A troubling variant of coronavirus has spread in Victoria, seeping into the Australian community for the first time.
Seven cases of the variant have been identified, with four linked to a family who travelled to Jervis Bay in New South Wales.
Overnight sequencing also detected two cases in West Melbourne.
Here’s what we know about the Delta strain:
What is the Delta variant?
This is the strain that is now infamous in India and increasingly in the United Kingdom.
“It is a variant of significant concern,” Victoria’s chief health officer Brett Sutton said on Friday.
“It’s obviously a concern that it is not linked to other cases, but we are chasing down all those primary case contacts.”
What is the background of the strain?
The Delta variant spread extremely rapidly across India to become the predominant variant in that country.
“Indeed almost the exclusive variant there and in surrounding countries — Nepal, Bangladesh (and) Sri Lanka,” Professor Sutton said.
“All are also affected by a significant uptick in cases related to that variant.”
Why should we be concerned?
Very high transmissibility potential is the main concern.
There are some anecdotal reports of greater severity of illness in children, as well as the potential increase in transmissibility among children.
“We’ve got concerns for that reason,” Professor Sutton said.
Stuart Turville, from the immunovirology and pathogenesis program at UNSW Sydney’s Kirby Institute, said the number of Delta cases was increasing globally.
“Like what we have seen with Alpha in early 2021, it just means we will see more Delta cases in quarantine and that if there is a breach, it will be highly probable to be that variant,” he said.
What is the key difference between the Delta and Kappa strains?
Authorities say the Delta strain appears to move more quickly at “casual contact” sites.
“I’m not saying it has magical qualities, but we have noticed five exposure sites where transmission has occurred to seven individuals, I believe, who have had less than that usual prolonged indoor home, work, face-to-face settings, or indeed restaurant settings,” Professor Sutton said.
Dr Turville described the Delta strain as the genetic “cousin” to Kappa.
“The key difference is that it has a fitness gain that enables the virus to bind cells better,” he said.
“In the lab under controlled conditions, we do see Delta to be approximately 1.4 times fitter than Kappa.
“While 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.”
Is it surprising that the virus was possibly transmitted between two Year 5 students at school?
Dr Turville said it was something that authorities needed to keep an eye around the world.
“Viruses that increase their affinity for receptors (become more sticky) need to be looked at carefully, as this can manifest as changes in how they not only spread but also who they can infect and causes disease in,” he said.
“This needs to be documented accordingly and is best done by those compiling global observations of prevalence and disease course.
“While Delta is listed as a variant of concern, the data from vaccinated populations in the UK are promising.”
How do the viruses get their names?
The World Health Organisation recently decided to simplify the virus names with Greek numerals.
Australia’s chief medical officer Paul Kelly said this was the third attempt.
“One was where they were first being found, the second was a long series of numbers and letters, which was becoming difficult to remember — even for epidemiologists,” he said.