South Africa logged its millionth case of Covid-19 and South Korea on Monday became the latest country to detect the new coronavirus variant, as the pandemic showed no signs of letting up.

Global infections have raced past 80 million with nearly 1.8 million deaths, even as vaccination drives gather pace in North America and Europe, with a top US expert warning that the pandemic might get even worse in the coming weeks.

The explosion of cases worldwide in recent weeks has prompted the return of many unpopular restrictions, including some lockdowns, and concerns have grown after the detection of a new virus variant experts believe could be more transmissible.

South Africa became the first African nation to log one million cases, official data showed Sunday, as authorities considered reimposing restrictions to battle a second wave of infections driven by the new variant.

South Korea became the latest nation Monday to detect the variant, in three individuals of a London-based family who arrived in the country last week.

The new variant was first detected in Britain, and made its way to a number of other nations including Japan and Canada, prompting dozens of governments -- including European nations -- to impose travel restrictions on the UK.

Most European countries began their vaccination campaigns over the weekend, boosting hopes of an end to the pandemic, especially in some of the hardest-hit parts of the continent.

"Today is a big moment when you think back to all that we have been through... especially during the first wave of the pandemic," said Isabella Palazzini, an Italian nurse in Cremona.

"They were very difficult times, both for the patients and for us, the care givers," said Palazzini, three of whose colleagues died of Covid-19.

Worst yet to come

Known coronavirus infections surged past 19 million in the United States on Sunday, the worst-hit country in the world, adding a million cases in less than a week.

US cases have been surging at an alarming rate in recent months. The world's largest economy has added at least one million new cases per week since early November, according to Johns Hopkins University data.

But there was some relief for Americans Sunday when President Donald Trump finally signed a $900 billion stimulus bill, a long-awaited boost for millions of people whose livelihoods have been battered by the pandemic.

While the United States has also begun vaccinations, experts have said that because of the expected surge in cases over the Christmas holidays, the situation could get much worse.

Top US government scientist Anthony Fauci warned Sunday that the worst of the pandemic may be yet to come, driving the United States to a "critical point" as holiday travel spreads the coronavirus.

About two million Americans have been vaccinated so far, well below the 20 million the Trump administration has promised by year-end.

But Fauci played down the shortfall as a normal hiccup in a massively ambitious project, saying he was "pretty confident" that by April, all higher-priority people would have been able to get vaccinated, clearing the way for the general population.

'Food for thought'

Vaccination campaigns have also begun in China, Russia, Canada, Singapore and Saudi Arabia, and there was hope for one more successful vaccine on the horizon.

Poland on Monday began a three-week partial lockdown, and as Israel began a third spell of its most stringent restrictions over the weekend, Prime Minister Benjamin Netanyahu voiced optimism that a "world record" vaccination drive will restore a degree of normality within weeks.

But there are worries that vaccine hesitancy or outright refusal -- especially because of anti-vaccine misinformation campaigns.

Polls have shown many Europeans are unwilling to take the vaccine, which could impede efforts to beat the virus and reach widespread immunisation.

A young German pilot found a unique way to raise awareness, tracing a giant syringe in the sky to mark the start of his country's rollout of vaccines.

"I wanted to give people food for thought for the day the vaccine became available," Kramer, a student and amateur pilot, said Sunday.