Omicron case with no known travel link detected in England
At least one case of the Omicron coronavirus variant has been detected in England that is unrelated to travel, according to people with knowledge of the matter, providing further evidence of community transmission in the UK.
The Scottish government earlier this week said nine cases had been linked to a single private event without any known travel connection.
Officials have so far been unable to link the English case to any travel history related to southern Africa, where the strain was first detected, whether directly or through contact with another traveller, the people said.
Meanwhile, dozens of new Omicron sequences were being assessed by health officials, suggesting the case tally will increase in the coming days. The UK has severely limited travel to and from 10 countries in southern Africa.
The UK Health Security Agency on Thursday confirmed seven further cases in England, bringing the total number of Omicron cases reported so far to 29. In Scotland, health officials have found 13 infections caused by the new variant. The UKHSA did not respond to a request for comment on the case of community transmission in England.
Nicola Sturgeon, Scotland’s first minister, said on Tuesday that what was known about the first cluster of nine Omicron cases in the country suggested there was already “limited” community transmission of the variant.
The World Health Organization last week designated the variant as one of “concern” after a sharp rise in Omicron cases in South Africa. It said on Wednesday it had been detected in at least 23 countries, adding it expected that number to rise.
Scientists are alarmed by the variant, fearing its high number of mutations could allow it to spread faster than the currently dominant Delta variant and bypass the immune protection provided by vaccines or prior infection. Studies are under way to understand this. It is also not yet known whether Omicron alters the severity of Covid-19 infection.
One person with knowledge of the English cases added it had been difficult to trace contacts in certain instances, as some of those whose Omicron infection had been confirmed left the country shortly afterwards while some also ignored isolation.
Separate testing data, analysed by government science advisers, has given an early indication that Omicron may be more widespread in England.
On account of a genetic quirk, Omicron can be picked up by a certain type of PCR test, which is used in around half of the community tests performed.
Omicron does not possess one of the three coronavirus gene targets — the S gene — analysed by commercial detection kits, giving epidemiologists an insight into its spread without the need for genomic sequencing.
Surveillance data in England showed that the proportion of Covid-19 cases with an S-gene dropout jumped from a background level of 0.06 per cent between August and October to around 0.3 per cent, as of November 28.
However, health officials are cautious about over-interpreting the recent rise because suspected Omicron cases may be preferentially put forward for S-gene testing.
Mark Woolhouse, professor of infectious disease epidemiology at Edinburgh university, said the signal had proved “extremely helpful” for showing a surge in Omicron cases in South Africa.
“In South Africa they are now picking up many more cases without an S-gene since Omicron was first detected,” said Woolhouse. “From their experience we would associate this pattern with a rise in Omicron.”
The Alpha variant, which was dominant in the UK until mid-May, also had the same genetic quirk.