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People under 40 account for 55% of Victoria's Covid cases but only 6% of deaths

<span>Photograph: James Ross/EPA</span>
Photograph: James Ross/EPA

More than half of Victoria’s active cases of Covid-19 are in people aged 39 years old and younger, while less than 6% of the state’s deaths have been in the same age group, data from the Department of Health shows.

The data included all cases of the virus and deaths up to 11 August. The age group with the highest amount of active cases is 20-29 years, with 1,823 infections. There have been no deaths in the state in this age group. Four deaths have occurred in those aged 30-39, while one death occurred in the 40-49 age group. Those aged between 0 and 39 comprise 54.9% of all active cases.

Meanwhile, 103 people in their 80s and 47 people in their 70s have died. On Thursday the premier, Daniel Andrews, said of the 21 deaths overnight – the state’s deadliest 24 hours to date – 11 were aged in their 80s.

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The federal government’s Covid-19 infection control expert group chair, Professor Lyn Gilbert, said there were numerous reasons behind the significant numbers of young people with the virus. Before the restrictions and lockdown took effect, she said, “they were less likely to stay home, more likely to gather in large groups, and less likely to heed physical-distancing advice”.

She added that large families with shared child-minding arrangements had led to spread among children and teenagers. Their parents sometimes worked across multiple jobs in high-risk occupations, she added, with parents then infecting children and extended family.

“I don’t think the risk of infection is related to age, but to risk of exposure,” Gilbert said.

Infectious disease doctor and epidemiologist Professor Allen Cheng said young people often had no or very mild symptoms. This meant their cases were not always being detected. He urged young people to get a test with even the mildest of symptoms, and to stay home until they received their result. “There are a lot of cases in this younger age group, and that reinforces the need to communicate better with this group who usually have milder symptoms,” Cheng said.

Dr Ian Musgrave, a molecular pharmacologist and toxicologist with the University of Adelaide, agreed a higher level of asymptomatic spreaders in the younger age groups, who may then spread the virus to peers and siblings, needed to be factored in.

“I suspect the answer to why so many young people have the virus is complex,” Musgrave said. “Young people are involved in more service jobs where they are exposed to more contact,” he said.

“I’m pretty sure that young people aged 18 to 25 are not more susceptible to infection. This is in stark contrast to mortality, where mortality is strongly skewed to older age groups.”

He added that younger age groups were likely to have been isolating less prior to lockdown, which he said was “due in part to the widespread belief that young people don’t get Covid-19 as easily, and partly because the messaging is not reaching them”.

On Wednesday an article in the Medical Journal of Australia by Dr Zoe Hyde, from the University of Western Australia, cast doubt on the idea that children are much less susceptible to Covid-19 infection than adults and do not play a substantial role in transmission.

“However, emerging research suggests this perception is unfounded,” Hyde wrote. While it was true children overall experienced much less severe illness from the virus, Hyde said “the role that children play in transmission is less certain, but there is no reason to think that children are less likely to transmit the virus than adults”.

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It meant when cases were identified in school communities, they must immediately close, as was the case in Victoria before schools moved to remote learning.

“Schools are clearly neither inherently safe nor unsafe,” the article said. “The risk associated with these settings depends on the level of community transmission, and it must be continuously evaluated. Schools must not remain open for face-to-face teaching in the setting of ongoing community transmission.”