold.

Cases have been surging in the US at an alarming rate, forcing many cities to re-impose punishing lockdown measures.

Health authorities have urged people to stay home for next week's Thanksgiving holiday, when Americans usually travel from coast to coast to be with their families.