A five-day statewide lockdown for Victoria will begin midnight Friday in a bid to stop the spread of the more-infectious UK variant of coronavirus, Premier Daniel Andrews said.
The cluster, linked to quarantine hotel Melbourne Airport Holiday Inn, reached 13 cases on Friday.
Andrews said the UK strain “moving at a velocity that has not been seen anywhere in our country”, Andrews said.
“This is a short, sharp, circuit breaker.
“If we wait to be certain, it will be too late”.
Under the stage four restrictions, schools and shops will shut and Australian Open matches will be played behind closed doors.
Victorians must stay home except for four essential reasons: shopping, caregiving or compassionate reasons, essential work, and exercise.
Two hours of exercise and shopping limited to 5km from a resident’s home.
Religious gatherings and weddings are not allowed.
Tennis stars Serena Williams, Novak Djokovic and Aussie Nick Kyrgios are due to play at the Australian Open on Friday.
British scientists have said the UK variant of the virus that is behind a surge in infections there may be not only more transmissible, but also more lethal - with a mortality risk around 30% higher than other variants.
The outbreak in Melbourne, where the Australia Open tennis tournament is underway, has raised fears of a new wave of infections in the state hardest hit by COVID-19.
Victoria had more than 20,000 cases last year and more than 800 deaths, forcing authorities to impose a strict lockdown for more than 100 days, the most severe action taken anywhere in Australia.
The latest outbreak was likely sparked by a medical device known as a nebuliser being used by a COVID-positive guest at the hotel, authorities said.
Most of Australia’s eight states and territories closed internal borders in 2020 for the first time in a century to keep the virus out, but they have slowly reopened to domestic visitors as they go for long stretches without new infections outside hotel quarantine.
But South Australia, which neighbours Victoria, closed its border again this week because of the Melbourne hotel cluster. Queensland has declared greater Melbourne a hotspot.
Australia has been among the world’s most successful countries in handling the novel coronavirus, largely because of decisive lockdowns and borders sealed to all but a trickle of travellers, with some 22,000 cases and 909 deaths.
But its quarantine hotels, where all international arrivals spend two weeks, have proved to be a weak link in its defences with the cluster in Melbourne the latest to emerge from one.
With additional files from Reuters.
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