Australia's second most populous state Victoria will enter a seven-day lockdown to counter a fast-spreading outbreak in its capital, Melbourne.
The lockdown will begin at midnight on Thursday (14:00 GMT).
Authorities have so far found 26 cases, and identified 150 sites where people may have been exposed to the virus.
There is growing anxiety over the outbreak which reminds many locals of a devastating second wave that swept the state last year.
Victoria's acting Premier James Merlino said the outbreak involved a highly contagious strain of the virus, the B.1.617 variant. A returned traveller was infected with the strain, which Mr Merlino said was spreading "faster than we have ever recorded".
Cases have been found across the state with links to a large number of venues, including packed football games at stadiums in Melbourne.
"With 10,000 primary and secondary contacts of cases, with more than 150 exposure sites right around the state of Victoria, we need to act now," Mr Merlino said.
"If we wait too long, this thing will get away from us."
Melbourne has been there before. And this is precisely why there's a great deal of nervousness and anxiety in Australia's second city this evening as it prepares for another strict lockdown.
Photos of empty supermarket shelves have circulated on social media with someone tweeting: "Here we go again!" Others are sympathising with the city saying: "Take a deep breath Melbourne."
Compared to the rest of the world, 26 cases is extremely low - but there are a number of worrying factors.
There are 10,000 primary and secondary contacts, so there's big potential for the number of community cases to increase. The circle of exposure sites has also widened including regional Victoria which will be a big and complex job for contact tracers.
More crucially, not enough people have been vaccinated. Which has brought to light once again how slow, and frankly, at times shambolic Australia's vaccine roll out has been.
In some areas there've been complaints that people show up and there aren't enough jabs. In others the vaccines have been lying in fridges unused.
What's clear is that whatever the government has been doing hasn't worked to get more jabs in arms. There have been continued calls for a consistent and a more direct campaign about the urgency for people to get vaccinated.
For the past year the numbers have told Australia's success story in containing and for a while eliminating the virus - but the numbers are telling an opposite story when it comes to vaccinations. And all it takes is an outbreak like we're seeing in Melbourne to put that success at risk.