Johnny Chen was a hard-driving American businessman based in Shanghai, used to making things happen. So he was dispirited, even angry, when, after a visit to Hong Kong, he became fatigued and feverish and wound up in a hospital bed here.

Chen checked into Hanoi French Hospital, the city's only private hospital, in late February with a 104-degree fever, a sandpaper cough and muscle aches that would alarm an Italian parasitologist, Carlo Urbani, who would alert the world to a strange, new respiratory disease.

By the time Chen died on March 13, four days after his 49th birthday, it was clear to a group of health care experts that the businessman was the victim of a new disease. A day earlier, the World Health Organization had put out a global alert.

But on April 28, just six weeks after Chen died, Vietnam's government was able to declare the country the first in the world to contain severe acute respiratory syndrome, or SARS.

It would appear unlikely that a poor communist country could become the first to tame a mysterious, contagious disease. But Vietnam's handling of SARS is a tale of decisiveness, cooperation and luck, in which early detection and strong infection-control measures under the guidance of international experts gave Vietnam an edge.

In Hong Kong, Chen had stayed at the Metropole Hotel, where he is believed to have been infected by a Chinese doctor who picked up the virus treating sick people in southern China.

Chen, a merchandise manager for a New York garment manufacturer, had come to Vietnam to visit a factory that produced jeans and shirts for his company. He was hospitalized on Feb. 26 with body aches, and he coughed and coughed.

Olivier Cattin, a hospital doctor, thought that perhaps Chen had picked up avian flu in Hong Kong.

Two days later, Vu Koang Thu, a doctor at the hospital, called the World Health Organization and reached Urbani, WHO's communicable diseases expert in Vietnam. Urbani looked at X-rays of Chen's chest and advised the hospital to take blood samples and throat swabs, which were sent to WHO collaborating labs in Tokyo and the Centers for Disease Control and Prevention in Atlanta, and the National Institute for Hygiene and Epidemiology in Hanoi.

One night, wracked by pain, he cried, awakening a patient two doors away. The next day, a Saturday, Chen was told that he needed his blood drawn, but he insisted that "only a French doctor prick him," Thu said. A French doctor assured him that would be the case. Chen closed his eyes, and a Vietnamese nurse plunged the needle into his arm. He never knew.

By that Sunday, Chen could not breathe. His lung X-rays were completely white, a sign the lungs were inflamed, infected or filled with fluid. He was moved to an intensive care unit and hooked to a ventilator, sedated so that he would not fight the machine.

On March 4, his wife arrived from Hong Kong. On March 5, an international medical evacuation company flew him to Hong Kong. He died there seven days later in Princess Margaret Hospital.

Urbani and Hitoshi Oshitani, a WHO communicable disease expert from Manila, began to suspect that there might be a connection between the illness in Hanoi and an atypical pneumonia epidemic in Guangdong province in southern China, news of which was trickling out.

On March 7, alarmed by Urbani's daily reports of mounting infections among health care workers, WHO activated its Global Outbreak Alert and Response Network, a grouping of public health specialists who stand ready to respond to outbreaks around the world.

Urbani and Pascale Brudon, WHO's Vietnam representative, asked for a meeting with Vietnamese health officials. Urbani and Brudon worked the phones furiously, calling various officials.

The Vietnamese officials agreed to meet March 9 at the Health Ministry. At first, they were not convinced of the problem's severity because their lab tests showed that the virus was influenza B, and not thought to be linked to the outbreak in China. Besides, the infections were limited to one hospital, WHO officials recalled. But Urbani explained that the disease was very contagious and dangerous.

But by the end of the two-hour meeting, the vice minister of health, Nguyen Van Thuong, had agreed to allow WHO to summon an international team of experts. He also promised to organize a task force at the ministry that would review the situation daily.

It was, Brudon said, a "turning point."

Vietnam's response contrasted with that of China, which for weeks tried to conceal the extent of its outbreak. But a health official in Vietnam, Le Thi Thu Ha, said her country made a simple calculation: "We needed that technical assistance," she said.

On March 12, two WHO team experts visited the Hanoi French Hospital to help the doctors and nurses there halt the disease.

In the parking lot, 15 members of the health care staff, in surgical masks, advanced on the pair, eager for answers about the disease that was making their colleagues deathly ill.

"They kept converging upon us," said Tim Uyeki, an epidemiologist with the CDC who had flown in from Atlanta. The two experts kept backing away, hospital officials said.

"It was surreal," a doctor said.

