Australia

SYDNEY, Australia — One case. One young security guard at a quarantine hotel who tested positive for the coronavirus and experienced minor symptoms.

That was all it took for Perth, Australia’s fourth-largest city, to snap into a complete lockdown on Sunday. One case and now two million people are staying home for at least the next five days. One case and now the top state leader, Mark McGowan, who is facing an election next month, is calling on his constituents to sacrifice for each other and the nation.

With coronavirus infections rising and a contagious new variant threatening to accelerate the pandemic, France has implemented a stringent 6 p.m.-to-6 a.m. curfew. Citizens nationwide are sequestered indoors, and businesses must close down.

In Quebec, Canadian officials imposed a similar restriction earlier this month, running from 8 p.m. to 5 a.m. It has frayed nerves: Notably, a woman who was walking her boyfriend on a leash at 9 p.m. has argued that this was permitted during the curfew, surely one of the pandemic’s most unexpected moments.