India has reported its fourth Omicron variant case as countries around the world tighten travel restrictions to contain the spread of a coronavirus strain which, experts fear, could possibly evade immunity from earlier infections.

Recently, the United States announced that new testing rules for inbound travellers will be put in place to take effect from Monday amid global alarm over Omicron variant of coronavirus. The air passengers entering the US will have to obtain a negative COVID-19 test within one day of travel.

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The requirement allows travellers to produce a negative COVID-19 test within three days of boarding their flight. US Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky’s order says all air travellers, “regardless of citizenship or vaccination status, will be required to show a negative pre-departure Covid-19 viral test taken the day before they board their flight to the United States.”

Meanwhile, Britain has also tightened its travel guidelines, requiring all travellers, regardless of their vaccination status, to take a pre-flight COVID test within 48 hours prior to their flight. The new travel rules will take effect from Tuesday.

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UK health minister Sajid Javid said that the new travel requirement will be temporary and be reviewed as the omicron outbreak develops. Both the US and the UK have allowed travellers to take either an antigen test or a PCR test.

Hindustan Times reported that Japan will add India, Greece, Romania and four US states under strict quarantine vigilance in a bid to curb the spread of Omicron. Foreigners, as well as Japanese nationals travelling from Colorado, Hawaii, Minnesota and New York, will have to mandatorily spend three days of their two-week quarantine at government-designated facilities.

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While most of the countries have reported infections in travellers from South African nations, the United States and Australia have confirmed local transmission as Omicron’s potential to evade immunity from vaccination and prior infections remains unclear.