The number of coronavirus cases in Australia reached 208 on Friday evening, including three deaths. In at least 14 of those cases, the source of the infection has not been determined.

Professor Nigel McMillan, director of the infectious diseases program at Griffith University, said the federal government should activate extreme social-isolation measures when the number of COVID-19 cases hits 250 nationally. But he believes NSW should act sooner and immediately activate social isolation measures, given the number of human-to-human transmission cases there. "Italy went from 79 to 2000 cases in seven days so everyone needs to plan for this right now," Professor McMillan said. "Because when it comes, it will come quickly." Italian soldiers process passengers leaving from Milano Centrale train station. Credit:Getty

In NSW, the virus appears to be spreading through the community at a low pace, Professor McMillan said. Victoria had its first case of a community-transmitted infection, which could not be traced, on Friday. What extreme social distancing looks like The Italian government locked down the country this week, closing almost all shops and banning any travel without a police check. A military checkpoint at Milan's central station. Credit:Bloomberg Closing schools could cut virus spread by up to 50 per cent, according to the federal government's influenza pandemic plan. But that would cause extreme disruption as parents would be forced to take time off work.

The number of people allowed on public transport would likely to be severely limited. "In a pandemic situation, you'd cut the number of people down to one person per seat," said Associate Professor Adam Kamradt-Scott, who helped author the federal government's influenza pandemic strategy. People standing would be required to give each other at least one metre of space. That could lead to a huge capacity crunch. An E-class tram in Melbourne is designed to hold 210 people, for example. But it has only 64 seats. However, work hours could be staggered to reduce the number of people needing to use public transport at the same time.

Shutting businesses is less effective and even more disruptive, according to Professor Kamradt-Scott. At least one-third of the nation's offices would need to close to help bring an outbreak under control, he said. Perhaps the cheapest and best measure in the plan is to ask businesses to have their employees work from home – studies have shown that this can reduce the infection risk by 20 to 30 per cent, the professor said. Eventually so many people would fall sick the government would probably stop testing for the virus, he said. "The virus is very mild for most people. There is not much point."

Professor George Milne's research team at the University of Western Australia has built a detailed mathematical simulation of how COVID-19 would flow through an Australian city. The coronavirus pandemic model tracks every single person in a version of Newcastle, simulating how they go about their daily activities. His data, which he hopes to publish this weekend, shows the most effective methods are self-isolation for people feeling unwell, combined with encouraging people to avoid close gatherings. "That’s going to the pub, going on public transport, going out for a coffee," he said. "Our model estimates that with no interventions two-thirds of the population will become infected, though a significant proportion of those would not show signs of being ill." That number could be substantially reduced using social-distancing measures.

'Social-distancing burnout' However, both Professor Kamradt-Scott and Professor Milne do not believe social-isolation measures should be activated hastily. Professor Kamradt-Scott said there was no guarantee sustained community transmission would happen in Australia. "There is no guarantee at the moment this is inevitable. It's important people remain calm, they continue to go about their daily life," he said. Professor Milne believes Australia has not yet reached the point where extreme measures should be activated.