What we know about the Delta variant now in Melbourne

Health authorities still don’t know where the source of this variant is – Victoria, NSW or elsewhere. It hasn’t been genomically linked back to coronavirus cases in hotel quarantine.

However, as the Delta variant has spread around the world – it is now the dominant virus in Britain – it has also arrived in great numbers in Australia’s hotel quarantine system.

Data from cov-lineages.org suggests Australia has spotted the Delta variant at least 108 times so far, twice that of Kappa and more often than the Brazilian or South African variants.

The Delta strain is the second variant spotted in India – formerly known as B.1.617.2, until it was renamed this week by the WHO.

In Britain, the variant has quickly outcompeted both the Kappa variant and the well-established Alpha variant, which caused the country’s winter surge.

Evidence suggests it is substantially more transmissible than the Alpha variant, which was already more transmissible than the virus that came originally out of Wuhan.

Cases of Delta are rising in the UK even as cases of Alpha fall; it now makes up about 75 per cent of the country’s cases.

The variant lab at the Kirby Institute – seen here through thick protective glass.Credit:James Brickwood

“In the lab under controlled conditions, we do see Delta to be approximately 1.4 times fitter than Kappa,” said associate professor Stuart Turville, who is studying COVID-19 variants at the Kirby Institute in Sydney.

“Whilst this is a laboratory observation, the displacement of Kappa by Delta in India does support it to be a fitter variant in populations where vaccine immunity is low.”

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At a news conference on Friday, Chief Health Officer Brett Sutton said there were “some anecdotal reports of greater illness in children as well as greater increased transmissibility in children”.

Professor Howden said he “not aware of that evidence, to date”.

″⁣There may be increased impact in children such as transmission and disease severity, but these are only anecdotal reports and we need more data/evidence before we can draw firm conclusions regarding this”

Professor Howden said there was no possibility of mistaken identity, as the Delta variant was significantly different genetically to the Kappa variant behind Melbourne’s current lockdown.

There was also no possibility that Kappa had mutated into Delta in Melbourne, he said.

Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.

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