Analysis by Dr Nicholas Davies, from the London School of Hygiene and Tropical Medicine (LSHTM), suggests there were around 60 cases already in England by November 28, yet only 22 have been reported by the UK Health and Security Agency (UKHSA).
A science advisor to the government has also warned that Omicron cases in England are likely to already be triple the official number.
WHO experts reiterated calls for a rethink on travel bans against southern Africa, given that omicron had now been reported in nearly two dozen countries and its source remained unclear.
“South Africa and Botswana detected the variant. We don’t know where the origin of this could have been,” said specialist Ambrose Talisuna. “To punish people who are just detecting or reporting… is unfair.”
Omicron accounted for 74 per cent of the 249 virus genomes sequenced in South Africa in November, according to the National Institute for Communicable Diseases (NICD), which is collecting data as part of a wider national network for genomic surveillance.
News.band has reported that the new Covid-19 variant, Omicron, was present in the Netherlands earlier than previously thought.
It was identified in two test samples taken in the country between 19 and 23 November, which is before the variant was first reported by South Africa.
It is not clear whether those who took the tests had visited southern Africa.
It was previously thought that two flights that arrived from South Africa on Sunday had brought the first cases of the variant to the Netherlands.
Fourteen people on the flights to the capital, Amsterdam, tested positive for Omicron, among 61 passengers who were found to have coronavirus.
However, while the two new samples reveal Omicron was in the Netherlands earlier than thought, they do not predate the cases in southern Africa. The variant was first found in a specimen collected on 9 November, according to the World Health Organization (WHO). Related Posts
Early evidence suggests Omicron has a higher re-infection risk. But scientists say it will take about three weeks before it is known how the heavily mutated variant impacts on the effectiveness of vaccines.
The United Kingdom HSA said it was developing a rapid new genotyping test to allow local labs test specifically for omicron without the need for full sequencing, but could not say how widely it would be rolled out, or when it would be available.
Full sequencing can take up to 48 hours, so if samples must be sent away to be checked, it is possible that people will not know they need to self-isolate in time.
However, although cases are rising in South Africa, which experts suspect is being driven by omicron, in Botswana cases are falling, even though cases were detected there from mid-November.
A further nine cases of omicron were identified in England on Wednesday, taking the total in the country to 22. The variant has now been found in the East Midlands, East of England, London, South East and North West.
A further case was also reported in Scotland, bringing the total to 10.
President Joe Biden has backed off travel quarantine to combat the omicron variant, as the US announced tougher pre-departure testing for all passengers.
The US administration is expected to announce on Thursday that it will require all passengers to present either a negative antigen or PCR test taken within one day of their departure for the US irrespective of whether they are vaccinated or not.
The move follows the US recording its first case of omicron with a fully vaccinated American in California who tested positive seven days after returning to the US from South Africa on November 22.
The new regime reduces the time allowed for pre-departure testing from the current 72 hours for jabbed passengers, which could increase costs if they have to request accelerated results.