Loading Mr Lipsitch said many who contract the virus would not have severe symptoms, with some being asymptomatic. He said the disease might not be contained and could become a new seasonal disease similar to the flu. "We don't know what the vulnerability of the world's population is … it might be a quarter of the world's population but it might be 70 per cent," Dr Sutton told radio station 3AW. Dr Sutton said shutting down Australia's borders in the case of a pandemic – where rapid rates of human-to-human infection occur globally – would be too difficult to execute and would potentially need to extend for years if the virus was not eradicated. His comments came as a seventh person was confirmed with coronavirus in Victoria.

A third Victorian passenger from the Diamond Princess cruise ship docked in Yokohama, Japan, had tested positive for the virus, Dr Sutton said on Tuesday. The three have been repatriated to Victoria and are recovering in isolation. Formula One's governing body has postponed the Chinese Grand Prix, scheduled for mid-April, because of the outbreak, which has widened to South Korea, Italy and Iran in recent days. Dr Sutton said health authorities were monitoring whether the race at Albert Park should go ahead and said it would take an "extraordinary" rise in cases for it to be to cancelled. The grand prix generates about $40 million in economic activity for Victoria, according to the state government. "I think we keep [the grand prix] under review, but these events are planned for months and months in advance," Dr Sutton said.

"It would take some extraordinary activity of coronavirus in Australia to cancel something like that at this stage." Dr Sutton said the economic benefit of the grand prix needed to be considered and said halting the event might not be the appropriate way to counter a localised outbreak in Victoria. Dr Sutton said he and his interstate colleagues would continue to provide federal and state cabinets with advice on whether events such as the grand prix posed a public health risk. Is it a pandemic? While the World Health Organisation has already declared COVID-19 a global health emergency, whether or not it is a "pandemic" is another matter. According to the WHO, a pandemic, colloquially, refers to "a new pathogen that spreads easily from person to person across the globe”. But since the world’s last pandemic - swine flu in 2009 - the organisation has moved to a different “phasing system” to measure such outbreaks, meaning pandemic is no longer a designation triggering a formal response. The WHO may use the word, spokesman Tarik Jasarevic says, but it has already put the world on alert in declaring an emergency last month. As for whether the word "pandemic" fits the current coronavirus outbreak, WHO director-general Tedros Adhanom Ghebreyesus says the window to contain the virus has not yet closed though further investment from countries is still needed to stop it in its tracks. Grand prix organisers said they were considering the risks posed by the virus but insisted planning for the race was going ahead as normal.

"Absolutely [the risks] are being considered," said Australian Grand Prix Corporation chief executive Andrew Westacott, "[but events] continue to go ahead as they should, otherwise we're going to close down our city and stop interaction and stay behind closed doors." Mr Westacott said there were strong health protocols in place and organisers were collaborating with authorities to ensure health and hygiene practices were at the level required. Most Formula One teams are based in western Europe. Teams have spent weeks testing their cars in Barcelona. Loading Replay Replay video Play video Play video Two teams, Ferrari and AlphaTauri, are based in Italy near the town of Bologna, less than 200 kilometres from Milan and Venice, where quarantine restrictions have been enforced following a spike in coronavirus cases.

No special health testing of racing team crews has been organised. They will be screened at the airport in the same way as other travellers entering the country. Loading Team crews, which include dozens of members including engineers and race tacticians, are altering their travel routes to Melbourne to avoid traversing Asia, according to Mr Westacott. Coronavirus is a respiratory illness. It appears to start with a fever, a cough or shortness of breath and can lead to pneumonia and more serious complications including organ failure. Anyone can fall ill but, as with most respiratory illnesses, it seems those most at risk of deadly complications are the elderly and people with underlying conditions.