More than 300,000 citizens and permanent residents have returned to Australia since March 13 when the scale of the unfolding crisis became clear and the Government ramped up its travel warning.

In the two months since, travel has come to a halt and leaving the country has been banned.

But for Chris and Mietta, the option to rush home was considered and swiftly rejected.

"We actually heard the news from Mietta's mum that the Prime Minister told … every traveller to come home," Chris said.

"It didn't really fit with what we wanted to do."

Chris is a mechanical plumber and Mietta is a registered nurse, but they packed it up in March 2019 and set off for a three-year trip through north, Central and South America.

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They had made it as far as Mexico when news of the pandemic broke.

"It would have cost us thousands of dollars and we would have just been stuck in the same spot but at home and not been able to do anything anyway," Mietta said.

"And because we have a long travel plan and weren't just gone for a couple of weeks we knew we could afford to stay."

The couple is part of the van life movement, living in their self-sufficient Ford Transit.

But it's not all smooth travelling.

They have heard stories of foreigners being chased out of towns by angry locals with machetes, or people calling the police to get them to move on.

Then there is the issue of their visas and the permit for their van — both of which expire next month.

"If the Mexican Government doesn't extend them for the crisis period then we're actually going to have to make a run to a border so we can hand in our visas and our import permit for our car and then renew them, and then come back to the ranch," Chris said.

"[We're] hoping by the end of June something has changed and we don't have to do that."

'Return now or prepare for a long stay'

The Federal Government doesn't track where Australians are, but before coronavirus spread, it estimated that at any one time more than 1 million were abroad.

Many are likely to be expats with established homes and careers overseas.

For the remaining travellers like Chris and Mietta, the Department of Foreign Affairs and Trade (DFAT) is urging them to come home now or plan for a long stay away.

And it warns it may not be possible for them to fly back at a time they choose.

"With the global shutdown of borders and transit hubs, it won't be possible for every Australian traveller to get home until the travel restrictions are lifted," DFAT says.

"If you can't leave or prefer to stay where you are, make plans to remain for an extended period."

Sweet.

In Mexico, the Government has declared a national emergency and all non-essential activities have been suspended. Most states have curfews or restrictions on movements.

There have been more than 33,000 recorded cases of coronavirus in the country and more than 3,300 deaths, according to the tally by Johns Hopkins University.

Mexico has limited testing compared to many other countries, leading experts to fear the number of infections is much higher. And they warn the worst could be yet to come.

"We have to prepare ourselves for the hardest, ugliest part," Dr Mauricio Rodríguez, of Mexico's National Autonomous University, told Associated Press.

Chris and Mietta hope to stay in the Americas until their planned return in December 2021, and until then they don't want to be a burden on the local health system.

"Mexico, we definitely understand, would not cope very well with a flooded health system," Mietta said.

"If we were really unfortunate enough to catch something or get sick, we definitely wouldn't be using the healthcare system.

"We wouldn't be going to the doctors or hospitals, we would just have to isolate."

And, Chris adds: "Our health insurance ran out in March anyway, and we can't reissue it."