This is the news no one wants to hear – but it's important.

We always knew there would be cases and clusters. We have plans and systems in place to deal with precisely this scenario – and those are already well underway.

But I just wanted to give everyone a quick update and make sure you've all got the most up-to-date info – and what will change as a result:

As of this afternoon, there are 8 locally acquired cases in Victoria.

All 8 are safely isolating, as are their close contacts.

The public health team worked through the night to track their movements and get a list of exposure sites together.

This is live on the DHHS website and will be updated frequently, so please take a couple of minutes to have a look.

If you visited any of the locations listed you'll need to get tested as soon as possible and isolate until you get your results. Please don't delay it.

That's the nuts and bolts of where we're at.

Here's what's happening next:

As of 5pm this evening some new measures will be in place to make sure everyone stays safe tonight – and in the days to come.

The private gathering limit will be reduced from 30 to 15.

That means a maximum of 15 guests in your home, not including babies under 12 months.

The situation in NSW is changing fast.

Case numbers are continuing to grow. There are still missing links in the chains of transmission, which suggests there'll be more cases out there that the authorities are yet to find.

Without mandatory masks and stay at home orders across Sydney, we do not have confidence that the situation remains safe.

That's why from 11:59pm tonight, the Greater Sydney area and the Central Coast will be designated a 'red zone'.

People who live in these areas or have visited since 11 December cannot enter our state.

Anyone from the red zone found trying to enter Victoria in breach of these orders will be subject to mandatory 14-day hotel quarantine.

For Victorians currently in Greater Sydney or on the Central Coast, you'll have until 11:59pm on Monday 21 December to return home.

You'll need to register for an exemption on the Service Victoria website and get tested within 24 hours of your return.

You'll then need to self-quarantine at home for 14 days from the date you were last in a red zone.

DHHS teams will be checking on people to make sure they have everything they need – and to make sure they're at home.