A very good piece on the new variant. "Scientists, meanwhile, are hard at work trying to figure out whether B.1.1.7 is really more adept at human-to-human transmission—not everyone is convinced yet—and if so, why" https://www.sciencemag.org/news/2020/12/mutant-coronavirus-united-kingdom-sets-alarms-its-importance-remains-unclear

"scientists have never seen the virus acquire more than a dozen mutations seemingly at once. They think it happened during a long infection of a single patient that allowed SARS-CoV-2 to go through an extended period of fast evolution" https://www.sciencemag.org/news/2020/12/mutant-coronavirus-united-kingdom-sets-alarms-its-importance-remains-unclear

"Scientists previously worried that a variant that spread rapidly from Spain to the rest of Europe...might be more transmissible, but today they think it is not; it just happened to be carried all over Europe by travelers who spent their holidays in Spain" https://www.sciencemag.org/news/2020/12/mutant-coronavirus-united-kingdom-sets-alarms-its-importance-remains-unclear

"the strain from Spain, offers a cautionary lesson, says virologist Emma Hodcroft of . . Basel. U.K. scientists initially thought it had a 50% higher mortality rate, but that turned out to be “purely messy, biased data in the early days,” she says." https://www.sciencemag.org/news/2020/12/mutant-coronavirus-united-kingdom-sets-alarms-its-importance-remains-unclear

"Other countries may well have the variant as well, says epidemiologist William Hanage ...; the United Kingdom may just have picked it up first because that country has the most sophisticated SARS-CoV-2 genomic monitoring in the world."
https://www.sciencemag.org/news/2020/12/mutant-coronavirus-united-kingdom-sets-alarms-its-importance-remains-unclear