Australia will have to show a negative COVID-19 test before they can get on their plane, the prime minister said on Friday, as the city of Brisbane went into lockdown after the discovery of a case of a virulent new coronavirus variant.The more than 2 million residents of Brisbane, Australia's third-largest city, will be barred from leaving their homes for anything but essential business for three days from Friday evening after a worker at a quarantine hotel tested positive for the new variant, which was first detected in Britain.Also read Virus spread slows but two states still a worryAustralia has found several cases of the variant but this was the first one to appear outside the quarantine system.