More than a year and a half into the pandemic, Australia is facing its worst COVID-19 crisis yet with experts saying a lockdown of its biggest city needs to be ramped up to prevent further deterioration of the nation’s successful record in stamping out the virus.

Though Sydney has been in lockdown for nearly two months now, the curbs are generally looser than those that helped Melbourne beat back the pathogen last year; daily infections have surged from 12 on June 26, when the stay-at-home order was first announced, to records of around 350 this week.

The situation is putting Australia — which had driven locally acquired cases to zero just a few months ago — in the worst of both worlds. Half the population of 26 million people are cooped up again, but the delta variant is still spreading to new cities and regions hundreds of kilometers away, just like it is in reopened economies like the U.S. and U.K.