In the days before April 17, the two new leaders of China struggled with the profound question of whether to break with Communist Party orthodoxy and reveal the rampant spread of a dangerous virus.

President Hu Jintao and Premier Wen Jiabao, who had been in power only since March 19, faced a grave crisis. If they did nothing, they risked loss of control over information, lower economic growth and social instability. If they acknowledged a coverup but failed to beat back the virus, they risked losing power to an elder leader and his allies waiting in the wings.

On April 17, Hu took the plunge. During an unscheduled meeting of the all-powerful Politburo of the Communist Party, he acknowledged the government had lied about the disease and committed the Communist Party to an all-out war against an epidemic sweeping the capital and the country. Three days later, China's Communist leadership carried out its most significant political purge since the crackdown around Tiananmen Square in 1989. The capital's mayor and the country's health minister were fired for covering up the epidemic of severe acute respiratory syndrome, or SARS.

What forced Hu's hand? According to dozens of people interviewed for this article, the new Chinese leadership faced immense pressures from abroad and inside the country. The World Health Organization and the foreign media clamored for accountability. A whistleblower exposed lies about the outbreak. China's people began demanding basic rights to information. In the hospitals, the virus crept into the ranks of the Communist Party. And, unlike in times past, the drama was chronicled in real time by short-text messages on mobile phones.

The combined pressures on Hu reflect the tumultuous pace of change in contemporary China, from technology that often outpaces efforts to control information, to globalization and foreign influences that vie with Communist Party doctrine.

Hu was an unlikely candidate to order an about-face in party policy. A 59-year-old hydrologist, he spent more than a decade waiting to succeed Jiang Zemin as president and was known for one distinguishing characteristic -- extreme caution. Moreover, more than half of China's all-powerful nine-member Standing Committee of the Politburo, which Hu theoretically leads, were men loyal not to him but to his elderly predecessor. And Jiang, according to numerous Chinese sources, was not in favor of openness.

However, the epidemic was such a shock to China's system that it provided an opening for Hu. Many Chinese have compared the outbreak of the virus to the Sept. 11, 2001, terrorist attacks against the United States. Like President Bush, they said, President Hu was new in office and struggling for a purpose. Fighting the virus gave that to him.

Whether the decision by Hu to confront the outbreak will lead to China getting SARS under control is not known. The disease is still spreading rapidly, although the rate of infection appears to be slowing in Beijing. As of today, China had 5,013 SARS cases; 252 people in China have died from the disease.

'A Fatal Flu'

Severe acute respiratory syndrome erupted in Guangdong province in southern China in November. Authorities knew about the spreading pathogen at the latest by Jan. 1, when a provincial health team was dispatched to Heyuan city, 100 miles northeast of the provincial capital Guangzhou, to look into a case at the People's Hospital there.

A shrimp salesman had already infected five people at the hospital and went on to infect scores more in hospitals in Guangzhou. It is unclear what authorities in the province did with this information during the month of January -- whether they contacted the central government in Beijing, or what they said. But the provincial government waited almost a month to begin warning hospitals in Guangdong about the outbreak. When it did, the warnings were not clear, doctors in the province said. The reason, Guangdong authorities later acknowledged, was that provincial authorities did not want concerns about the virus to cut into people's spending during the Chinese New Year holiday at the end of January.

Provincial authorities said this type of behavior was justified. They were accustomed to maintaining a monopoly on power and information.

On Feb. 7, the province reported the outbreak to central authorities in Beijing, according to the Southern Daily, the official newspaper of the Communist Party in the province. Chinese sources said the provincial report was read by members of the Politburo's Standing Committee in Beijing. Further evidence that the central government was aware of the virus's spread came on Feb. 9, when, responding to the provincial report, the central government dispatched a team of health officials, led by Deputy Health Minister Ma Xiaowei, to look into the outbreak.

Meanwhile, the virus was running wild, tearing through the ranks of health care workers. At one point, there were 900 people sick with SARS in Guangzhou and 45 percent of them were health care professionals, doctors in the city said.

News of the disease reached the Chinese public in Guangdong through a short-text message, sent to mobile phones in Guangzhou around noon on Feb. 8. "There is a fatal flu in Guangzhou," it read. This same message was resent 40 million times that day, 41 million times the next day and 45 million times on Feb. 10, according to the Southern Weekend newspaper, published in Guangzhou.

News spread as well through Internet chat rooms favored by China's urban youth and e-mails about the virus, forwarded from person to person.

The messages were an unprecedented challenge to the state's monopoly on information.

Despite the outbreak and worries about the virus among the public, editors at several newspapers said the provincial party secretary, Zhang Dejiang, continued to impose a ban on news media reporting about the disease.

But on Feb. 11, the media silence was broken. The Guangzhou Daily reported that the virus had infected 305 people and that five had died. Sources said the paper was able to defy Zhang's blackout because it had finagled permission from the provincial government, which defied the orders of the party boss. Sources said the permission to publish the news came directly from Huang Huahua, the provincial governor, who is an ally of President Hu. By contrast, Zhang is loyal to Hu's predecessor, Jiang.

