On Friday, the World Health Organization (WHO) renamed the new variant and has designated it a "variant of concern".
Earlier in the day, Belgian Health Minister Frank Vandenbroucke confirmed his country has detected one case of the variant and said it was in a person who had "come from abroad".
The infected person was reported to be a young adult woman who had developed symptoms 11 days after returning from a trip to Egypt via Turkey.
Marc Van Ranst, who works with the Rega Institute in Belgium, tweeted that a sample was confirmed as the variant in a traveller who returned from Egypt on November 11. The patient first showed symptoms on November 22.
Belgium, along with its neighbour the Netherlands, took new measures on Friday in an attempt to keep curb a spike in infections in the run up to Christmas.
Several countries, including the UK, have banned flights from the southern African region. The EU has now imposed a ban on flights from southern Africa. Several EU nations had already enforced flight bans of their own before the bloc's decision.
EU Commission President Ursula von der Leyen said flights “should be suspended until we have a clear understanding about the danger posed by this new variant, and travellers returning from this region should respect strict quarantine rules.”
Howeber, the chair of the South African Medical Association has described the travel restrictions imposed on the country as “hasty” and the reaction from other countries as “a storm in a teacup”.
Dr Angelique Coetzee said it was too early to tell what impact the B.1.1.529, or Omicron, variant would have.
She told BBC News: “We think it is a premature decision that has been taken, I think it is a hasty decision.
“I would understand if it was two weeks later and we know much more about this viral infection that is going around, or this mutation, but for now, it is like a storm in a teacup."
This comes after Israel reported it detected Omicron in a traveller who had returned from Malawi, and was investigating two other suspected cases. All three had been vaccinated.
In response, Israel's Prime Minister Naftali Bennett said the country was “on the threshold of an emergency situation” and barred travel to and from most African countries.
As cases rise in continental Europe, new measures in Belgium see nightclubs close once again, while bars and restaurants have to close at 11pm for the next three weeks.
Prof Mark Woolhouse, Professor of Infectious Disease Epidemiology, University of Edinburgh said travel restrictions could only delay the spread of a highly transmissible variant rather than prevent it.
"If B.1.1.529 is more transmissible than Delta then it will arrive in the UK sooner or later; Delta spread all over the world earlier this year.
"The role of travel restrictions is to buy us some time and their value depends on what we do with that time.
"The priority must be to establish whether B.1.1.529 really does pose a significant threat to public health. If it does then we have a suite of tools available to lessen its impact."
The Omicron variant which was first identified in southern Africa, is thought to be more more transmissible that current variants and may be more resilient to vaccines.
Transport Secretary Grant Shapps told ITV News on Friday that "in the end these things spread everywhere" and his move to place six countries on the red list is only about delaying the mutation's arrival into the UK. The UK has reported no cases of Omicron so far.
South Africa, Botswana, Lesotho, Eswatini, Zimbabwe and Namibia were added to England's travel red list on Friday. This means passengers arriving in the UK from these countries from 4am on Sunday will be required to book and pay for a Government-approved hotel quarantine for 10 days. Downing Street urged anyone who has arrived from these countries recently to get tested.
South African scientists raised concerns over the variant, which they fear is behind a spike in cases in some regions, including Gauteng province, which includes the cities of Pretoria and Johannesburg.
Which countries have reported cases of the new variant?
South Africa - 100
Israel - 3
Hong Kong - 1
Belgium - 1
Botswana - 4
Countries now on England's travel red list: