Prime Minister Scott Morrison has advised against all non-essential mass gatherings of more than 500 people as of Monday to stop the spread of coronavirus .

"Now that of course doesn't include schools or university lectures, does not mean people getting on public transport or coming to airports or things of that nature," he said in a press conference today.

"These events that we are seeking to advise against and restrict ease for non-essential, organised gatherings of persons of 500 or more."

Scott Morrison today. (Dominic Lorrimer)

Chief Medical Officer Brendan Murphy said the decision to advise against mass gatherings was "a precautionary measure".

"We have seen increases in numbers every day, and we will feel there will be such a point over coming weeks that it is time to take precautionary advanced measures to limit those large events where the incidents of transmission can be supported," Mr Murphy said.

"We are not suggesting people should interrupt their normal daily work. It's just avoiding those particular circumstances where transmission can be accelerated. This is the unanimous advice of all of the Chief Health Officers."

Mr Morrison also urged Australians to reconsider all international travel.

How coronavirus cases have spread around the world since January. (Graphic: Tara Blancato)

Empty baggage check-in lines inside in International terminal at Tullamarine Airport, Melbourne. (AAP)

"We have also decided today through the Department of Foreign Affairs and Trade that we now advise all Australians to reconsider your need to travel overseas at this time, regardless of your destination, age or health, travel is not essential, consider carefully whether now is the right time," he said.

"So we are effectively putting in place what is called a Level 3 travel advice for travel of Australians overseas."

When asked about the closure of schools, NSW Premier Gladys Berejiklian said advice is likely to change as the weeks go on.

"It is safe to go to school and when it is not, we will shut down that particular school and work with the school community to reopen at the appropriate time," she said.

"If we feel that anybody's health is compromised, if we feel there is a great risk to the community we will take those decisions.

"What we decide today may be different from next week and the week after. We have to make very clear that it is an evolving situation but at this stage there is no reason for us to change the existing policy we have been adopting in NSW, but again, that is really advice we will take from the health experts. To this point we will continue to maintain that policy."

Nine's Political Editor Chris Uhlmann has said the forming of a national cabinet is unprecedented.

Coronavirus fatality rates (Graphic: Tara Blancato)

Tips for self-isolation as the coronavirus spreads. (Nine)

"Make no mistake now, Australia is on a war footing," he said.

"We are now travelling in waters that we have not chartered since 1919 when we were hit which the Spanish flu. Life as we all know it is about to change remarkably.

"That National Cabinet which includes the Prime Minister, the State premiers and the Chief Minister is a first in Australian history."

Uhlmann said businesses such as airlines will be hit hard by the travel ban, and the fact Australia is heading in to flu season will be another challenge.

"This will be a year that none of us will ever forget."