Victorians are adjusting to the news that the highly infectious COVID variant behind the wave of infections devastating India has now been detected in its recent outbreak.
Here is what we know about the Delta variant and how it came to be.
What are all these different names?
The strain that has been associated with the Victorian outbreak to date, and which first leaked from hotel quarantine in South Australia last month, is known as Kappa.
Genomic sequencing revealed this morning has shown there’s now a group of seven cases in Melbourne from another strain, called Delta.
Both Kappa, also known as B.1.617.1, and Delta, also called B.1.617.2, are considered subtypes of what’s been referred to as the Indian variant — B.1.617.
The numeric identifiers may be a bit more familiar to you, because they have been around for a bit longer.
The names Kappa and Delta that are now circulating have resulted from a World Health Organization decision to name variants of COVID-19 after Greek letters rather than the places they were picked up in.
How long have these variants been around?
Like all viruses, as COVID-19 has spread, small mistakes — or mutations — have slightly changed the virus.
Many of these changes are considered harmless, but some of the mutations can lead to variants that are more easily spread.
The Indian variant of COVID-19 was first detected in October last year and has since infected people in dozens of countries around the world.
What makes some variants more contagious than others
The virus that causes COVID-19 is evolving, with new and more infectious variants taking hold. But how do these variants occur and what makes some more contagious than others?
Other well-known variants include a UK variant that was detected in September last year, now being called Alpha, and a variant from South Africa that was detected last May that’s now being called Beta.
Three subtypes, or sublineages, of the Indian variant, including both Kappa and Delta, have spike protein mutations that have been associated with increased transmissibility.
However, much less is known about the Kappa variant because Delta has been more widespread, particularly in India and the UK over the past few months.
How infectious is the Delta variant?
Burnett Institute epidemiologist Mike Toole, who is based in Melbourne, said some key knowledge about the Delta variant had been established.
“We don’t know much about the Kappa variant because it more or less died out very quickly in India and the UK and was replaced by the Delta variant,” he said.
“So we’ve kind of lost any chance to study that Kappa variant, but we do think it was at least as infectious as the so-called Alpha variant that came from the UK.”
Dr Toole said data from the UK showed that Delta was more infectious than other variants.
“This Delta variant may be up to 50 per cent more infectious than the UK variant, Alpha, so that makes it up to twice as infectious as the original Wuhan strain which caused the second wave in Victoria.”
Professor Toole said there was also evidence that Delta spread more easily among children than other variants.
Victoria’s Deputy Chief Health Officer Allen Cheng has said another way to think about the infectiousness is the R0 value, or how quickly the virus spreads if there are no mitigating measures such as distancing, masks or restrictions.
Professor Cheng said last year’s Wuhan strain had an R0 value of around 2.5, the Alpha strain was about 3.75 and the Delta strain was about 5.
That means if we were living life like we were in 2019, one person with the Delta strain would likely infect five other people, compared to just 2.5 last year.
Deakin University’s chair of epidemiology Catherine Bennett said there was a broad consensus that the Kappa strain was slightly less infectious than the Delta strain.
“The Kappa is still one that they’re concerned about because it does actually have characteristics that are associated with these mutations to do with the spike protein that they’re worried about,” she said.
“That it could make it more likely to escape vaccine or be a bit more infectious.”
Do the new variants affect people differently?
Victoria’s Chief Health Officer Brett Sutton said evidence was still emerging about the severity of the Delta variant, but there were anecdotal reports of greater severity of illness in children compared to earlier strains.
Professor Bennett said very recent UK data suggested people were more likely to require hospital treatment when infected with the Delta strain, compared with the Alpha strain.
“You’re more than twice as likely to be hospitalised if you have that variant and 1.6 times as likely to be in an emergency department within two weeks of having an infection,” she said.
Do vaccines work against both variants?
Studies are still underway, but there is some promising evidence from the UK that AstraZeneca and Pfizer vaccines provided a similar level of protection against the Delta variant as they did against the earlier Alpha variant.
Less is known about how effective the vaccines are against the Kappa strain that is more prominent in Victoria’s current outbreak, but experts have said it’s likely to be similar to the Delta variant.