Omicron, first found in South Africa, has been identified in at least 12 other countries.
The new Omicron variant of Covid poses a "very high" global risk and could have "severe consequences" where there are surges, the World Health Organisation (WHO) said on Monday, adding that it is not yet known how contagious and dangerous it is.
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The Omicron variant is likely to spread internationally, the WHO said, urging countries to prepare by accelerating vaccinations and put mitigation plans in place to maintain essential health services.
"Omicron has an unprecedented number of spike mutations, some of which are concerning for their potential impact on the trajectory of the pandemic," WHO said in a statement.
"If another major surge of Covid-19 takes place driven by Omicron, consequences may be severe," said a technical note, adding though that "to date, no deaths linked to Omicron variant have been reported."
"The overall global risk related to the new variant of concern Omicron is assessed as very high," said the organisation. More research is needed to understand Omicron's potential to escape protection against immunity induced by vaccines and previous infections, said WHO.
WHO on Friday declared Omicron a "Variant of Concern", placing the new strain into the most troubling category of Covid variants, along with Delta, and its weaker rivals Alpha, Beta and Gamma.
Crucial data on Omicron is expected in coming weeks. WHO believes it can affect vaccinated people too. "COVID -19 cases and infections are expected in vaccinated persons, albeit in a small and predictable proportion," it said.
Omicron, first found in South Africa, has been identified in at least 12 other countries. Cases have emerged in Botswana, Italy, Hong Kong, Australia, Belgium, United Kingdom, Denmark, Germany, Canada, Israel and Czech Republic.
Several countries have already imposed travel bans and restrictions on flights to and from South Africa and neighbouring countries.
Japan and Israel have barred foreigners. Australia says it will review plans to re-open borders to skilled migrants and students from December.
India will make on-arrival testing mandatory for those arriving from countries where 'Omicron' has been found. Every international passenger coming to India has to fill a self-declaration form and show a negative RT-PCR test report. They can't enter India if any of these two conditions are not fulfilled.
