Health authorities are watching Victoria’s coronavirus infections “hourly”, fearing this week’s surges might signal the start of a second wave.

The state reported 13 more COVID-19 cases on Friday – taking its confirmed infections to more than 80 higher than a week ago (one case was reclassified, meaning Victoria’s official virus numbers rose by 12).

Friday’s tally came after 18 cases on Thursday and 21 on Wednesday – a six-week high.

State Transport Minister Jacinta Allan said health authorities were monitoring coronavirus data “on an hourly basis”.

However, she said there had been “no change of advice” and “no reconsideration” of coronavirus restrictions due to ease on Monday.

“If that changes there will be a very rapid response to the Victorian community,” she said.

• See the latest on Victoria’s coronavirus restrictions here

Four of the new confirmed infections are in a cluster linked to the Stamford Plaza, a Melbourne hotel that is accommodating returned travellers.

A worker from the hotel tested positive last Wednesday. That cluster has seven confirmed infections.

“The seventh case is an existing case previously linked to another outbreak related to a family in the south-eastern suburbs. Extensive investigations yesterday revealed that a personal linked to that case is also a security guard at the Hotel Stamford,” deputy chief health officer Annaliese van Diemen said.

“It’s not good news we have the outbreaks but reassuring to know there is a clear source for that particular outbreak.”

She said more cases “won’t be a huge surprise” in the Stamford Plaza outbreak.

Another new case is in hotel quarantine, one is being investigated and seven were picked up through routine testing.

Ms Allan said Victoria tested nearly 15,000 people for the virus on Thursday. Since the outbreak began, the state has tested 635,897 people.

“We’re keeping a really close eye on the numbers,” she said.

“If there’s any change to those restrictions, we’ll give that information to the Victorian community as quickly as we possibly can.”

Gyms, cinemas, indoor sports centres and concert venues are scheduled to reopen on Monday while cafes, restaurants and pubs will increase capacity from 20 people to 50.

Earlier this week, Victoria’s chief health officer, Brett Sutton, said the increase in cases with no known source of infection “could make him nervous”.

“It’s an indication that there’s still community transmission going on in Victoria,” he said.

“That’s why we need to watch it very closely and that’s why we always need to caveat what our next steps are with, ‘it depends on how things are going’.”

On Thursday, Dr van Diemen said authorities still planned to relax restrictions on Monday. But she warned it was no certainty.

“A lot can happen in five days,” she said. “We don’t want to take any chances and if it does continue to climb, we will be taking all of that into account when we decide whether or not to ease further on Monday.”

On Friday, she said authorities were remaining vigilant.

“Today’s numbers are less concerning probably than yesterday’s,” she said. “It’s cases we don’t have known links to that are the biggest concern. There a few of those.”

Westmead will lead the NSW arm of the international drug trial. Photo: AAP

NSW eyes Victoria nervously

Victoria’s coronavirus spike is also causing concern elsewhere in Australia.

On Friday, NSW Premier Gladys Berejiklian rejected any suggestion of restricting movement between NSW and Victoria, labelling domestic border closures “artificial”.

“There could be unexpected spikes and that’s the nature of a pandemic. I don’t begrudge the Victorians that – it’s not a reason to close borders with them,” she said.

NSW had seven new COVID-19 infections on Friday, but all were in people in hotel quarantine.

It came as 500 frontline healthcare workers across the state joined an international trial of a tuberculosis vaccine’s success in halting coronavirus transmission.

The NSW Health Services Union tipped $350,000 into the trial, which will examine if the BCG anti-tuberculosis vaccine can reduce the impact of COVID-19.

“This virus is not going away any time soon so until we have a proven vaccine, trials like this alongside daily testing and COVID-safe behaviours are vitally important,” NSW Health Minister Brad Hazzard said.

The trial was launched at the Children’s Hospital at Westmead on Friday, by the Bill and Melinda Gates Foundation, NSW Health and Murdoch Children’s Research Institute.

It also has the backing of the World Health Organisation.

South Australian venues are open to more people from Friday. Photo: AAP

SA to Queenslanders: Come on in

South Australia is throwing open its borders to people coming from Queensland.

Premier Steven Marshall said the change will take effect from midnight on Friday and means anyone coming from Queensland will no longer be required to spend 14 days in quarantine.

The decision follows the state’s move earlier this week to lift coronavirus restrictions on people coming from Western Australia, Tasmania and the Northern Territory.

Mr Marshall said South Australia would continue to take a staged approach in regard to other jurisdictions, including Victoria and NSW.

SA has already said it will allow unrestricted travel for people from those states from July 20.

“Our legal advice is very clear, that we shouldn’t be unnecessarily detaining people without due cause,” he said.

“There is no due cause for citizens coming into South Australia from Queensland.”

In other changes from Friday, South Australia’s pubs, clubs and restaurants will be allowed to cater for up to 300 people at a time.

-with agencies