In the southern Chinese province of Guangdong, the health department received a "top secret" document from a government health committee on Jan. 27 that contained disturbing information about a new pneumonia-like illness spreading in the region, according to medical specialists and provincial health officials.

Instead of declaring a health emergency, they said, the health department did nothing.

For three days, the document sat unopened because there was no one with sufficient security clearance to open it, according to health department sources with direct knowledge of the case. When authorized officials finally read the document, a bulletin was sent to hospitals across the province. But few health care workers were alerted because most were on vacation for the Chinese New Year, they recalled.

In the meantime, the illness, known as severe acute respiratory syndrome, or SARS, was infecting hundreds of patients, moving throughout China and spreading to Hong Kong and 16 other countries. Chinese officials waited more than three months to acknowledge the extent of the illness, which has now affected at least 2,223 people worldwide and killed 78.

Only today did the Chinese government agree to allow World Health Organization researchers to travel to Guangdong and investigate the illness, more than two months after the secret document was issued and four months after they first received word of the troubling new disease. WHO, meanwhile, recommended that travelers postpone all nonessential travel to Guangdong province and neighboring Hong Kong.

The outbreak of the illness is a revealing case study in how China's authoritarian government, which seeks to maintain a monopoly on power and control information, concealed vital data about a life-threatening disease from the Chinese people, according to doctors, health officials and journalists familiar with the events.

The people interviewed for this article include physicians in Guangdong who specialize in treatment of respiratory disease and health department sources connected to the case who spoke on condition they not be further identified. Chinese health authorities in Guangdong treated the outbreak almost as "if it did not exist," said one doctor in Guangzhou, the provincial capital. "The idea was if they pretended it wasn't there, then it would go away."

China's failure to acknowledge the outbreak and stand up to the disease reflects a long-standing policy by the Chinese state, said Li Xiguang, a former journalist for the New China News Agency and now a professor of communications at Tsinghua University.

"The Chinese government is very conservative," he said. "News such as hijackings, or earthquakes, or contagious diseases are all considered to be highly confidential. Officials want to keep 'stability,' and they are afraid that there will be chaos if people know the truth."

Stability in this case, according to Li and others, means continued foreign investment, tourism and economic growth.

But China's slow response and media blackout about a life-threatening illness has angered some Chinese, notably those in major cities, where information has been available from independent sources such as the Internet. "I won't believe the government again," said Cindy Zhang, a senior at a Beijing university.

The long-term fallout from the government's decision not to address the issue earlier is still unclear. State-run news media have already begun blaming local authorities, and not China's communist system, for the problem. "Initially, local authorities failed to inform the public of the situation. In the absence of an official voice, people's worries were heightened by rumors," said an editorial in the English-language China Daily.

The outbreak is also posing an early challenge for China's new government, led by President Hu Jintao and Premier Wen Jiabao, who have promised a government more attuned to the people's needs.

Doctors and health officials said the Chinese government knew in December that a dangerous new type of pneumonia existed in Guangdong. But only today, after weeks of international pressure, did Wen chair his first meeting of the State Council on the disease. And today was the first time that China's Center for Disease Control issued a nationwide bulletin to hospitals on how to prevent the disease from spreading.

The illness is also a test of China's new-found interest in working with international organizations. In March, China invited a team of experts from the World Health Organization to travel to China to look into the disease. Until today, however, WHO officials were not allowed to travel from Beijing to other parts of the country to investigate the SARS outbreak.

The government agreement for the visit to Guangdong province followed a week of entreaties by the WHO team. The researchers will investigate the presumed source of the disease in Guangdong and probe reports that the infection rate has slowed there. The government will allow one of its research institutes to join a global network searching for the source of the disease. It has also released its most detailed statistics yet on the disease's progress through this vast country -- 1,190 cases and 46 deaths in six provinces -- the most cases and fatalities reported in any country.

"We've been talking about setting deadlines," said James Maguire, a team member and an epidemiologist at the U.S. Centers for Disease Control and Prevention. Maguire said Guangdong's experience could be significant in the search to identify and prevent SARS. "We're extremely interested in what appears to be the waning of the infection rate in Guangdong," Maguire said.

A doctor specializing in respiratory diseases in the province credited preventive measures for the slower rate of infection, saying that hygienic measures such as the use of masks and gloves and isolation of patients began after workers returned from the Chinese New Year holiday.

Feng Shaomin, director of foreign affairs for the Guangdong health department, said the government did not act faster partly because of economic considerations -- it did not want to affect the Chinese New Year holidays when people spend vast amounts of money on food and shopping.

