Victoria will go into a tough “circuit-breaker” lockdown at midnight on Friday as authorities try to stamp out a worrying COVID outbreak.

Premier Daniel Andrews announced the five-day lockdown on Friday afternoon.

“Because this is so infectious and is moving so fast, we need a circuit breaker,” he said.

“People, Victorians, know what to do, and they know that these tactics, this type of response, works.”

The announcement of the five-day lockdown, which applies to the whole state, came after a crisis cabinet meeting earlier on Friday.

It followed the expansion of the coronavirus outbreak associated with a leak from the Holiday Inn quarantine Hotel at Melbourne Airport. It had grown to 13 infections by Friday morning – all workers, former guests and their close contacts.

But Mr Andrews said the “hyper-infectious” British strain associated with the outbreak had prompted the call to a snap lockdown.

“We are having cases test positive – and … by the time we find that case as positive, they’ve already infected their close contacts. Their family. People they live with, people they’ve spent time with,” he said.

“That makes it incredibly difficult, incredibly difficult to do contact tracing, because there is no gap between when we have the first case and their close contacts and potentially others that they have spent time with.”

He said Victorian authorities believed there were more as-yet undetected cases in the community.

“It is the advice to me that we must assume that there are further cases in the community than we have positive results for, and that it is moving at a velocity that has not been seen anywhere in our country over the course of these last 12 months,” Mr Andrews said.

Lockdown restrictions to apply from midnight Friday:

• Only four reasons to leave home: Shopping for necessary goods and services; care-giving; work or education that can’t be done at home; two hours a day of exercise;
• Stay within five kilometres of home;
• Masks mandatory everywhere, except at home;
• No visitors to private homes, no public gatherings;
• Schools to close, but remain available Monday-Wednesday;
• Higher education closed;
• Places of worship closed, religious ceremonies banned;
• Non-essential retail closes, hospitality restricted to takeaway only;
• Australian Open to continue, without crowds;
• Other sports events, including AFLW matches, will also continue without crowds.

Tweet from @DanielAndrewsMP

“I am confident that this short, sharp circuit-breaker will be effective. We will be able to smother this. We will be able to prevent it getting away from us,” Mr Andrews said.

“I want to be here on Wednesday next week announcing that these restrictions are coming off, but I can’t do it on my own. I need every single Victorian to work with me, and with our team, so that we can run this to ground and we can see this strategy work, just as it has worked against this UK strain in Brisbane and in Perth.”

• See an updated list of Victorian exposure sites here

Victorian health authorities declared a health alert for all of Terminal Four at Melbourne Airport on Friday. It came after a worker at a cafe at the airport was one of the confirmed positive cases on Thursday night.

Victorian testing commander Jeroen Weimar said that was the current case of most concern – although the worker “did everything right”.

“Our call to action here is now that anybody who was at Terminal Four between 4.45am on Tuesday, February 9, until 2pm, you must isolate. You must get tested. You must contact us. And stay isolated for 14 days,” he said.

“It’s critical that we run this to ground now, that we stop it here.”

Earlier, there were fears the virus outbreak might have spread interstate due to the link with the cafe worker in the busy terminal.

NSW Health has already issued similar orders for anyone who was in the terminal during the critical period.

There are now 19 active coronavirus cases in Victoria, including the 13 from the Holiday Inn cluster. More than 24,000 tests were conducted on Thursday.