Omicron: what we know and don't know

South African Health Minister Joe Phaahla said the variant was linked to an "exponential rise" of cases in the country in the past few days.

From just over 200 new confirmed cases a day in recent weeks, South Africa saw the number of new daily cases rocket to more than 3200 on Saturday, with most in Gauteng.

Faced with the sudden rise in cases, scientists studied virus samples and discovered the new variant.

Now, as many as 90 per cent of the new cases in Gauteng are caused by it, according to the KwaZulu-Natal Research Innovation and Sequencing Platform.

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WHY ARE SCIENTISTS WORRIED?

The World Health Organisation said "preliminary evidence suggests an increased risk of reinfection with this variant", meaning people who contracted COVID-19 and recovered could catch it again.

The variant appears to have a high number of mutations - about 30 - in its spike protein, which could affect how easily it spreads to people.

Sharon Peacock, who has led coronavirus genetic sequencing in Britain at the University of Cambridge, said the data suggested Omicron had mutations "consistent with enhanced transmissibility", but said "the significance of many of the mutations is still not known".

Lawrence Young, a virologist at the University of Warwick, described Omicron as "the most heavily mutated version of the virus we have seen", including potentially worrying changes never before seen in the same virus.

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WHAT'S KNOWN AND NOT KNOWN ABOUT THE VARIANT?

Scientists know Omicron is genetically distinct from previous variants including Beta and Delta, but do not know if these changes make it any more transmissible or dangerous. So far, there is no indication the variant causes more severe disease.

It will likely take weeks to sort out if Omicron is more infectious and if vaccines are still effective against it.

Peter Openshaw, a professor of experimental medicine at Imperial College London, said it was "extremely unlikely" that current vaccines would not work, noting they were effective against numerous other variants.

Even though some of the genetic changes in Omicron appear worrying, it's still unclear if they will pose a public health threat. Some previous variants, such as Beta, initially alarmed scientists but did not end up spreading very far.

South Africa's Dr Angelique Coetzee, who was one of the first to suspect a different coronavirus variant, said symptoms of Omicron were so far mild and could be treated at home.

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HOW DID THIS NEW VARIANT ARISE?

The coronavirus mutates as it spreads and many new variants often just die out. Scientists monitor coronavirus sequences for mutations that could make the disease more transmissible or deadly, but they cannot determine that simply by looking at the virus.

Peacock said Omicron "may have evolved in someone who was infected but could then not clear the virus", giving it the chance to evolve in a scenario similar to how the Alpha variant - which was first identified in England - likely emerged, by mutating in an immunocompromised person.

AP with PA

Australian Associated Press