JANDI MERIAH, Indonesia -- Dowes Ginting, the most wanted man on Sumatra island, lay dying. He had abandoned the hospital where he had seen his relatives succumb one after another, and he had fled deep into the mountains, trying to outrun the black magic he feared had marked him next. For four nights, witnesses recalled, a witch doctor hovered over him in a small clapboard home, resisting the evil spell.

Mr. Ginting had watched disease burn through his family over the previous two weeks, killing six and sickening two others, including himself. International health experts grew increasingly concerned when laboratory tests confirmed they were sickened by bird flu, the largest cluster of the disease ever recorded. But the wiry 32-year-old feared medical treatment more than he did the flu. And so he ran.

In the end, the outbreak in May did not presage the start of a worldwide epidemic. But the enormous difficulties that Indonesian and international disease specialists confronted in investigating the outbreak and protecting against its spread raised fundamental questions about whether bird flu could be contained if it mutated into a form more easily spread among people.

"If this were a strain with sustainable transmission from human to human, I can't imagine how many people would have died, how many lives would have been lost," said Surya Dharma, chief of communicable disease control in North Sumatra province.

Officials from the World Health Organization, drawing on sophisticated computer modeling of a theoretical bird flu outbreak in Southeast Asia, have suggested that a pandemic could be thwarted through a rapid containment effort in the affected area, including the right mix of drugs, quarantines and other social controls. To succeed, the antiviral drug Tamiflu would have to be distributed to 90 percent of the targeted population, roughly defined as those within at least a three-mile radius of each case. The drug would have to be administered within 21 days from the "timely detection" of the initial case of an epidemic strain. Residents would have to stay home, limit contact with others and take the medicine as prescribed.

In the case of the North Sumatra cluster, almost none of this happened, according to extensive interviews with health officers, family members and villagers in several areas of the province. The underlying problem was that most family members and many villagers were convinced that black magic, not flu, was to blame.

"How can you ever get people to cooperate if they don't even believe you?" Dharma said.

Scientists are still working to determine how bird flu is transmitted to and between humans. More than 200 people worldwide have contracted the deadly H5N1 strain of the virus since 2004. Most of the cases have resulted from direct or close contact with infected live or uncooked poultry, or with surfaces contaminated by infected birds.

Health investigators have concluded that the eight-person cluster in Sumatra began with Dowes Ginting's older sister, who fell ill in late April. They suspect she was infected with bird flu from live chickens sold in a market where she peddled oranges, limes and chili peppers, or from contaminated poultry droppings in manure used in her garden. She died and was buried before any samples were taken to confirm bird flu.

Several days after she became sick, the extended family gathered in the village of Kubu Sembilang for a feast of roast pig and chicken curry to celebrate the annual harvest festival. That night, many of the relatives slept in the same small room with the sister, who had developed a serious cough. By the time she died, a sister, a brother, two sons, a niece and a nephew had become ill. Flu specialists said the final victim, Dowes Ginting, likely caught the virus from his infected son.

Health experts have concluded this was the first time the bird flu virus was passed from one person to another and then on to a third person.

"None of us thought it was bird flu. We thought it was black magic," said Anestia Tarigan, the wife of the youngest Ginting brother, Jones, the only victim to survive. "Everyone in the family was getting sick and no one else was. Someone had put a spell on our family. Black magic is very common in our place."

At the hospital in the provincial capital, Medan, members of the Ginting family were proving uncooperative. More than a dozen relatives had come down from the mountains. They had been sent there by a smaller clinic, and they remained unconvinced that bird flu was what ailed them.

They initially balked at taking Tamiflu or receiving injections of antibiotics, doctors said.

Jones, the youngest sibling, ran away.

"I was losing hope. I thought I was going to die," he said in a raspy voice. He had once been a young tough, but his arms and legs, covered with elaborate tattoos of red and green, had grown scrawny after more than two months of battling the disease.

He returned after villagers told him that the police were looking for him.

But he continued to resist treatment, initially refusing to take medicine or give blood samples. Finally, doctors reached a deal with family members, allowing them to invite a witch doctor to the hospital in return for blood specimens from Jones Ginting.

Agenda Purba, a witch doctor from Jandi Meriah, traveled six hours by van to the hospital. It was midnight by the time he started the ceremony in the special bird flu ward, he said.

Purba chanted over 21 betel nut leaves, each about the size of his calloused palm and filled with blossoms, a pasty white lime, brown chunks of an astringent and bits of an orange-colored nut. He prayed for the young man's recovery. Then Purba chewed the first of the leaves and softly spit onto Jones' forehead. The witch doctor repeated the process until he had finished the leaves, slathering the torso, arms, legs, hands and feet, making sure to cover all the joints.

When Dowes Ginting developed a fever and began coughing, he fled in search of a witch doctor, just as his younger brother had done a week before. Another medicine man in Jandi Meriah, Suherman Bangun, began the incantations and betel-nut spit treatment. After three days, Indonesian and international health investigators tracked the sick man to the village and urged his family to take him to a hospital. The relatives demurred: They said he required two more days of traditional treatment.

That night, Dowes took an abrupt turn for the worse and Shortly before dawn, he died.