The UK has reported its first cases of the new Omicron coronavirus mutation as the variant continues to spread in Europe and scientists race to assess the new level of risk.

The UK health department said one case had been identified in Chelmsford and a second in Nottingham. They were linked and connected to travel to Southern Africa, officials said.

News of the UK infections came as the WHO urged a restrained approach to the variant to ensure that countries reporting cases were not penalised.

Sajid Javid, secretary of state for health and social care, said the government had discovered the two UK cases thanks to world class genomic sequencing. “We have moved rapidly and the individuals are self-isolating while contact tracing is ongoing,” he said.

There will be a surge in testing capacity in affected areas and new travel restrictions, which from Sunday will apply to a further four African countries.

“We will not hesitate to take further action if required,” Javid said.

Dr Jenny Harries, chief executive of UKHSA, added that the agency was continuing its efforts “to understand the effect of this variant on transmissibility, severe disease, mortality, antibody response and vaccine efficacy”.

Confirmed cases and contacts were being asked to isolate and get tested.

The latest development was “a stark reminder that we are not yet out of this pandemic,” Javid said, adding that “getting the vaccine has never been more important”. 

Prime minister Boris Johnson will hold a press conference at 5pm on Saturday alongside the government’s chief scientific adviser, Sir Patrick Vallance, and chief medical officer Chris Whitty.

On Friday, the WHO designated Omicron a “variant of concern,” skipping the intermediate “of interest” designation.

Results of tests to gauge Omicron’s response to vaccines and immune systems are not expected for two to three weeks, scientists and officials said.

Global travel has increasingly been limited since Thursday, with the US, the EU, Switzerland and the UK imposing restrictions on journeys to southern Africa and a number of other countries where the variant has been detected.

South African scientists are sending samples of the virus to biosecurity agencies worldwide, including the UK’s Health Security Agency and the government’s Porton Down lab.

Whitty said the UK would “continue to work closely with the international community to quickly gather and analyse information on this variant to understand any possible increase in transmissibility or resistance to vaccines.”

Meanwhile, there was further evidence that the new variant is seeding in Europe as the first cases were identified in Germany and the Czech Republic, a day after a case was identified in Belgium.

Authorities in the Netherlands were investigating whether 61 people who tested positive for Covid-19 after arriving on two flights from South Africa on Friday had contracted the Omicron variant.

They have been placed in seven-day hotel isolation, according to Dutch health authorities.

“The positive test results will be examined as soon as possible to determine whether this concerns the new worrisome variant,” the Dutch health authority said.

Omicron appears to be behind a significant surge in cases in South Africa. Its heightened transmissibility has not yet been confirmed, though the WHO has said it appears to have a growth advantage.

Some of its mutations have been previously associated with immune escape. Any variant significantly more transmissible than Delta, already more contagious than the ancestral coronavirus, or able to pierce vaccine protection could seriously hamper the global recovery from the pandemic.

Additional reporting by Mehreen Khan

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