Classified by Victorian health authorities as "community transmission", they are cases where, despite the efforts of contact tracing teams over several days, or sometimes weeks, they cannot trace the infection back to the "index case" or original source.
Melbourne, Australia's second-largest city, is now under a reimposed six-week stay-home order, however it has actually been having a hard time to check COVID-19 Record varieties of brand-new infections of the infection that triggers the illness were reported recently, triggering cautions of more constraints.
Victoria has recorded 397 new cases of coronavirus and a further three deaths, highlighting growing concern for "mystery cases" that cannot be traced to an original source.
Victoria's premier Daniel Andrews warned restrictions are likely to be extended beyond that initial six-week period - saying, "these numbers are still far too high and we could not open up with these numbers".
Andrews on Saturday announced another 397 new coronavirus infections, and expressed deep concern about the number of mystery cases it couldn't trace to a known outbreak. Check your state's restrictions on gathering limits.
"That can mean there are many more than 49 out there that have very mild symptoms or no symptoms at all", he said.
Supermarkets will remain open, and restaurants, already closed for dining in, will be able to continue with their takeaway and delivery services. According to Prime Minister Scott Morrison, the flare-up of the virus in Sydney is under control, but the spike in cases in Melbourne remains a challenge.
Australia's Health Minister Greg Hunt said at a televised briefing the federal government supports the measures with a "heavy" heart.
He added that authorities are aware of potential "unfortunate consequences" of further restrictions on settings which are not contributing to the state's harrowing surge in coronavirus cases.
Australia has fared far better than many other countries in keeping the coronavirus from spreading, but at a high economic cost.
There are now 5,919 active cases in Victoria, 95.8% of the nation's total. Meanwhile, the rest of the state will be placed under the stay-at-home restrictions that metropolitan Melbourne is now under.
Mr Andrews said he didn't want to give airtime to people trying to make political points about something they read on an obscure website. Mask-wearing has been made mandatory in the state.