Dr. Jacobus de Waard, an expert on infectious diseases at the Central University of Venezuela, who has worked and traveled among the Warao for years, said that nothing less than 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.”

The epidemic plaguing the Warao is a crisis within a crisis, a dramatic example of how Venezuela is failing to grapple with a resurgent 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, Venezuela’s economy has crumbled, causing crippling shortages of medicine and diagnostic tests, and compelling many of the country’s best doctors to emigrate.

The government has even stopped distributing free condoms, which can help prevent the spread of H.I.V., activists say. The price for a pack can cost the equivalent of several days’ pay at minimum wage.

The government’s inaction, the activists say, is especially egregious considering that President Maduro — like his predecessor — has cast himself as a champion of the nation’s indigenous people.