No matter how laudable the cause of Tuesday's Black Lives Matter planned protest in Sydney, it was ridiculous to even contemplate having a gathering which had anticipated 500 or even 4000 people – even if wearing masks – giving voice (and potentially virus) to their shared concerns for a prolonged period of time.

While the organisers had pledged to divide into legal groups of no more than 20, how feasible was that among such a large assembly? As it turned out, the rally leader was arrested and the protesters – much smaller in number than had been feared – dispersed.

But it shouldn't have come to that. What irony that a protest about the need to save lives could be responsible for the loss of lives. It’s disturbing that after all these months of struggle to contain COVID infections, the organisers were defying a court order not to proceed. As we have seen in Melbourne, a single carrier can set off a tidal wave of infections.

Prolonged exposure to COVID carriers results in "clusters" of infection as we have seen in meat-packing plants, nursing homes, cramped housing estates and, increasingly notable, hospital settings.

More than 700 Australian health professionals caring for COVID patients have been infected. In the Italian crisis more than 100 previously healthy and often young doctors died as they were constantly exposed to huge numbers of infected individuals over many weeks.

Now, you might get infected making you way around a crowed supermarket. You might pick up COVID from a solid surface or meet it in air exhaled by a fellow shopper, but the risk is low. To avoid the greater risks, we have to extend our thinking to social brevity.

Religious services, choirs, funerals, parties, hotels where drinking while standing in groups is allowed, public transport and the normal daily routines in nursing homes all create dangerous opportunities for infection.

The data also highlight how important are opportunities to work at home. We need to pay special attention to the working conditions associated with "essential services". We have had clusters of infection on construction sites and in factories. Industry experts should be working with government health authorities to devise the best possible protective gear and arrangements for workers in such industries.

The recent outbreak of infections in Victoria clearly illustrates how quickly we can see a reassuringly low rate of new infections explode to produce so many new infections that our best efforts at contact tracing are unable to arrest the exponential increase in cases.

In NSW we are understandably nervous that our currently manageable numbers of new infections could suddenly accelerate.

While vaccine news features much optimism, the data is very preliminary and we are learning from numerous studies that natural infection may not be associated with any long-term immunity.

Too often we hear that COVID infections are only a problem for "oldies". Yet globally they are causing more and more serious clinical consequences for young people (very noticeable in Victoria at the moment), often resulting in chronic illness.

It was of some comfort that the Black Lives Matter protesters ploedged to wear masks, but that would give them no guarantee. Numerous studies have been performed trying to quantify the value of mask wearing by the general population as a strategy for defeating COVID; the results are mixed. The controversies are well presented on the NSW Department of Health’s COVID website.

The wearing of masks by all citizens, as is currently required of Victorians, needs to be put into an evidence-based perspective. There is no doubt about the effectiveness of masks in reducing the likelihood that an infected individual will infect another.

Of course, individuals with respiratory symptoms should wear a mask as they seek testing and then self-isolate until the results are in. No-one with symptoms should be at large in the community and thinking that a mask will guarantee they are harmless.

The World Health Organisation and America’s Centres for Disease Control and Prevention recommend the importance of mask wearing by all in situations such as Victoria’s. Certainly the same is true for the likes of Florida and Texas where 25 per cent of those tested are infected, but mask wearing will not provide the panacea that will terminate the COVID epidemic.

Stay-at-home orders will slow the infection rate but our need to "live" with this virus and restore our economy requires us to adapt our normal social interaction to the long-term epidemiological reality we face. That adaptation must address the need for "social brevity" for the foreseeable future.

John Dwyer is an immunologist and Emeritus Professor of Medicine at the University of NSW.