Paul Hunter, professor of medicine at the Norwich School of Medicine at the University of East Anglia, told CNBC Wednesday that, given the earliest known omicron sample was taken on Nov.9 in South Africa, “clearly the infection must have been circulating a little before that unless the index case was the person in whom the variant evolved, but probably not much earlier.”

While Danny Altmann, professor of immunology at Imperial College London, said he’d “certainly agree it’s a possibility” that the omicron variant was spreading earlier than November, and that there was no certainty it originate in South Africa.

“The point that it came to attention through rising cases and excellent sequencing around Goateng [in South Africa] from the second week of November neither proves it arose near there or that this was the starting point.”