That week, the Health Ministry set up a task force. Days later, a dozen epidemiologists and pathologists had arrived from Britain, the United States, Sweden, Germany, France and Australia.

"You need a heap of people to chase the cases, read the notes, find out what's going on, respond to new things, help set up new measures," said Aileen Plant, the WHO coordinator for the SARS expert team. "Are you following the contacts? Are you putting infection control in place? What are you going to do with a dead body? Can people breast-feed? All of these sorts of things, you've got to think about really fast."

Meanwhile, Urbani was scheduled to attend a meeting in Thailand. Before he left, he called Brudon from the airport, saying he felt feverish. She told him it was probably just fatigue -- he had been working 16-hour days for 10 days. He flew to Bangkok. He was admitted to a hospital there, and died on March 29.

Urbani was not the only medical worker to be infected. On the day that Chen, the American, left the hospital, four doctors and nurses were admitted as patients. The next day, seven more followed. By Tuesday, March 11, two dozen health care workers were in the hospital -- one-quarter of the health care staff.

The situation was tense, staff members recalled. The hospital caterer refused to provide food. People rode by the three-story building on motorbikes with their shirts held over their mouths. When doctors crossed the street to buy a pack of cigarettes, shopkeepers would turn them away.

"It was very, very stressful," said Nguyen Nang Tan, 36, a doctor who also was admitted to the hospital. "I thought that everyone could get sick and die."

On March 15, Nguyen Thi Luong, the nurse who had tended to Chen, died.

On March 19, Jean Paul Derosier, the anesthetist who had put Chen on a ventilator, died.

On March 24, gynecologist Nguyen The Phuong and nurse Nguyen Thi Uyen died.

On April 12, Nguyen Huu Boi, an orthopedist, died.

Most of the Vietnamese doctors and nurses who remained healthy wound up sleeping at the hospital, because of fears that they could spread the infection. Effectively, they isolated the virus at its most infectious point, health experts said.

"So you ended up with the situation where they probably infected each other much more than would have happened in some communities, where they might have been at home and infecting their families -- not all of them, but quite a lot, enough of them, to change the chances of infection" to the broader community, said Plant.

Hanoi French Hospital stopped admitting new patients on March 11. But it kept its own ill staff, finally shutting its doors on April 12, the date of the last patient's death. The hospital has been decontaminated and is slated to reopen in June.

Vietnam began an extensive effort to find everyone who had contact with a SARS patient, a process health workers call "contact tracing." Most cases involved only health care workers and their immediate family. In one instance, however, a man whose daughter underwent surgery at Hanoi French Hospital became infected. He lived in Ninh Binh province, 44 miles from Hanoi. Vietnamese health care workers located 128 people who had had contact with him. "We asked them to stay at home," said Ha, the health official. "Our health care staff came to visit them every day, for 14 days."

The Vietnamese task force eventually designated Bach Mai's Medical Institute for Tropical Diseases as the SARS facility. WHO and CDC officials were alarmed when they saw that Bach Mai was accepting SARS patients even before the facility was properly equipped. It lacked N-95 respirator masks to protect against SARS. As is the custom in Vietnam, family members continued to flock to patients' rooms to feed, bathe and help care for their ill relatives.

But WHO and the CDC quickly donated masks, gowns and other equipment. Japan contributed similar supplies and two ventilators. Doctors Without Borders, an international group of volunteer medical professionals, sent a team to help. Workers were trained in infection control techniques.

Doctors at Bach Mai said the hospital's lack of air conditioning forced them to throw open doors and windows, which they said helped contain the virus by dispersing any particles that might otherwise adhere to surfaces and people.

More important, WHO officials said, the patients admitted to Bach Mai by and large were not as sick as those at Hanoi French. And unlike other countries, in which more than one patient passed the disease on to others, all of Vietnam's 63 cases, including 36 health care workers, can be traced to Chen.

"There's a bit of luck here," Ha said.

Vu Khac Khoan, 76, and Nguyen Duc Khiem, 67, Vietnam's final two SARS patients, were released Friday from Bach Mai Hospital, which became the main SARS facility. At a memorial service in Hanoi, the World Health Organization's Tran Cong Dai bows before a photo of Carlo Urbani, a physician who alerted the world to SARS. Vu Koang Thu, a doctor at Hanoi French Hospital, in the room that was occupied by Johnny Chen, an American businessman who died of SARS.Vu Khac Khoan, who recovered from SARS while at Bach Mai Hospital, claps in appreciation of the doctors and nurses who cared for him. He was released from the hospital on Friday.