The World Health Organisation is warning nations over their border policies in the pandemic, fearing indefinite closures could severely damage major economies.
There is growing pressure on individual countries to curb their own COVID-19 infections, but some are struggling with the task.
Since March, the world has been at a virtual standstill.
But even as countries including Australia grapple with a second wave of COVID-19 infections, the World Health Organisation says we can't stay shut forever.
The Executive Director of the World Health Organisation's Health Emergencies Program, Dr Michael Ryan, told a press briefing there is a balance between making "progress" and maintaining "pressure" on the virus.
Last week Britain reimposed a quarantine period for travellers returning from Spain - a move that has thrown plans for a European tourism recovery into chaos.
The United States has been hardest-hit in the pandemic, with fatal cases climbing toward 150 thousand people.