COVID: Delta Variant spreads to Indonesia’s remote, vulnerable islands.

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.

“The spread of Delta has expanded beyond Java," said University of Indonesia epidemiologist Pandu Riono.

“If there’s a major spike, then hospitals, oxygen supplies, intensive-care wards and health services will be overwhelmed." He said this process is already playing out in eastern Borneo, where the variant has been detected. Other places where Covid-19 deaths are rising, government statistics show, include the provinces of Riau, on Sumatra island, and South Sulawesi, northeast of Bali on Sulawesi island.

The center of eastern Borneo’s crisis is bustling Balikpapan, known as “oil city" for its energy reserves. Many of the migrant laborers arriving by ferry and plane from Java in late May, after the Muslim holiday of Eid, tested positive for Covid-19, according to local doctors.

Cases in the city were rising by late June, and soon after in countryside areas like Tanah Grogot, four hours away by car and ferry. The ill converged on Balikpapan, one of the largest cities in the area, for treatment, filling up its hospitals.

Balikpapan resident Yuyun Zainal, 53, said her 63-year-old husband started feeling unwell in early July. At first he refused to see a doctor. “He’s the type of man who doesn’t complain," she said. But alarmed by his fever and shortness of breath, she persuaded him to go to the hospital—but by then, on July 12, the city’s Covid-19 wards were full.

“The doctor explained because of my husband’s condition he needed to be treated in an intensive-care ward," Ms. Zainal said. “But because none were available whatsoever, we had to wait." Within hours, her husband was dead.

Ms. Zainal spoke by phone from a hospital isolation room where she was being treated for Covid-19. Her 24-year-old daughter was also hospitalized after being infected. “I have to get through this," she said. Half of Balikpapan’s Covid-19 deaths since the start of the pandemic came in July.

Family clusters like the Zainals’ have become common during the recent rise in cases. Doctors in Balikpapan say they are exhausted tending to patients who arrive from across the region. “There aren’t any empty beds," said pulmonologist Elies Pitriani. She is one of only eight lung specialists in the city of 700,000, she said. Tanah Grogot has just two.

Cemetery workers are laboring into the night to keep up, Dr. Pitriani said, as the number of recorded Covid-19 deaths climbed to 182 in the fourth week of July, from 45 in the first.

“It’s really extraordinary to us, because Balikpapan isn’t as big a city as many on Java," she said.

In Tanah Grogot, Panglima Sebaya hospital staff are hurriedly doubling the size of the Covid-19 ward, but for now overflow patients are being treated in a tent set up outside.

“Every day there are deaths, because the condition of the patients that come to our hospital are already so severe," said Dr. Nurdiana, the director of the hospital, who goes by one name. Staff members are falling ill with Covid-19 as well, leaving administrators to try to fill gaps with health workers called in from regional clinics.

Dr. Helen said the hospital is struggling with shortages of Covid-19 drugs such as the antiviral remdesivir. She said she is also concerned that local people aren’t strictly following health protocols.

“There are still so many weddings and events," Dr. Helen said. As for vaccinations, she added, the local campaign has proceeded slowly. Even among the elderly, the rate of full vaccination in the town and surrounding area is only about 7%, compared with about 15% nationwide.

Overall, about 8% of Indonesia’s huge population—the world’s fourth-largest—has been fully vaccinated.

Like many developing countries, it has struggled to import enough vaccine, and a large share of the supply has been designated for Jakarta, which has fully vaccinated around a quarter of its 10.5 million people, and the tourist island of Bali, which has vaccinated around a fifth. By contrast, East Kalimantan—the province that is home to both Tanah Grogot and Balikpapan—is at about 8%.

In recent days Indonesia’s daily number of new Covid-19 cases has hovered close to their peak, around 40,000. Deaths are surging, over the past week averaging around 1,700 a day.

Epidemiologists warn that in an archipelago the size of Indonesia—which spans roughly one-eighth the circumference of the earth—spikes will occur at different times in different areas, some of which have limited testing capacity.

In recent weeks, the Delta variant has traveled the country’s length, from northern Sumatra, near Malaysia, to far-eastern Papua province, on the island of New Guinea.

“The other islands will face their own curves," said Dicky Budiman, an Indonesian epidemiologist at Griffith University in Australia. “I can see now that Sumatra, [Borneo] and Papua at least, they start their crisis now."

This story has been published from a wire agency feed without modifications to the text - Wall Street Journal