The Delta coronavirus strain that originated in India has now been detected in Melbourne, Victoria's Chief Health Officer says.
Victorian state chief health officer Brett Sutton receives the AstraZeneca Covid-19 vaccine. Photo: AFP
Brett Sutton said the Indian variant known as the Delta strain had been identified in cases that were "unrelated to all of the other cases in our cluster thus far in Melbourne".
He said the variant was "infamous" in India and the United Kingdom.
"It is a variant of significant concern," Professor Sutton said.
"It spread extremely rapidly across India, it's become the predominant variant, indeed almost the exclusive variant there, and in surrounding countries."
He said authorities had been unable to closely link the cases to other Delta variant cases previously sequenced from hotel quarantine systems across Australia.
Victorian health authorities were working with their counterparts across New South Wales, the ACT and the Commonwealth to try to check the sequencing against any positive cases that had recently come into their care.
"We will look at all other sequences, re-sequenced to the fullest extent possible across Australia to see if there are any potential linkages to known cases and that includes those who have come through formal quarantine but also anyone else, maritime, airline, diplomatic," Professor Sutton said.
Australia's Chief Medical Officer Paul Kelly said there had been a community case of the Delta variant before in Australia, in a male from New South Wales six weeks ago.
The Delta strain was detected last night in Victoria among members of a family that travelled from Melbourne to parts of New South Wales, including Jervis Bay and Goulburn.
Several service stations in Wallan, Euroa, and Glenrowan, where the family stopped on 24 May en route to New South Wales are listed as exposure sites.
The possibility that the family picked up the Delta strain while in New South Wales has not been ruled out.
"Five or six days [of incubation] does put it potentially in New South Wales, Jervis Bay territory or indeed earlier, back in Victoria," Professor Sutton said.
Health officials were working under the theory that the virus was spread between a child from that family and another child at their school in North Melbourne.
"We suspect so, but we need to look further, but that's the likely transmission at the moment," Professor Sutton said.
It's believed one of the parents of the West Melbourne family is the index case in the Delta outbreak, which has now been linked to seven cases across two families.
Another child has also returned an indeterminate test result, but could be confirmed later as a positive case.
Vaccine efficacy against Delta strain remains unclear
Professor Sutton said there was anecdotal evidence that the Delta strain may be both more transmissible in children, and lead to a greater severity of illness in children.
The Australian Health Protection Principal Committee, which is comprised of Australia's Chief Medical Officer, and his state and territory counterparts, has met to discuss the emergence of the Delta variant in the community.
Professor Kelly said there was some evidence that vaccines may not be as effective against the Delta strain.
"There's some preliminary work out of the UK, where they have been seeing this variant, which suggests that there may be a lower efficacy of AstraZeneca but it's not zero," he said.
A temporary travel ban on Australians returning home from India was imposed on 30 April, in response to the growing number of Covid-19 cases in India, but has since been relaxed.
Prime Minister Scott Morrison said the pause did the job it was designed to do.
"The India pause proved very effective, it came at exactly the right time and its intent was to prevent a third wave in Australia, and while we have a challenge in Victoria, it wouldn't be described in those terms," he said.
"That pause has seen the effect of reducing both the number of cases that have been presenting in quarantine and the caseload of cases in quarantine came down dramatically."
- ABC