Health authorities say communities won’t know for weeks if the mass gatherings of Australians attending Black Lives Matter marches will spark a second wave of the coronavirus.

They’re concerned that if a protester is found to have contracted COVID-19, or have been infectious during the rallies, it will be almost impossible to trace their contacts.

Organisers of gatherings inspired by the protests in the US after George Floyd’s death have copped criticism from the federal government – and in some cases police fines – for ignoring health laws during the pandemic.

They had put in place health measures including hand sanitiser stations, supplied masks, and told participants to remain 1.5 metres apart and self-isolate after the protests.

But as a crowd of tens of thousands swelled in the streets of most Australian capital cities on Saturday and Sunday, and in some regional towns, at times social distancing became almost impossible.

Photos also showed police officers standing shoulder to shoulder and touching protesters during confrontations in New South Wales, with many officers in Sydney pictured not wearing masks.

In Brisbane, where some 30,000 people gathered, police said they were handing out face masks.

“It was a peaceful protest, without any real concerns, and we were happy with how it went,” a Queensland Police spokesperson told the ABC.

Protesters line up in Melbourne to wash their hands at a dedicated Sanitiser Station. Photo: Cait Kelly

But others were not so pleased with the actions of demonstrators, with Liberal politicians attacking protesters and state leaders for being “hypocrites” for putting lives at risk.

On Sunday, senior federal government minister Mathias Cormann dubbed the actions of protesters “selfish”, “self-indulgent” and “reckless”.

“I think about the heartbreak of families who haven’t been able to attend funerals for their loved ones because they were doing the right thing by taking the health advice, my heart just goes out to them,” Mr Cormann said on Sky.

“As they see people going recklessly to these sorts of demonstrations, that must be just awful for them to watch.”

But supporters pointed out they were standing up for the lives of people of colour.

And they felt it was necessary to fight right now for the cause, including highlighting Indigenous deaths in custody, at a time the world was paying attention to the issue – or lose the chance to have an impact.

Victoria’s Deputy Chief Health Officer Dr Annaliese van Diemen speaking on Sunday about the coronavirus and impact of the protests. Photo: AAP

Labor’s spokeswoman for Indigenous Australians Linda Burney said protesters had been “conscious” of the health risks.

Senator Cormann should be listening to the “visceral cries” of people speaking out against inequality, Ms Burney said.

She said Mr Cormann’s home state of Western Australia had some of the highest levels of incarceration of Indigenous people.

“Mathias Cormann should know better than to describe these protests yesterday, this cry from the heart of many thousands of people across the world and in Australia, as self-indulgent and reckless,” Ms Burney said.

Deputy Opposition Leader Richard Marles said he had been “uncomfortable” about mass gatherings amid the pandemic but he would not pass judgment at those who felt compelled to protest.

“I don’t feel like I’m in a position to say to Indigenous Australians, who are protesting against that, that this is a selfish and indulgent act,” he told the ABC’s Insiders program.

Health Minister worries about ‘catastrophic impact’

Federal Health Minister Greg Hunt said he hoped the marches would not lead to a new wave of infections.

“We don’t know whether people will be infected,” Mr Hunt told ABC radio on Sunday.

“But if there is someone who is infectious in the midst of a crowd like that, that can have a catastrophic impact.”

Victorian deputy chief health officer Annaliese van Diemen said the protest in Melbourne had increased the risk for cases and would make contact tracing difficult.

“In terms of potential outbreaks related to the protest, it really will be at least a week and probably closer to two weeks before we have an idea of whether there’s been any transmissions or outbreaks related to that,” Dr van Diemen said.

The impact will take its time to show due to incubation periods, people developing symptoms, getting tested and waiting for results, she said.

But the large number of people they don’t have contact details for does “present a risk, and that is not an insignificant risk”, she said.

Dr van Diemen urged people not to attend gatherings of more than 20 people as per the health directions.

“Our advice has been that people don’t attend gatherings of greater than 20 as per the current directions,” she told reporters.

-with wires