Americans marked a grim Christmas holiday as coronavirus infections exploded nationwide, political leaders warned them not to travel or gather in large groups and a highly contagious variant of the virus spread further in Europe.
State and local political leaders nationwide have urged Americans not to travel for the holidays, saying that Thanksgiving celebrations had further spread the virus.
Many Americans, weary after more than nine months of lockdowns, have defied those warnings.
More passengers flew on commercial flights on Wednesday than any other day of the pandemic, with 1,191,123 passengers passing through airport checkpoints, according to data from the US Transportation Security Administration.
That number represents a drop from 2019, when 1,937,235 flew on December 23; but airports also recorded around 1 million travellers on each of the five days between last Friday and Tuesday.
Dr Anthony Fauci, the government’s top infectious disease expert, said he is particularly worried about travel between Christmas and New Year. Dr Fauci, who turned 80 on Thursday, said he and his wife would be celebrating his birthday and the holidays with their children on Zoom.
"We have a big problem," Dr Fauci told The Washington Post. "Look at the numbers – the numbers are really quite dramatic."
The virus has taken more than 327,000 lives in the US, with over 3,000 deaths per day repeatedly recorded over the past two weeks.
“We’re in a very very difficult situation right now. People are just not paying attention to public health guidelines, and the evidence for that is in the number of people travelling for the Christmas holiday,” said Dr Lee Harrison, a professor of medicine and epidemiology at the University of Pittsburgh.
The states of Tennessee and California have emerged as the epicentres of the latest surge
"Our state is ground zero for a surge in Covid-19 and we need Tennesseeans to their part," state Governor Bill Lee, a Republican, said in a tweet on Wednesday. Mr Lee asked residents of the southern state to wear masks and avoid large gatherings over the holidays.
Tennessee has recorded 119 new cases per 100,000 people over the last seven days, according to data from the Centres for Disease Control (CDC). California, the nation's most populous state, stood second at 105 cases per 100,000 people. Rhode Island and Arizona have also seen recent spikes.
More than one million people have received the first of two vaccine doses since December 14, according to the CDC. But the vaccinations have so far had little effect on the latest surge in cases spiralling nationwide.
Achieving herd immunity against the virus could require vaccination of up to 90 per cent of Americans, Dr Fauci, told the New York Times in an interview.
"We really don't know what the real number is. I think the real range is somewhere between 70 to 90 per cent," he said.
Dr Fauci, who is advising both Republican President Donald Trump and President-elect Joe Biden, a Democrat, on the pandemic, acknowledged that he had revised his estimates upward from earlier in the year, when he said the nation would reach herd immunity by inoculating 60 per cent to 70 per cent of the population.
Mr Fauci was vaccinated earlier this week on live television.
Health care workers, elderly nursing home residents, elected officials and firefighters are among those receiving the vaccines first. Most Americans have been told it could be six months or more before they are eligible for the shots.
Political leaders have come under criticism from both sides of the ideological spectrum for putting themselves at the front of the line.
Even as vaccination programmes give Americans a reason to hope that control of the pandemic may be in sight, an even more transmissible variant has spread rapidly in the United Kingdom.
The United States, unlike many nations worldwide, has not banned travellers from Britain but the governors of New York and Washington state have ordered travellers from the UK to quarantine on arrival.
