Melbourne is entering their fifth lockdown. Here's what you need to know.

Victoria will enter their fifth lockdown since the pandemic began, and third lockdown this year, from midnight tonight. 

It comes as the state has recorded 18 positive cases of the COVID-19 Delta variant, with two different outbreaks that both leaked from Sydney.

On Thursday afternoon, Victorian Premier Daniel Andrews confirmed the "hard lockdown" will last for five days, until next Tuesday. 

It comes after it was announced late on Wednesday that anyone aged over 12 will be required to wear a mask in all indoor settings, including schools and workplaces, unless an exception applies. Masks must also be worn outdoors when social distancing isn't possible.

Here's everything we know about the lockdown, and the two separate chains of transmission emerging in Melbourne.

Victoria's lockdown. 

All of Victoria will go into a five-day lockdown from midnight tonight, until midnight next Tuesday. 

Mr Andrews has said it is possible regional Victoria will be released from lockdown before next Tuesday, depending on if any positive cases are recorded in the regions in the next few days.

For everyone in Victoria, there will be five reasons to leave home: shopping for food and supplies, authorised work and study, care and caregiving, exercise, and getting vaccinated.

"This will be a hard lockdown, similar to or identical to, what we did a couple of weeks ago," Mr Andrews said.

"If you were authorised to work then, you will be authorised to work now. If you were closed then, you will be closed now.

"It is essentially a repeat of the successful strategy from couple of weeks ago.

"That was successful then and this will be successful now."

How did this latest outbreak in Melbourne start?

Victoria has recorded 18 positive COVID-19 cases, with more than 75 exposure sites listed by the VIC Health. The state is dealing with two separate outbreaks, both of which originated from Sydney.

One chain of community transmission started with a family of four who returned from NSW on a red zone permit and broke quarantine requirements. The family of four have all since tested positive to the coronavirus. A man from the family visited Craigieburn Coles on Saturday whilst unknowingly infectious and bumped into a friend while at the supermarket, who has since tested positive.

The other chain of transmission started with three Sydney removalists who arrived in Melbourne on July 8 on a special workers permit.

The removalists visited the Ariele Apartments complex at Maribyrnong, which has since been plunged into lockdown for 14 days. CCTV footage shows the removalists were not wearing masks while on the job, which is a breach of the conditions of their worker permits.

Four people at the apartment block have tested positive to COVID-19, as well as the parents of a 60-year-old resident and also a personal close contact of one of the other residents.

Police drive past the entrance of the Ariel Apartment complex on July 14, 2021 in Melbourne, Australia, Image: Getty. 

The 60-year-old man attended an AFL game at the MCG on Saturday, July 10, with his friend, a teacher from Bacchus Marsh Grammar school who lives in Barwon Heads. The teacher and two of his family members - a nine-year-old child and a man in his 60s - have subsequently tested positive.

On Thursday, it was announced there were three more positive cases who appear to have contracted the virus on level two of the MCG member’s reserve, where the Maribyrnong man was. The two positive cases are not known to each other and officials are calling it an example of "stranger-to-stranger transmission". 

There are now 1500 primary close contacts and 5000 secondary contacts who are self-isolating in Victoria. 

"This is probably the fastest response we have ever seen to an outbreak that's moving more quickly than we have ever seen in Victoria, or I suspect anywhere else in Australia," COVID-19 Commander Jeroen Weimar said on Thursday.

To check the exposure sites in Victoria, you can visit here. 

Feature image: Getty.