COVID-19 has seen several Australian state governments take the extraordinary step of barring entry to other Australians in a bid to stop the spread of the virus.
The closure of the NSW-Victoria border is the first time that's happened in a century.
Prime Minister Scott Morrison has said throughout the pandemic that states should keep their borders open if possible, although softening his stance in light of the recent surge of cases in Victoria.
Mining billionaire Clive Palmer has claimed the WA Government would "destroy the lives of hundreds of thousands of people for decades" if it continued with hard border restrictions.
So where else have internal borders been closed, and has it worked? What lessons might Australia take from experiences elsewhere?
What does the World Health Organization say?
As the pandemic took hold in February, the World Health Organization (WHO) advised against the closure of even international borders, warning that restrictions could "have negative social and economic effects on the affected countries."
"In general, evidence shows that restricting the movement of people and goods during public health emergencies is ineffective in most situations and may divert resources from other interventions," it said.
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But many experts disagree with this assessment.
Dr Norman Swan, host of the ABC's Coronacast podcast, has said "our experience in Australia is different".
"The key thing in this which we've been saying on Coronacast for a long time now is that you go in hard and you go in early, therefore I think it is probably quite reasonable that Queensland shuts its borders to people from Greater Sydney," he said.
"You saw what happened with just a single man arriving in south-west Sydney from Victoria. That's probably the source of most of what's happened in New South Wales over the last couple of weeks."
Acknowledging the reality of the situation, whereby most countries around the world have introduced border restrictions, the WHO this week released guidelines for governments seeking a gradual return to allowing international travel.
China, where the virus was first detected in Wuhan, was the first to impose significant internal border restrictions, cutting off the city and surrounding Hubei province from the rest of the country for two months starting in late January.
Authorities closed all transport into and out of Wuhan on January 23, with its 11 million residents ordered to stay home. All non-essential shops and businesses were forced shut.
This approach has been replicated time and time again throughout the epidemic, with Chinese authorities "ring-fencing" affected areas to contain the spread.