For 18 months, a town in a remote, heavily forested part of eastern Borneo island had avoided the worst of Indonesia’s Covid-19 pandemic.

Then, in early July, doctors in Tanah Grogot started seeing what they had long feared: a rush of coughing and feverish patients on the threadbare, medicine-short hospital facilities. Deaths have ticked steadily upward.

Only a small supply of vaccine has reached this town of 75,000 set among palm-oil and rubber plantations. The only hospital, Panglima Sebaya, has just six ventilators—all in use by late July.

“There aren’t enough beds, medicine is difficult to come by,” said Widy Helen, a physician who treats patients there. Of the area’s 162 Covid-19 deaths since the start of the pandemic, more than a third came in July.

Indonesia, an archipelago that stretches more than 3,000 miles along the equator, is suffering one of the world’s worst Covid-19 surges. Driven by the highly infectious Delta variant, the outbreak has overwhelmed hospitals. Cases and deaths—recently running at about 1,700 a day—have been concentrated on the main island of Java, home to the teeming capital city of Jakarta and more than half the country’s 270 million people. But medical experts worry that Indonesia is entering a dangerous new stage.