The last Sunday of 2020 was ushered in with both promise and apprehension on the global pandemic front.

The European Union began immunizing residents with the Pfizer-BioNTech vaccine. "We are starting to turn the page on a difficult year," said the president of the European Commission, Ursula von der Leyen, in a video posted on Twitter. The E.U. she added has "secured enough doses for our whole population of 450 million people."

At the same time, some of the year's most severe lockdowns and travel restrictions are being implemented around the world, prompted by concerns that new variants of SARS-CoV-2, the virus that causes COVID-19, could lead to more rapid spread.

The U.K. variant, which is now the dominant strain in Britain, "may be more transmissible than previously circulating variants, with an estimated potential to increase the transmissibility of the virus by up to 70%," according to a statement from the U.S. Centers for Disease Control and Prevention. There are similar concerns about a new strain from South Africa that may be circulating in other countries as well.

On the domestic front, travelers arriving in the U.S. from the U.K. are now required to show proof of a negative COVID-19 test under new rules issued by CDC on Christmas day.

More than 40 other nations have gone even farther, blocking travelers from Britain entirely. Despite such measures, the new strain has already been detected in mainland Europe, Israel, Canada and Japan, among other places.

In response Japan is banning nearly all foreigners (the declaration lists nationals from 152 countries as personae non gratae at least until February) and is imposing new restrictions on Japanese citizens returning from any country that's reported cases of the U.K. variant. The new Japanese rules also apply to places where the South African strain is circulating.

A surge in cases and concerns over the more highly transmissible forms of the virus prompted Israel to go into its third lockdown on Sunday. For at least the next two weeks, Israelis are prohibited from visiting someone else's home or traveling more than 1,000 meters from their own home – a little more than half a mile. All non-essential businesses are shut. Restaurants can only offer take out.

Gatherings such as weddings and funerals in Israel will be limited to 10 people indoors and 20 outside. This is generous compared to Hong Kong, which has put in place a "prohibition of group gatherings of more than two persons." On Sundays in Hong Kong foreign domestic workers traditionally have the day off. Groups of women from the Philippines and Indonesia gather in small groups in parks and on sidewalks all across the city. They often share soft drinks and snacks. Municipal officials are now calling for them to stay home at their employer's apartments.

Hong Kong is also increasing quarantine requirements for incoming travelers. While some other places are shortening COVID quarantines from 14 days down to 10 or 7, Hong Kong is now requiring a mandatory 21 days. The quarantine is at the travelers own expense in a government-sanctioned hotel.

Thailand, which had kept its daily tally of reported COVID-19 cases in the single digits for much of the pandemic, is grappling with its worst surge to date. Since mid-December, the country has seen a sharp rise in cases linked originally to a seafood market, including 121 new infections on Sunday. The spike in cases in Thailand has not been tied to the U.K. variant. But it illustrates that even countries that appear to have the disease under control can't let their guard down.

South Korea, which successfully contained two earlier waves of COVID-19, is facing record numbers of new cases and a spike in fatalities.

The United States, which already has the largest number of cases globally and regular reports of more than 200,000 new infections a day, is also bracing for grim numbers ahead. Over the weekend top health officials warned that travel and family gatherings during this holiday season are likely to lead to a further spike in cases.

"As we get into the next few weeks, it might actually get worse," Anthony Fauci, the nation's top infectious disease expert told CNN on Sunday.

Even though the U.K. variant hasn't yet been detected in the U.S., many top immunologists believe it may already be circulating here.

"I think it's prudent and a good idea to do some form of testing, and not let somebody on the plane from the U.K. unless they have a documented negative COVID-19 test," Fauci said. Given the high levels of transmission already occurring in the U.S., a more transmissible form of the virus could mean more even more dire numbers just as massive vaccine campaigns are starting.

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