The Delta variant of Covid-19 has been identified in two members of a West Melbourne family who travelled to New South Wales and were previously thought to have been part of the wider Melbourne outbreak.
It came as health officials say they have no plans to end Melbourne’s 14-day lockdown earlier than planned, despite two cases of “fleeting transmission” in the state being reclassified on Thursday as false positives.
On day eight of Melbourne’s fourth lockdown, the state reported four new locally-acquired cases of Covid-19 out of over 49,000 tests, including three members of a family previously reported to have travelled to New South Wales.
The fourth case is a primary close contact of an existing case who has been isolating for their entire infectious period. Health officials are also seeking to determine whether another child linked to the family has Covid-19 after an indeterminate result was returned.
The West Melbourne family who travelled to Jervis Bay is not linked to the current outbreak, Victoria’s chief health officer, Prof Brett Sutton, revealed, splitting the seven cases associated with the cluster from the rest of the Victorian outbreak. He said genomic sequencing revealed they had the Delta variant of Covid-19, which has become the predominant variant in India, whereas the rest of the outbreak is genomically sequenced to the Kappa variant.
The source of the transmission is still unknown. Victorian health officials were attempting to link it to known cases in the state, including those who had come through hotel quarantine, or had been in Australia through the airline or freight systems.
Sutton said the working theory was the virus transmitted between two grade five students, and the Delta variant was “the most significant in terms or transmissibility”, and said there were anecdotal reports of greater illness in children and transmissibility in children.
“We’ve got concerns for that reason … transmission between children has always been known,” Sutton said. “There has been some dispute about how commonly it occurs and how likely it is in particular settings and with particular variants.”
Sutton said the new variant had been seen in hotel quarantine among returned travellers, but there had been no cases closely matching the genomic sequence in Australia.
The news came after the Victorian health department announced on Thursday evening one case of fleeting transmission from stranger to stranger at a Metricon display home at Mickleham, and an outdoor fleeting transmission at Brighton Beach Hotel were false positives, after being reviewed by an expert panel.
The admission sparked calls for the extended lockdown on Melbourne to be ended sooner than 10 June, because health officials had cited these cases of stranger-to-stranger transmission as part of the justification for the need for the extended lockdown.
However, the acting premier, James Merlino, said on Friday morning the public health advice had not changed.
“It is absolutely based on public health advice and that is assessed day by day, hour by hour … the proposition put forward by public health was that we needed this further seven-day period for greater Melbourne to absolutely run this thing to the ground,” he said. “That remains the case.”
The Victorian health department said there were still eight other cases of stranger-to-stranger transmission, including at a Telstra store in South Melbourne, two cases at a grocer in Epping, two at a GP clinic in Reservoir, two at a Woolworths in Epping North, and one at Craigieburn Central Shopping Centre.
Sutton said the decision to keep lockdown going was in part due to the fact that prior to the outbreak Victoria had very few restrictions, meaning they had more than 300 exposure sites and 6,000 contacts to track down.
“We need the time to see how that plays out” he said.
Approximately 90% of the 6,000 close contacts identified with the Victorian outbreak have returned negative results, and the chief health officer said the settings would be reviewed daily.