The day the Guangzhou Daily's story appeared, the provincial government called a news conference. When journalists asked the provincial health chief why he had not reported the outbreak sooner, he said "it was fine not to tell the public" because he was not legally required to do so.

Epidemics are considered state secrets in China. In the early days of the 1949 revolution, reporting on epidemics was a crime because it called into question the quality of China's system. Now, the government suppresses such reports because they could discourage foreign investment.

Following the news conference, Zhang's propaganda bureau again tried to control the media. But the tussle between Zhang, the party secretary, and Huang, the governor, had created a space. Also, Chinese sources said, Hu stepped into the fray, ordering that Guangdong's media be given room to report adequately about the virus. What followed was a week-long open period for the media in Guangdong province. Reports on the illness were fast and furious and called into question the government's handling of the outbreak. One weekly, 21st Century World Herald, devoted eight pages of one edition to the topic.

On Feb. 23, Zhang's propaganda bureau, arguing that too much criticism could influence "stability," reimposed the media ban. By that time, SARS had spread to Hong Kong and would soon move around the world. The ban stayed in place for more than a month.

A Torrent of Messages

Quietly, Guangdong began to fight the outbreak. But because the party had banned any public talk of the spreading virus, doctors around the country had no idea what was waiting for them.

The microbe was on the move. In late February, a jewelry dealer got sick in Guangdong and returned home to Shanxi province, in central China, 1,000 miles to the north. She visited hospitals in the provincial capital, and then, unable to get decent care, went to Beijing's No. 301 military hospital. By that time she had infected her husband and parents. By early March, her parents were dead. The virus began spreading in Beijing's hospitals.

On March 5, the National People's Congress, China's national legislature, opened in Beijing. The annual meeting was of particular importance because it marked the beginning of a new government, with a new president, Hu, and premier, Wen. The government banned all negative news reports during the legislative session, wanting to ensure that all eyes were on the tightly choreographed political succession from the elder generation of Jiang to the new leaders.

As the virus infected more and more people, the Health Ministry held a meeting with the heads of major Beijing hospitals on March 9 to inform them about SARS and to emphasize that they were not to report the spread of the disease to any media outlets, Chinese sources said.

All the preparations, however, could not completely squash talk of the virus. It came up in an oblique way at the legislative session. A group of 30 delegates from Guangdong province offered a motion to establish a nationwide epidemic prevention network -- a circuitous signal of their concern. The Southern Metropolitan News, a scrappy Guangzhou-based tabloid, published a piece on March 6 that contradicted the government line that the virus was under control in Guangdong. The piece enraged Guangdong party chief Zhang, who forced the paper to pull its reporter from Beijing and threatened to shut the paper down, media sources said.

Then, on March 15, three days before the close of the legislative session, the World Health Organization issued its first global warning about the virus. China's central Propaganda Ministry ordered China's media not to report the warning. The editor-in-chief of a Beijing-based newspaper said the order came from the Politburo. "They knew very clearly how fast SARS was spreading," he said.

Still, information about the virus was filtering into mobile phones and computers. Text messaging between cellular telephones has become an enormously popular way for Chinese to communicate because it is fast, and the nature of the Chinese language lends itself to short messages that can convey a lot of information. While authorities had banned press reporting about the disease, text messaging was relatively uncensored.

In the first quarter of the year, Chinese zapped a total of 26.5 billion messages to each other, a 15 percent increase over the same period last year. A lot of those messages concerned the U.S. war plans on Iraq. Many more, Chinese telecommunications sources said, concerned SARS. "Foreign reports: SARS has reached Beijing," read one. "Foreign reports: Two dead in Beijing from SARS," read another.

While the word of the outbreak was reaching people, the virus itself was reaching into the Communist Party and China's government, adding a different, more personal pressure on officials to act. As of today, 11 officials from central party agencies have died from SARS, Chinese sources said.

A team of experts from the World Health Organization arrived in Beijing on March 23. Three days later, the Chinese government for the first time acknowledged that the virus had spread outside of Guangdong province, saying eight people had contracted it in Beijing. The real numbers were well into the hundreds, doctors said.

The price of doing nothing was beginning to cost China. On April 2, WHO issued the first travel advisory in its 55-year history, advising people not to go to Guangdong and Hong Kong. On April 3, Health Minister Zhang Wenkang said at a news conference that China was "safe" and that "SARS has been placed under effective control."

He said Beijing had only 12 cases of SARS.

Hu Makes His Move

On April 4, Jiang Yanyong, a 72-year-old retired surgeon at Beijing's No. 301 military hospital, took an enormous risk. And with that risk he put more pressure on the Communist leadership. Jiang had watched Zhang's news conference and become enraged, he recalled. He sent an e-mail to China Central Television and the Hong Kong-based Phoenix television station, accusing Zhang of lying. In the message, Jiang Yanyong said that just within the hospitals he knew of in Beijing, there were more than 100 cases of patients with the virus and six had died.

