New cases of the Omicron coronavirus variant continued to be detected around the world on Sunday, as nations tried to delay a surge in infections by restricting travel and imposing new quarantine measures.

Omicron first emerged earlier this month in southern Africa. The World Health Organization designated it a “variant of concern” on Friday, saying it appeared to be able to reinfect patients and that it displayed mutations previously associated with diminished vaccine efficacy and higher transmissibility.

Both findings are yet to be confirmed, and it is also not yet known whether the variant alters the severity of Covid.

The United States, the European Union, the UK, South Korea and others have all severely limited travel to and from the southern African region. Switzerland has also restricted travel to non-African nations where cases have been detected.

Israel became the first country to close its borders to foreigners, with officials previously signalling they were on the verge of declaring a state of emergency. At least one case has been confirmed and several more are suspected. Returning travellers will be forced to quarantine, and the government has deployed the army and domestic intelligence agency Shin Bet to track them down.

“Everyone is tired of life in the shadow of the coronavirus,” said Prime Minister Naftali Bennett. “I hear what people are saying to me: ‘We have just emerged from the Delta strain and now a new strain has arrived?’ It is not easy but it is reality.”

European countries were racing to contain the Omicron variant amid a resurgence of cases caused by the earlier Delta variant. Dutch health minister Hugo de Jonge on Sunday said 13 Omicron cases were found among 61 passengers who tested positive for the virus on two flights from South Africa to Amsterdam on Friday. All positive passengers have been forced into hotel quarantine for seven days and de Jonge said it was “conceivable” that more Omicron cases were present in the country.

The Netherlands has imposed one of the EU’s most stringent lockdown restrictions over the past two weeks, with non-essential shops shutting at 5pm and quarantine imposed on returnees from high-risk areas.

A third confirmed case has been identified in the UK, and dozens more are being treated as suspected cases, people familiar with the matter have told the Financial Times.

Calls for renewed lockdowns are growing louder in Germany after the national academy of sciences, Leopoldina, published a paper advising the government to introduce restrictions on public and private gatherings, including for the vaccinated. Two cases of the Omicron variant have been confirmed in the southern state of Bavaria.

In an interview with Bild am Sonntag, German President Frank-Walter Steinmeier called on citizens to prevent a lockdown by voluntarily restricting their contact with others.

Saudi Arabia said via the state news agency SPA it would allow direct entry from all countries on condition that the passenger had received one vaccine dose in Saudi Arabia, and mandated a three-day quarantine for travellers.

Anthony Fauci, the US chief medical adviser, said the variant could already be present in the country. No cases had yet been detected.

The WHO has called for “balance” in the global response to the variant, saying countries should strategically deploy their testing and sequencing capabilities to counter it. The Omicron variant can be detected by proxy on routine PCR tests, as it misses a gene — S — that Alpha, a previous variant, also lacks. Genomic sequencing is needed to confirm its presence.

Since coronavirus first emerged in Wuhan, China, in late 2019, more than 261m people have been infected globally, and at least 5.1m have died, according to Johns Hopkins University.

Additional reporting by Samer Al-Atrush and Christian Davies

News