Countries across the Asia-Pacific region are scrambling to slow the spread of the more infectious Delta variant, reimposing restrictions and stay-at-home orders in a jarring reminder — for societies that had just begun to reopen — that the pandemic is far from over.

In Australia, outbreaks of the variant have forced four major cities — Sydney, Brisbane, Perth and Darwin — into strict lockdowns. On Monday, the Malaysian government said nationwide stay-at-home orders would be extended indefinitely. And Hong Kong officials banned flights from Britain, where cases of the Delta variant, which was first identified in India, are rising fast.

In Bangladesh, soldiers are preparing to patrol the streets to enforce stay-at-home orders, with new cases rapidly approaching their early April peak. “The Delta variant of Covid-19 is dominating,” said Robed Amin, a health ministry spokesman, adding that testing suggested the strain was responsible for more than 60 percent of new cases.

The lockdowns and restrictions have deflated hopes across the region, where many countries avoided the worst of the pandemic’s initial spread last year. Now, weary residents are frustrated by what some describe as their countries’ pandemic regression, as other parts of the world edge toward normalcy.