Health chief: "Relatively flat" virus cases in past week

The coronavirus infection rate in Australia's hard-hit state of Victoria has been "relatively flat" in the past week, the state's senior health officer said on Friday.

Victoria registered 450 new cases and 11 deaths on Friday, down from a record 725 infections recorded last Thursday.

Chief Health Officer Brett Sutton described the latest tally as "reasonable," noting that numbers would fluctuate due to laboratory processes.

"The trend overall is that we're kind of sitting at 400 to 500 cases a day. That is relatively flat over the last week," Sutton said.

A Melbourne University epidemiologist said mandatory mask-wearing had started curbing the spread of the virus.

The infection rate began to plateau at the end of July, a week after Melbourne residents risked fines if they left home without a mask, the epidemiologist said.

Victoria Premier Daniel Andrews said almost one-third of the latest cases, 139, were health care workers.

"Our nurses, doctors, ambulance paramedics, cooks, cleaners, orderlies, ward clerks, everybody in our hospital system, they are not the front line, they are the last line of defense. And I would just ask all Victorians to follow the rules to protect themselves but also to protect our dedicated health care team. They are heroes," Andrews said.

Tougher lockdown restrictions came into force in Melbourne on Thursday for the next six weeks.

Meanwhile, Australian Prime Minister Scott Morrison said it's not known when a vaccine will be found, but said his country was positioning itself well to be able to manufacture and supply a vaccine if and when it's developed.

"There are many projects that are underway around the world and we have a process for identifying those that we believe we can take an early position on," Morrison told reporters in Canberra.

Any vaccine must be shared worldwide, he added.

"Any country that were to find this vaccine and not make it available around the world, without restraint, I think would be judged terribly by history," Morrison said.

He also said Australia's borders will remain closed for international visitors.