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Where did Australia’s first cases of the Covid Delta variant come from and how infectious is it? | Melbourne

Two West Melbourne family members who visited New South Wales last month before testing positive for Covid-19 were found to have the Delta variant of Covid-19.

It is the second time that the variant, first identified in India, has been found in the Australian community, after a Sydney couple tested positive in May.

So how is the Delta variant different from other coronavirus strains?

What is the Delta variant of Covid-19?

The World Health Organization has begun using letters from the Greek alphabet in its designation of new Covid variants, and the Delta variant, also known as B.1.617.2, is the name given to the variant first detected. time in India in October 2020.

The WHO says it has now been detected in 62 countries and is becoming the dominant variant in several countries, including Nepal, Bangladesh and Sri Lanka. In the UK it is estimated to be the variant in 75% of cases.

In Australia, the more than 60 cases of the Melbourne outbreak have been linked to the other variant first detected in India, the Kappa variant, with the exception of the two West Melbourne cases.

How did it spread to the Australian community?

In early May, a man and his wife in the eastern suburbs of Sydney tested positive for the variant, but despite the man visiting several locations, including a cinema and barbecue shops, no community spread of the virus was detected. .

Then on Friday, Victorian health authorities said the Delta variant was discovered after examining the genomic sequence of the virus detected in two cases in a family of four that traveled to New South Wales in late May. They visited Goulburn and Jervis Bay before developing symptoms and getting tested.

The variant was first detected in a fifth-grader at a school in North Melbourne, and it is likely child-to-child transmission.

There are now seven cases in two families linked to this group, after two adults and a child tested were reported as positive cases on Friday. Another child is an indeterminate case.

About 70% of the 300 identified close family contacts they have been isolating have tested negative.

The source of the original transmission is unknown. Victoria’s health director, Professor Brett Sutton, said health officials in Victoria are looking for clues, looking at sequences of the virus detected in hotel quarantine, via airlines, and via sea, diplomatic and other routes. ways people have returned to Australia.

“We have to explore all avenues,” he said. “We have to be clear about who is the first probable case in this group and then go through a really forensic process of understanding in all the places where they have been and obviously all the evidence of the people with whom they may have been in contact, including blood tests. of people have recovered from the disease “

How worrisome is it?

Honorary Principal Investigator for the George Institute for Global Health, Professor Alexandra Martiniuk, said variants are more likely to occur in countries with large numbers of cases. Martiniuk said Delta is one of four so-called variants of concern where variation increases transmissibility, increases virulence, has a more severe presentation in the hospital, or decreases the effectiveness of the public health response.

Kappa is a variant of interest, which is still more infectious than other strands, but it has not been observed to have as high a community transmission as Delta and other variants of concern.

“Delta is a more worrisome variant than the Kappa variant,” he said. “Currently Kappa is listed as a variant of interest, not as worrisome as Delta at this time.

Sutton said he was concerned about the high level of transmissibility, in addition to anecdotal reports that it was more transmissible between children than other variants.

Are people more likely to end up in the hospital?

It’s too soon to say that.

“The severity or duration of the disease compared to the ‘original’ Sars-COV-2 for the Delta variant is not yet known, [there’s] there is not enough research yet, ”said Martiniuk. “The other variants of concern are likely to have increased severity and death.”

In England, where 38,805 cases were sequenced, they found that the Delta variant was associated with a 2.61 times greater risk of hospitalization in 14 days than the Alpha variant.

Are Delta Variant Vaccines Effective?

Vaccines appear to have an impact on transmission. In the UK, 75% of Delta cases were reported to be people who were not vaccinated, and only 3.7% of people who were fully vaccinated contracted the Delta strain. 5% of those hospitalized with the Delta variant were fully vaccinated.

Australia’s chief medical officer, Professor Paul Kelly, said AstraZeneca’s efficacy against this particular variant has yet to be seen.

“There has been some work in the UK that suggests there may be less efficacy of AstraZeneca, but it is not zero and that is preliminary lab work and we have to wait for the real world experience that only comes when we have big breakouts and I I’m sure we won’t have them in Australia. “

What does this mean for the Melbourne lockdown?

Sutton said identifying the Delta variant in the community would not change plans immediately, as close contacts connected to the family were isolated and will undergo testing. But he said it was important to find the source and if there were more linked cases.

“We need to understand where it comes from. That means there are unidentified ascending cases, whether they are in Victoria or elsewhere remains to be determined. “

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