Neither station followed up on the e-mail, but it was leaked to Time magazine, which put the information on its Web site on April 9. Time's report and a large number of other articles from the Western press were translated and sent to e-mail boxes all over China.

"We got our information from the Web, and the Web said the government's information was fake," said a senior government official, speaking on condition of anonymity for fear of losing his job. "The first thing we all did when we got to the office was log on and read what the government said and then read what the foreign media said. They had created a situation like this: If you don't speak the truth, people will start believing foreigners. So the government had to change."

There was now a confluence of factors bearing down on China's leadership. President Hu and Premier Wen had been in office only a few weeks. Officials loyal to the previous president, Jiang Zemin, were opposing any bold plan to change position on the epidemic and release more information, Chinese sources said. But the epidemic was worsening. There were signs it was spreading into China's interior and fresh indications it was affecting China's international prestige.

On April 7, Pekka Aro, a Finnish official at the International Labor Organization, became the first foreigner to die of the disease in China. His death increased international pressure on China; foreign business people began to express concern to Chinese officials. Foreigners were canceling business trips. The World Health Organization had begun to embarrass China by stating bluntly that Beijing was covering up the extent of the epidemic.

"It was obvious that drastic measures needed to be taken," said another senior government official. "And this was a great opportunity for Hu to distinguish himself from Jiang."

Wen, the premier, visited China's Center for Disease Control on April 7. The official New China News Agency report of that visit was all smiles and handshakes. But in reality, Wen had come to deliver a stern message, witnesses said. "He talked about the military," said a witness. "He said it was wrong that the military was not reporting cases of SARS. He said we have to start telling the truth to the people. He asked us how many people had SARS in Beijing. We couldn't tell him."

China's military had not been reporting to the government its numerous SARS patients in the capital. Instead it had been reporting up the military chain of command that ended with Jiang, who, despite having stepped down as president, remained chief of the military.

Hu and Wen's push for change began gathering momentum. On April 9 and 10 they arranged for experts and respected non-members of the party to meet with senior government and party officials to discuss the crisis. The consensus from those meetings, according to participants, was that China should stop covering up its epidemic and begin working closely with WHO and other agencies to deal with the virus.

On April 11, Hu left the capital and headed to the front line of the battle against the virus in Guangdong. "Hu's trip followed a model for Communist political struggle," said a Chinese journalist who accompanied him. "To make a point, you have to leave the capital." At about the same time, Jiang Zemin slipped away from Beijing to Shanghai, his political stronghold, a move that would hurt him later when critics would say that he was running from the virus.

While Hu was still in Guangdong, Premier Wen chaired an emergency meeting of the State Council on Sunday, April 13. He warned that the country's economy, international image and social stability could be affected and that "the overall situation remains grave."

On April 17, the Politburo met in an extraordinary session in Beijing. Hu and Wen had spent more than 10 days preparing for the confrontation. Hu ordered China's officials to stop lying about the extent of the SARS epidemic sweeping the country and vowed an all-out war against the disease. The orders appeared on the front page of every Chinese newspaper the next day.

On April 20, Health Minister Zhang Wenkang and Beijing's mayor, Meng Xuenong, were ousted.

While some are predicting a new era of openness from China's Communists, there is also evidence to the contrary. Chinese authorities have arrested 107 people in the past week for sending "rumors" via the text messaging system used on Chinese mobile phones. And as Henk Bekedam, head of the WHO office in Beijing, said, "A lot of those rumors turned out to be true."

Six days after the firings, Jiang reemerged and claimed the country had made great strides against the virus, a message that clashed with the grave tone of those delivered at the time by Hu.

"The battle is not over yet," said a Western ambassador, noting that Jiang, as chairman of the Central Military Commission, still controls the army. "Jiang is a very smart politician," he said. "And SARS is not finished yet."

A Beijing policeman hugs a resident to celebrate the end of a two-week quarantine, imposed on thousands to fight the spread of SARS. April 3: At a news conference in Beijing, Health Minister Zhang Wenkang declares that China is "safe" and that "SARS has been placed under effective control."

April 14: President Hu Jintao talks with workers at a medical facility in Guangzhou, capital of the southern province of Guangdong, where the outbreak originated.

April 26: Premier Wen Jiabao and new Health Minister Wu Yi, center, talk with masked workers at a Beijing market, days after the previous health minister's firing.

Couples bade farewell Sunday as some began quarantine at Nanjing Normal University. The eastern city has quarantined nearly 10,000 people in an effort to stop SARS. Man at right uses a text-messaging phone, which is how much news of SARS initially became known.Former president Jiang Zemin, left, has claimed that China had made great strides against SARS, contrary to remarks by his successor, Hu Jintao.