South African scientists are working “at lightning speed” to ascertain how quickly the concerning new coronavirus variant can spread and whether it is resistant to Covid-19 vaccines.

Results will still take at least two weeks, Tulio de Oliveira, a bio-informatics professor who runs gene-sequencing institutions and advises the government on the pandemic, said by phone on Friday. Institutions are breeding the virus and then experimenting on it, he said, not just in South Africa but around the world.

“I am very, very worried,” he said of the virus variant, which has more mutations than earlier incarnations and has already been detected in Botswana and Hong Kong.

While the variant has still only been identified in a relatively small number of cases, the fears expressed by scientists have reverberated around the world. The UK has banned flights from South Africa and five neighboring countries ahead of placing them on its so-called red list, which requires hotel quarantine. Stocks, Treasury yields and oil all sank while the rand weakened to a one-year low.