Analysis: Melbourne’s lockdown extension gives time for experts to see full scope of cases

With the full impact of Victoria’s lockdown still not fully clear, a week-long extension buys experts time to understand how much coronavirus has infiltrated the state.

Evidence of whether Victoria’s latest Covid-19 circuit breaker was proving successful or not had barely begun to come in before the harsh lockdown was extended.

Unfortunately, the early clues that did emerge over the past three days were painting an uncomfortable picture for the state’s health chiefs.

This does present a significant silver lining for other worried Victorians though, as the major impacts of the stay-at-home orders still won’t be known for several days - increasing the likelihood they will be relaxed later next week.

With Covid-19 having an incubation period of up to 14 days, the seven-day circuit breaker was only ever intended to buy time so the chiefs could assess the effectiveness of contact tracing and whether it had built a wide enough containment line around those already infected.

Almost all the 60 cases confirmed so far would have been infected in the days and weeks before restrictions were introduced.

Evidence of whether Victoria’s lockdown has worked is still in the works. Photo by Daniel Pockett/Getty Images

But those who test positive today and over the next week would likely have picked up Covid-19 after Friday’s shut-in, so they are the cases that really matter.

As long as those cases are contained within the 5200 quarantined people who had or continue to have contact cases from before Friday, then the lockdown will have snuffed out the outbreak and Victoria can slowly move on.

In all of Australia’s previous circuit breaker lockdowns - including during Victoria’s Holiday Inn cluster - this pattern had been established in less than a week, preventing any extension.

The problem now is that while current evidence does not show the outbreak has significantly breached this contact tracing containment line, it is dangerously close.

In the past three days new cases have unexpectedly been connected to Tier 2 and Tier 3 exposure sites - the so-called ‘contacts of contacts’ identified only as an insurance buffer rather than any expectation they will actually test positive.

Mystery cases connected the Arcare Maidstone aged care home and, on Tuesday, a Melbourne family who had travelled to NSW, have also convinced health chiefs there are active chains of transmission they still don’t know about and which contact tracing cannot manage.

This saw a massive 700 new close contacts identified overnight on Tuesday - four days into the circuit breaker - dashing any hope of ending the lockdown this week.

Unlike previous circuit breakers, evidence suggests casual transmission of the Kappa Covid-19 variant is driving these few, but almost untraceable, cases.

Now we have a line on the impact of contact tracing the effectiveness of will begin to show, and the entire state will be waiting to see if it can wipe out the last remaining transmissions contact tracing cannot reach.