Scientists have warned ‘zero Covid’ is near impossible with the Delta strain, which is many times more infectious than the original virus that emerged in China.

In Australia, where more than 25 million are under lockdown, the Premier of Queensland has been forced to request troops to be sent to the border with New South Wales to help enforce tighter restrictions and stop the highly infectious Delta variant from passing through.

Annastacia Palaszczuk has repeatedly expressed fears about the rising number of cases in NSW and how that could spill over to Queensland, while chief health officer Jeannette Young said one Delta Covid-19 case in the state could spark another lockdown.