The Australian city of Brisbane started an instant three-day blockade after a cleaner in its hotel quarantine system was infected with coronavirus.
Health officials said the cleaner had the UK’s highly transmissible variant and feared it could spread.
Brisbane has seen very few cases of the virus besides travelers quarantined since Australia’s first wave last year.
It is the first known case of this variant that enters the Australian community outside the hotel’s quarantine.
The blockade is for five populous municipal areas in the state capital of Queensland.
Premier Annastacia Palaszczuk announced the measure on Friday morning, local time, about 16 hours after the woman tested positive.
Ms. Palaszczuk said the blockade aims to stop the virus as quickly as possible, adding: “Doing three days now can avoid doing 30 days in the future.”
“I think everyone in Queensland … knows what we are seeing in the UK and elsewhere around the world are high infection rates for that specific strain,” she said.
“And we don’t want to see this happening here in our big state.”
Australia has reported 28,500 coronavirus infections and 909 deaths since the pandemic began. In contrast, the USA, which is the most affected country, has registered more than 21 million infections, while almost 362,000 people have died from the disease.
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The blockade will begin at 18:00 on Friday (08:00 GMT) in the city of Brisbane, Logan and in the local government areas of Ipswich, Moreton and Redlands.
Residents will only be able to leave home for certain reasons, such as buying essential items and seeking medical attention.
For the first time, residents in these areas will also be required to wear masks outside the home.
Australia faced sporadic outbreaks last year, with the most serious in Melbourne causing a blockade for almost four months.
An outbreak before Christmas in Sydney caused a new alarm, but aggressive testing and contact tracking kept the number of infections low. The city registered four local cases on Friday.
Prime Minister Scott Morrison’s government promised to start mass vaccination in February, instead of March, as planned.
Blockade interrupts ‘almost normal’ life in Brisbane
Simon Atkinson, BBC News in Brisbane
At 8:00 today, I went to the local supermarket to buy bread, milk – and how is summer here – a mango. I was practically the only customer.
When I passed the same store a few hours later, it was a different story – 50 people standing in the drizzle – lining up to enter while others emerged with shopping bags full. “Much busier than at Christmas,” a cheerful tram attendant told me. “It’s off the scale.”
Despite the “do not panic” messages from the authorities, images on social media show that it is a pattern that is repeated throughout the city.
Although stoppages are common around the world, the sudden and difficult order to stay home for Brisbane has caught people in turmoil here, after months of near-normality.
But while such a fast and stiff lock on the back of just a single Covid-19 box seems crazy in some parts of the world, I haven’t found many people complaining.
And I don’t think it’s just because Australians love to follow a rule. This is the first time that the UK variant of the virus has been detected in the Australian community.
And nobody here wants Brisbane to experience what Melbourne suffered last year. Even if it means being sleeveless.