What do we know about the new Covid variant Omicron?

South African scientists have discovered a new Covid-19 variant, Omicron, with multiple mutations that is thought to be highly contagious.

The World Health Organization has designated it a variant of concern and many countries are racing to try and contain it, banning flights from southern Africa.

Scientists are working round-the-clock to dissect the variant and try understand its behaviour.

Here is a brief explainer of what is known so far about Omicron -- days after it emerged -- as shared by South African scientists.

- Origins -

It is currently unclear where the variant originated from, but South African scientists were the first to announce the discovery on November 25.

By that time cases had been detected in Hong Kong and Botswana. A day later, Israel and Belgium also uncovered the variant.

- Mutation -

Scientists discovered the new variant with a "very unusual constellation of mutations" on November 23.

Some of the mutations are already known, and affect transmissibility and immune evasion, but many others are new.

It has the "most mutations we have seen to date", said Professor Mosa Moshabela, Deputy Vice Chancellor of Research and Innovation at the University of KwaZulu-Natal.

He said "some of these mutations we have seen before like in Delta and Beta," but others they have not, and "we don't know what the combination of those mutations will translate into."

Leading virologist Tulio de Oliveira said there were around 50 mutations overall, including 30 on the spike protein, the focus of most vaccines as it is what enables the virus to enter cells.

- Transmissibility -

The pace at which the new daily Covid cases are increasing in South Africa has left scientists suspecting it may be driven by the transmissibility of the new variant.

Although not all are Omicron cases, the daily Covid positivity rate rose this week from 3.6 percent on Wednesday, 6.5 percent on Thursday, 9.1 percent on Friday and 9.2 percent on Saturday, according to official data.

"Some of the mutations that are expressed have previously been shown to enable the virus to spread easily and quickly, and because of that we suspect that the (new variant) is going to spread quickly," said Moshabela.

- Immunity, severity -

Some of the genetic mutations shown by the virus include those known to enable the virus to evade immunity.

It is unclear though what the impact will be on vaccines.

As for the severity of the variant, scientists say it has only come to light this week, giving little time for thorough analysis.