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More than 2,000 people, 1,600 of them children, have been put into quarantine in a Swiss district after two cases of the Omicron variant of coronavirus were detected at a school.
Geneva had previously confirmed one case in an individual who had returned from South Africa, and another suspected case linked to the same individual.
"Following two confirmed cases of the Omicron variant which attended the Châtaigneraie campus of the International School of Geneva this week, the cantonal medical services of the cantons of Vaud and Geneva have jointly taken the decision to quarantine all of the students and campus staff for ten days," Geneva health authorities said in a statement.
Switzerland has identified a handful of cases of the new variant spread across five of its 26 cantons, and imposed travel bans from southern Africa and quarantine requirements on arrivals from 23 countries including Japan, Britain and Canada.
The Swiss government said on Friday that events and venues would have the right to refuse entry to people who are not vaccinated or can't prove they have recovered from previous COVID infection.
The Omicron variant has now been identified in 35 countries worldwide and is spreading rapidly in Europe.
Authorities said 1,600 of those quarantined in Vaud and Geneva are children. Alongside students, parents and siblings are also being asked to take a test to check for the variant.
The health authority did not say whether the new quarantine measures were related to the previously confirmed case, but said the two confirmed cases were "closely related within the family to a positive person returning from a trip to South Africa."
A study of recent coronavirus cases in South Africa, where Omicron was first identified, suggests the variant has “substantial” ability to cause reinfection in people who have previously had COVID-19.
The study estimated that the risk of reinfection for 1 to 27 November, when Omicron was circulating, was 2.39 times higher than in the first wave of the pandemic in early 2020.
In contrast, the risk of reinfection in South Africa was lower in the Beta and Delta waves than in the first wave.
The findings suggest Omicron could cause a wave of infections in people with some prior immunity.
The researchers, from the National Institute for Communicable Diseases (NICD), looked at data from almost 2.8 million people with Covid-19 who had a positive test result at least 90 days before November 27.
On Thursday the European Centre for Disease Prevention and Control (ECDC) warned that Omicron could become the dominant COVID variant in Europe.
Most of the cases so far reported in Europe have some connection with southern Africa. However, some nations are beginning to report incidents of community transmission.
At least 42 cases have not been reported in the UK, with the government tightening restrictions and accelerating its booster vaccination campaign in an attempt to stem the spread.
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