New South Wales is effectively locked out of the rest of the country, as states scramble to close their borders and keep the “volatile” Sydney cluster at bay.

Medical experts have pleaded with the NSW government to take stronger actions to bolster defences against the virus – or the state risks being forced into another lockdown.

On New Year’s Eve, Victoria and South Australia announced a hard border to all of NSW, while the NT introduced a ‘hot spot’ traveller ban.

Western Australia went one step further, and locked out Victorian travellers, too.

Queensland and Tasmania already have ‘hotspot’ bans in place, but are yet to make new announcements.

As the country enters a new calendar year, pressure is mounting on NSW Premier Gladys Berejiklian to mandate masks.

Victoria on Thursday morning declared masks would now be required in all indoor situations (that aren’t an individual’s own home) and halved household visitor numbers, as eight community transmission cases were confirmed in Melbourne.

NSW recorded 28 new community transmissions cases in the 48 hours to Thursday, but Ms Berejiklian has ignored the urgent pleas from medical experts to enforce mask wearing.

• Related: See the latest coronavirus health alerts for NSW

At present, masks are recommended on public transport and in crowded indoor spaces.

https://twitter.com/drpete00/status/1344434164360044544

The Australian Medical Association’s NSW president Danielle McMullen says the state sits on the edge of a dangerous outbreak.

“We need to employ every defence we have against this and we need to do it now if we want to avoid a harsh lockdown later,” Dr McMullen said.

“Making masks mandatory sends a strong signal to the community about the importance of wearing masks to reduce the spread of the virus.

“We are teetering on the brink of an explosion of COVID-19 in NSW.”

Ms Berejiklian said her government was trying to strike the “right balance”.

Premier Gladys Berejiklian, left, has stressed the importance of wearing masks, social distancing and hand hygiene but has not mandated it. Photo: AAP

“This is a very unpredictable, contagious disease but we also appreciate that we don’t want to put more burdens on our citizens than we need to,” she said, in regards to mandating masks.

Ms Berejiklian described the situation as “volatile”.

“What is really important is for all of us to do everything we can to reduce our mobility, to reduce the number of people that we’re mixing with, and to make sure that we stick to the rules and the health advice,” she said on New Year’s Eve.

A number of restrictions were swept in earlier in the week, days out from December 31, after health authorities repeatedly expressed fears it could become a “super-spreader” event if celebrations were allowed to continue freely.

Melbourne is really stepping up in regards to COVID-19.

Just went for a walk to the shops and 90% of the people on the street were wearing masks. We haven't been told to wear masks outside.

Everyone's simply choosing to do what they can to prevent another outbreak. #COVID19Vic pic.twitter.com/NQ0Wo9n6RN

— Brad Stephenson (@Shuttlecock) December 31, 2020

You’ve got just hours to get home

As NSW’s Avalon cluster grew to 144 (at the time of writing), the rest of the country moved quickly to seal out the looming threat.

South Australia announced a hard border to the state on Thursday morning. Victoria joined just hours later – spurred on by the NSW daily report of 10 new cases of community transmission.

A hard border will be imposed with NSW. Photo: ABC

From 11.59pm on January 1, Victoria will create a hard border to all of NSW. It follows from a ban on all travellers from Greater Sydney, Northern Beaches and Central Coast.

Anyone who arrives back in Victoria from anywhere in NSW after that time will have to go into hotel quarantine for 14 days.

“This is going to cause some disruption for Victorians who may be holidaying,” Acting Premier Jacinta Allan said on Thursday.

“However these difficult decisions are about protecting the community, protecting and keeping case numbers low and doing everything we can to lock in the gains we have made over the course of 2020.”

A permit system is in place for exempt travellers.

Victoria has been warned to brace for a spike in case numbers as rigorous contact tracing and testing is rolled out across the state, in response to the new diagnoses.

An evolving list of health alerts and confirmed exposure sites is available here.

-with AAP