"The most important vacation in the life of Chinese people, the Spring Festival, was coming. We didn't want to spoil everyone's happy time," he said. "You can imagine how people would have reacted if we had told them about the disease. They wouldn't eat out, nor would they go shopping or get together with family members and friends. If we had done it earlier, it would definitely have caused chaos."

The delay in publicizing the extent of SARS had an impact on decisions made by Chen Jianchang, 78, a veteran of China's revolution.

During the Spring Festival holidays, he told his family he wanted to get a checkup. He went to the hospital in Guangzhou on Feb. 9. A day later he contracted a mysterious illness, and by Feb. 22 he was dead. His wife, Li Hua, who spent hours at his bedside, also contracted the illness. She died on Feb. 24.

A son and a daughter also got sick, but they recovered. "If we had known about this disease, we would have stayed away from the hospital," said the daughter, Chen Lili, 31. "Why didn't the government say anything? I blame them for my parents' death."

Several days after her father died, Chen Lili, a secretary, traveled to Hong Kong and checked into the Queen Elizabeth Hospital with a bad cold. "I told them that I had this terrible disease, but they did not believe me," she said. "They said they had received no information from China about this disease so we shouldn't worry about anything." Chen is still haunted by the possibility that she might have infected people in Hong Kong. "It is a horrible feeling," she said.

It is now generally agreed that the illness emerged in Foshan, 15 miles southwest of Guangzhou, in November. The illness then came to Guangzhou in January, transmitted by a shrimp salesman. The unnamed salesman was treated for pneumonia-like symptoms at three medical facilities: Zhongshan No. 2 Hospital and Guangzhou Hospitals No. 3 and No. 8.

Officials now say they think the man infected 90 people at the three hospitals, including a doctor named Liu from Zhongshan No. 2. Liu later left for Hong Kong, where he stayed at the Metropole Hotel Feb. 21-22 and is believed to have infected several people there who then took the disease overseas.

The Chinese doctors and health department officials said the illness was the subject of intense scrutiny by health authorities in Guangdong as early as December. But they said no concerted action was taken to control its spread until late January.

The sources said that even when medical workers returned from the New Year's holidays in February, the information in the top-secret document about the illness was vague. There was no mention that the disease was highly contagious and that rigorous preventive measures were required to prevent its spread.

As a result, by the end of February, 45 percent of Guangzhou's 900 cases were health care workers, sources in the city said. And communication between the province's health department and the city's health authorities was poor, doctors said.

In addition, the security designation for the top-secret document meant that Guangdong health authorities could not discuss the situation with colleagues in Hong Kong, Chinese sources said, because they risked being accused of leaking state secrets. Nor did the officials contact other provincial health departments in China.

In the absence of government direction, some communities resorted to folk remedies. In Foshan and Heyuan, two of the cities in Guangdong where the outbreak began, doctors received reports that people were using white vinegar and a Chinese herbal remedy known as Banlangen, made from the root of the indigo tree, to fight the disease. "We knew what was going on there and we thought it was ridiculous," said a doctor. "But it wasn't ridiculous. It was serious. No one told us."

The clampdown on information extended to newspapers and television. News about the outbreak was suppressed in China's state-controlled media. Reporters in China were allowed to report about the disease extensively only between Feb. 9 and Feb. 24. The Propaganda Ministry ordered the media to halt most reporting about the disease during the run-up to the National People's Congress, at which time "bad" news is rarely published.

Today the blackout apparently was lifted. Health Minister Zhang Wenkang gave a rare interview to state-run television, saying the disease was "generally under control." Nonetheless, one newspaper, Southern Metropolitan Daily, is under investigation by Guangdong provincial propaganda authorities for reporting too aggressively about the disease.

The Propaganda Ministry also stopped another newspaper from reporting about a document, issued to high-level officials in Guangdong province in early January, that warned them about the disease weeks in advance of the limited information issued to the rest of the public.

"This issue is about the corruption of power," said a senior editor of the newspaper, which had reported about the document but had its article quashed. "It made it seem like their lives were more important than the rest of us."

Chinese officials have not exhibited any regrets about the way they have dealt with the outbreak. In a closed-door meeting with senior editors early last week, Lei Yulan, a deputy governor of Guangdong province, dismissed the open information policy of other countries and Hong Kong, just over the border.

"You can see how much trouble the Hong Kong government created for itself after it made everything public," she said, according to a participant at the meeting. "They didn't have the ability to control and handle the disease, so what good was it to make everything public? Their tourism and investment are affected. Most of all, their people are in chaos. What a great loss."

Meirion Evans, left, and James Maguire of the World Health Organization speak in Beijing about a mysterious flu-like disease that has spread from China to 16 other countries.