NATURE – Little more than two months after it was first spotted in South Africa, the Omicron variant of the coronavirus SARS-CoV-2 has spread around the world faster than any previous versions.
Scientists have tracked it in more than 120 countries, but remain puzzled by a key question: where did Omicron come from?
There’s no transparent path of transmission linking Omicron to its predecessors. Instead, the variant has an unusual array of mutations, which it evolved entirely outside the view of researchers.
Omicron is so different from earlier variants, such as Alpha and Delta, that evolutionary virologists estimate its closest-known genetic ancestor probably dates back to more than a year ago, some time after mid-2020.
“It just came out of nowhere,” says Darren Martin, a computational biologist at the University of Cape Town, South Africa.
“Working out under what conditions this highly transmissible variant arose might help scientists to understand the risk of new variants emerging … “
The question of Omicron’s origins is of more than academic importance.
Working out under what conditions this highly transmissible variant arose might help scientists to understand the risk of new variants emerging, and suggest steps to minimize it, says Angela Rasmussen, a virologist at the University of Saskatchewan Vaccine and Infectious Disease Organization in Saskatoon, Canada.
“It’s very difficult to try to mitigate a risk that you can’t even remotely wrap your head around,” she says.
The World Health Organization’s recently formed Scientific Advisory Group for the Origins of Novel Pathogens (SAGO) met in January to discuss Omicron’s origins.
The group is expected to release a report in early February, according to Marietjie Venter, a medical virologist at the University of Pretoria in South Africa, who chairs SAGO.
Ahead of that report, scientists are investigating three theories. Although researchers have sequenced millions of SARS-CoV-2 genomes, they might simply have missed a series of mutations that eventually led to Omicron.
Alternatively, the variant might have evolved mutations in one person, as part of a long-term infection … Read more.