A primary school in Melbourne’s north was closed on Friday after a student tested positive for the coronavirus – sparking a warning about hot spots of community transmission in the city.

Victorian chief health officer Brett Sutton said the prep student from Newbury Primary School in Craigieburn was at school late last week, before returning a positive test on Wednesday.

The child was one of three coronavirus infections confirmed in Victoria on Friday morning.

The school was expected to reopen on Tuesday, after the long weekend.

But the prep student’s diagnosis showed there were apparently low levels of community transmission of the virus in Melbourne’s north and north-west, Professor Sutton said.

“Right from Keilor Downs through Fawkner to Craigieburn, this is where in the past couple of weeks we’ve seen community cases,” he said.

“These areas of Melbourne appear to be the hot spots at the moment and so people, really, from that inner-west to inner-north of metro Melbourne really need to consider – if they have symptoms – to get tested, to isolate if they’re symptomatic.”

In late May, Keilor Downs Secondary College was closed after a student’s positive COVID-19 test. Other students from schools in surrounding suburbs were asked to self-isolate because they were close contacts of the infected student.

Global Resource Recovery in Laverton was closed after coronavirus diagnoses in staff.

The student was among a family cluster of coronavirus cases that has also been linked to Global Resource Recovery in Laverton. The plant closed on May 29, after two employees linked to the Keilor Downs outbreak were diagnosed with COVID-19.

The other two Victorian cases confirmed on Friday were in returned international travellers in hotel quarantine. Professor Sutton said such cases accounted for half of Victoria’s remaining 74 active COVID-19 infections – largely because the state was taking about half of the regular arrivals to Australia.

“They have to go through their quarantine period as international
travellers before they travel on to other states where they are resident,” he said.

“Those individuals, the majority of those, are in a setting where they won’t transmit to others, so I’m not concerned about the number of active cases.”

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Professor Sutton also again urged Victorians not to attend the Black Lives Matter rally planned for Saturday. More than 40,000 people have registered to attend the protest at state parliament, despite Victorian public health regulations banning gatherings of more than 20 people.

“There is a risk that all of the gains that we have made are put at risk by people gathering in large numbers,” he said.

“It takes a single individual who is infectious to potentially transmit to many others in a mass-gathering setting.”

Tweet from @VictorianCHO

He said there were “other ways to protest” and he would like organisers to call off Saturday’s march.

But, if people insisted on attending, they should maintain social distancing, carry hand sanitiser, avoid touching their face – and tell anyone who is unwell to go home.

“I think they probably should wear a mask but I understand there are people there who are wanting to shout, who are wanting to use a megaphone, that’s why this is a risk,” Professor Sutton said.

“There will be a lot of vocal protesting. That’s what protests do – so that adds to my concern about the risk of transmission.”

Victoria Police have said they are unlikely to fine people for breaching coronavirus measures at Saturday’s protest. Professor Sutton said that was “an operational matter for police”.

“I don’t think people should be there. That’s my definitive advice,” he said.

“The potential for other actions is really a matter for police and they’ll enforce it as they see fit.”