South Africa's health ministry, in an urgent media briefing yesterday, announced the detection of a new SARS-CoV-2 variant, B.1.1.529, that has quickly outpaced the Delta (B1617.2) variant and has a host of mutations that might change how the virus behaves.The new findings triggered an unprecedented and fast response in science and government ranks yesterday, with experts raising deep concerns about the new variant's mutation profile and the World Health Organization (WHO) today convening its technical advisory group (TAG), with speculation swirling that it would designate B.1.1.529 as the fifth variant of concern and name it Nu.Also yesterday, countries—including Israel and the United Kingdom—began barring flights from South Africa and