Victoria has reported a record 288 coronavirus cases in the past 24 hours, prompting the state to ask everyone who leaves home in Melbourne to wear a mask.
Victoria has now recorded 1600 new cases in 16 days, and here is evidence the virus outbreak in Melbourne has spread. Canberra has five cases diagnosed in the last few days sourced in Melbourne. NSW reported its first case on Friday, in a man who had towed his caravan from Melbourne and was staying in an unnamed caravan park in the Sutherland shire south of Sydney's city centre. Albury on the border has three.
Sydney authorities also linked two cases to the Crossroads Hotel in Casula. The separately diagnosed pair, a woman in her 30s and a man in his 50s, were both at the pub on Friday July 3. The hotel has been closed and a testing and tracing operation has started.
The Victorian government is distributing one million single-use masks to Melburnians. Premier Daniel Andrews said he was also having two million reusable masks made.
Mask wearing is not compulsory, but Melburnians are being asked to wear them when they are outside, especially on public transport, in shops, taxis, ubers and other areas where they cannot maintain a 1.5 metre distance from others.
Victoria's chief medical officer, Brett Sutton, said until the past couple of weeks the evidence on masks had been ambivalent. But a big meta-analysis in the Lancet journal had shown across a number of studies that masks made a significant difference, even when not worn perfectly.
"When they are worn very broadly across a population where people can't distance that 1.5m then they can make a difference, they can reduce transmission by up to two-thirds," he said.
"That's a really important addition measure and we are trying to do absolutely everything in Victoria to drive transmission down, it's a really important additional tool."
Professor Sutton said the Victorian case tally on Friday was "a pretty ugly number", but numbers were expected to plateau next week.
The 288 cases follows 165 reported on Thursday, and 134 and 191 on the days before that. The number has doubled in just four days.
Mr Andrew said no-one should underestimate how big a challenge Melbourne faced.
"It is very significant. That's why each of us have to play a part. So I know and understand there will be concern across the community to see that number," he said.
But he said Victoria was doing more testing than ever by a massive margin and case numbers were "always going to get worse before it got better".
Forty-seven people are in hospital in Victoria and 12 in intensive care. Professor Sutton said the number was "not insignificant".
"The ICU numbers have gone up significantly and the hospitalised numbers have gone up significantly," he said, warning they would rise still more as hospital numbers lagged case numbers by a week or more.
"We will see an increase in hospitalised and ICU cases and in deaths in the coming days because of the spike we have seen in recent days. It is not because the virus is worse, it is because we're seeing people who are most vulnerable," he said.
"We need to turn this around because there are places in the world that are about to be overwhelmed in their ICU capacity."
The biggest one-day tally around the country was March 28, when 469 cases were reported nationwide.
The Queensland border opened on Friday to people from jurisdictions other than Victoria, but Tasmania pushed back plans to open its border. It had planned to open on July 24, but says it will wait another three weeks at least, given the VIctorian outbreak.
NSW Health Minister Brad Hazzard praised the man diagnosed in the caravan park for coming forward, but said people from Victoria should go home to avoid being the person who seeded a NSW outbreak.
"I suggest you pack up your caravan, pack up your tent and head home to Victoria," he said. "Please go home as soon as is reasonably practicable."
Canberra infectious disease expert Peter Collignon said Melbourne had shown evidence of community transmission since early May, albeit in small numbers.
"Melbourne is a worry because the numbers are big, but if you plot it as community transmission it's much higher than it was in March and April. Most of [the earlier cases] were from cruise ships returned travellers and their immediate contacts. So this is much more of a concern. It's in the community and it's transmitting."
Professor Collignon said it was not too late to get the Melbourne outbreak under control but it was more difficult in winter and would depend on stopping people gathering indoors.
"This is mainly spread by droplets and when you're inside. If we can stop people being close together in large numbers inside we should be able to get the effective reproduction number under one," he said.
But Professor Collignon said he was concerned for people who lived alone in a six-week lockdown. The pandemic would remain for 18 months or more and Australia had to work out a way to keep transmission down while not cracking down so hard that people stopped complying.
"One of the questions we're going to have to ask is what's sustainable over the next year or two or even more - so you get the R number below one, but you get ongoing compliance. I don't know what the answer is," he said.