After the other villagers had drifted away to do chores, Rafael Pequeño finally found himself alone with the headman and opened the hardcover notebook on his lap. The men were sitting in a palm-thatched hut perched on stilts on the edge of a branch of the Orinoco River.

It had been two years since Mr. Pequeño, a nurse, had visited this poor indigenous village in the Orinoco Delta region of eastern Venezuela. His notebook contained a registry of patients who had been in an H.I.V. treatment program that, like the rest of the nation’s public health system, had crumbled.

Mr. Pequeño took a roll call of the infected.

«Armando Beria,» he said.

«Still here,» replied the headman, Ramón Quintín.

«Ebelio Quinino,» the nurse continued.

«Still here.»

«Mario Navarro.»

«Dead.»

«Wilmer Medina.»

«Dead.»

Of the 15 villagers who had been part of the treatment program, five had died of AIDS, the disease caused by H.I.V. In all, more than 40 residents of this village had died of AIDS or AIDS-like symptoms in the past several years — in a settlement of only about 200.

«I’m very worried,» Mr. Pequeño said. «It’s wiping out this community.»

In recent years, amid profound shortages of medicine coupled with widespread ignorance, H.I.V. has spread rapidly throughout the Orinoco Delta and is believed to have killed hundreds of the Warao indigenous people who live in settlements like Jobure de Guayo.

Already, deaths and the flight of survivors have gutted at least one village, but the government has ignored the issue, medical specialists and Warao community leaders say.

Dr. Jacobus de Waard, an expert on infectious diseases at the Central University of Venezuela, who has worked among the Warao for years, said the future of the ancient culture was at stake. «If there’s no intervention, it’s going to affect the existence of the Warao,» he warned. «A part of the population is going to disappear.»

Venezuela is failing to grapple with an AIDS emergency even as the annual numbers of new H.I.V. infections and AIDS-related deaths around the world continue to decline.

Under President Hugo Chávez, Venezuela’s H.I.V./AIDS prevention and treatment program was world class, and the country seemed to have the disease under control. But during the presidency of Nicolás Maduro, which began in 2013, the economy has crumbled, causing crippling shortages of medicine and diagnostic tests, and compelling many of the best doctors to emigrate.

The government has stopped distributing free condoms, activists say. The Maduro administration did not respond to requests for interviews with officials of the national H.I.V. prevention program, the health ministry and the ministry of indigenous affairs.

Among the most disadvantaged Venezuelans are the Warao, said Jhonatan Rodríguez, president of StopVIH, a Venezuelan activist group. «It’s a population that has been totally neglected.»

The Warao have lived for centuries in the delta region. Numbering about 30,000, they live in hundreds of remote impoverished settlements.

Armando Beria, 25, a resident of Jobure de Guayo, who was on Mr. Pequeño’s patient list, said he first heard about AIDS when a doctor visited the settlement in 2013 and tested people for the virus. «I did the examination and he said, ‘You have it, too,’ » he recalled.

He believes he may have contracted it through having sex with other men when he was younger — a common practice among young Warao.

Researchers believe that men having sex with men was part of the early dissemination of H.I.V., but the virus is now rampant in the broader population, and heterosexual sex and breast milk now appear to be other forms of transmission.

No family in Jobure de Guayo had been hit as hard by the epidemic as the headman’s extended clan, which had lost at least 12 people to AIDS or AIDS-like symptoms in the last two years. «In the past, if you were sick, they did everything possible to hospitalize you. Now, no,» he said.

«My people are dying.»

Some in his family say they have fallen victim to a curse inflicted on them by a former village resident whom others accuse of being a hoarotu, a darker kind of shaman.

Mikaela Perez, 33, a granddaughter of Mr. Quintín, said the villager put a hex on her father, whose death from AIDS-like symptoms was followed by a rash of others in the family.

«A family that’s coming to an end,» she said. «Before we all lived together very happily. But now it’s coming to an end.»

Doctors flee as a health care system crumbles.