That equates to 42 people for whom the infection source could not be traced, a higher number than in any seven-day period over the course of the pandemic.
These figures are based on the last seven days for which there is detailed data, but the health department sometimes revises down the number of suspected community transmissions if further investigation by contact tracers is able to establish a link to a known case.
Evidence of ongoing community transmission indicates the virus is circulating in the community, and that it could lead to cases increasing from just a handful to hundreds within a few weeks, according to University of Sydney Professor Adam Kamradt-Scott.
“We are in a dangerous situation,” said the control of infectious diseases expert.
“This is a global pandemic. We know precisely what happens if this virus starts to spread. It is highly infectious. It’s lethal and we will see potentially large numbers of people die, like we have seen in other countries with advanced healthcare systems.
“That could happen here.”
University of Melbourne epidemiologist Professor John Mathews said many of the infections during the initial peak of the pandemic were traced back to cruise ships and returned travellers, but now Victoria was seeing an alarming rise in community transmission cases.
He called on Victorian health authorities to provide a detailed breakdown of cases according to sources of transmission, arguing much remained unknown about what was fuelling the recent spike in infections.
“We haven’t really heard from the Victorian government on precisely what they are doing about this or how they are doing interpreting the data,” Professor Mathews said.
Without a detailed analysis it is impossible to determine what proportion of people infected via community transmission were symptomatic or asymptomatic, he said.
“While it is concerning, it is quite predictable that once people thought the worst was over they stopped social distancing. The events of the last week are a signal to everybody, we can’t let up if we are going to keep it under control.”
Thirteen of the 30 new coronavirus cases confirmed in Victoria on Friday remained under investigation, with just five of the cases detected in return travellers.
Others were linked to known outbreaks, including a number of large family clusters in North Melbourne, Keilor Downs and Coburg.
A case that resulted in the closure of a McDonald’s restaurant in Mill Park now appears to have stemmed from a number of “household parties and gatherings” in Wollert, while numerous workplaces have been impacted, including a Coles distribution centre in Laverton and Orygen youth mental health facility in Footscray.
There were 183 active cases of coronavirus confirmed statewide as of Friday, bringing the total recorded overall this year to 1947.
After 10 days of double-digit growth in coronavirus numbers, Monash University’s Professor Allen Cheng said he would not be surprised to see numbers increase again in coming days as authorities embarked on “really intense tracking”.
“Hopefully some of this testing will link out some of these chains. Then we would probably be more confident to say we’ve worked out how everything has happened, and we’re probably get this under control,” the infectious diseases physician said. “But it is a pretty big job, clearly.”
Some of the government’s efforts to identify coronavirus cases had been hampered by returned travellers and Melburnians in hotspot areas refusing to get tested.
Victoria’s Deputy Chief Health Officer Dr Annaliese van Diemen revealed on Friday that 30 per cent of people in the quarantine hotels were refusing tests, along with a proportion of people who had been approached by healthcare workers going door to door in the worst-affected postcodes.
“We would like to really emphasise the message that it is important to get tested and it is important for us to find every case in those areas,” Dr van Diemen said. “We understand why people might have reservations, but we are trying to make it absolutely easy for everybody possible to get tested.”
Outgoing Chief Medical Officer Brendan Murphy said people may be kept in hotel quarantine until they agree to take COVID-19 tests.
He also said testing of people in hotel quarantine will be ramped up and regulations around hotel quarantine may be increased.
Aisha Dow reports on health for The Age and is a former city reporter.
Craig Butt joined The Age in 2011 and specialises in data-driven journalism.
Melissa Cunningham is The Age’s health reporter.