In the six days after top Chinese officials secretly determined they likely were facing a pandemic from a new coronavirus, the city of Wuhan at the epicentre of the disease hosted a mass banquet for tens of thousands of people, and millions began travelling through the city for Lunar New Year celebrations.

President Xi Jinping warned the public on the seventh day, Jan. 20. But by that time, more than 3,000 people had been infected during almost a week of public silence, according to internal documents obtained by The Associated Press and expert estimates based on retrospective infection data.

That delay from Jan. 14 to Jan. 20 was neither the first mistake made by Chinese officials at all levels in confronting the outbreak, nor the longest lag, as governments around the world have dragged their feet for weeks and even months in addressing the virus.

"This is tremendous," said Zuo-Feng Zhang, an epidemiologist at the University of California, Los Angeles. "If they took action six days earlier, there would have been much fewer patients and medical facilities would have been sufficient. We might have avoided the collapse of Wuhan's medical system."

The Chinese government has repeatedly denied suppressing information in the early days, saying it immediately reported the outbreak to the World Health Organization.

"Those accusing China of lacking transparency and openness are unfair," foreign ministry spokesperson Zhao Lijian said Wednesday when asked about the AP story.

China in mid-April has reported a total of 3,342 deaths from the virus among 82,341 cases, though it has faced questions about how it counts and reports cases. Around 3,000 people remain hospitalized with COVID-19, or are under isolation and monitoring for showing signs of the illness or testing positive but not displaying symptoms.

Other experts noted that the Chinese government may have waited on warning the public to stave off hysteria, and that it did act quickly in private during that time.

But what is clear, experts say, is that China's rigid controls on information, bureaucratic hurdles and a reluctance to send bad news up the chain of command muffled early warnings. The punishment of eight doctors for "rumour-mongering," broadcast on national television on Jan. 2, sent a chill through the city's hospitals.

Here is a look at how the crisis played out in China from the internal documents:

Jan. 13: Thailand case raises concerns in China

For almost two weeks, China's Center for Disease Control did not register any cases from local officials, internal bulletins obtained by the AP confirm. Yet during that Jan. 5-17 period, hundreds of patients were appearing in hospitals not just in the city of Wuhan but across the country.

Doctors and nurses in Wuhan told Chinese media there were plenty of signs that the coronavirus could be transmitted between people as early as late December. Patients who had never been to the suspected source of the virus, the Huanan Seafood Market, were infected. Medical workers started falling ill.

But officials obstructed medical staff who tried to report such cases. They set tight criteria for confirming cases, where patients not only had to test positive, but samples had to be sent to Beijing and sequenced. They required staff to report to supervisors before sending information higher, Chinese media reports show. And they punished doctors for warning about the disease.

The Wuhan Huanan Wholesale Seafood Market is seen on Jan. 21. By that time, expert teams had been investigating the cluster of virus cases from the market for two weeks, but they appear to have not widened their probe elsewhere in Wuhan. (Dake Kang/The Associated Press)

An expert team dispatched from the central health agency on Jan. 8 failed to unearth any clear signs of human-to-human transmission in Wuhan. Yet during their stay, more than half a dozen doctors and nurses had already fallen ill with the virus, a retrospective China CDC study published in the New England Journal of Medicine would later show.

The teams looked for patients with severe pneumonia, missing those with milder symptoms. They also narrowed the search to those who had visited the seafood market — which was in retrospect a mistake, said Benjamin Cowling, an epidemiologist at the University of Hong Kong who flew to Beijing to review the cases in late January.

The muffling of warnings left top leaders in the dark. It took the first confirmed case outside China, in Thailand on Jan. 13, to jolt leaders in Beijing into recognizing the possible pandemic before them.

An internal memo cites China's top health official, Ma Xiaowei, as saying the situation had "changed significantly" because of the possible spread of the virus abroad.

Jan. 15: Warning to regions, with a caveat

The memo, on a secret Jan. 14 teleconference held by Ma, shows that Chinese officials were deeply alarmed and had come to a much grimmer assessment than they were letting on in public.

For weeks, officials had stuck to the line that there was "no clear evidence of human-to-human transmission," calling the disease "preventable and controllable."

But during the teleconference, Ma said that "clustered cases suggest human-to-human transmission is possible."

"The epidemic situation is still severe and complex, the most severe challenge since SARS in 2003, and is likely to develop into a major public health event," the memo cites Ma as saying.

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After the teleconference, officials adjusted their language slightly, but continued to downplay the threat.

"We have reached the latest understanding that the risk of sustained human-to-human transmission is low," Li Qun, the head of China CDC's emergency centre, told Chinese state television on Jan. 15.

In response to the teleconference, the CDC in Beijing initiated the highest-level emergency response internally, level one, on Jan. 15.

It assigned top CDC leaders to 14 working groups tasked with getting funds, training health workers, collecting data, doing field investigations and supervising laboratories, an internal CDC notice shows. The National Health Commission also distributed a 63-page set of instructions to provincial health officials, obtained by the AP.

The instructions ordered health officials nationwide to identify suspected cases, hospitals to open fever clinics, and doctors and nurses to don protective gear. They were marked "internal" — "not to be spread on the internet" and "not to be publicly disclosed."

No public warning for Lunar New Year

Before the teleconference, health authorities had focused narrowly on Wuhan.

They searched for visitors to a market that dealt in live game, believing the virus was largely transmitted from animals to humans. But rattled by the case in Thailand, Chinese leaders launched a nationwide hunt to find cases, the documents show.

The memo warned the risk of transmission was higher with many people travelling for the upcoming Lunar New Year holiday. "All localities must prepare for and respond to a pandemic," it said.

A worker walks along a corridor leading to wards at the Leishenshan Hospital, which was constructed in a parking lot from prefabricated modules in two weeks in Wuhan, in central China's Hubei province, to address the rise in infections. The hospital officially closed on April 9 but still has a small number of patients, mainly elderly with underlying complications. (Ng Han Guan/The Associated Press)

Officials in Hubei province, where Wuhan is located, were instructed to begin temperature checks at transportation hubs and cut down on large public gatherings.

The public was not warned, even as the new measures began to turn up hundreds of cases across the country and thousands of people dined at a mass Lunar New Year banquet in Wuhan.

In the memo, Ma demanded officials unite around Xi. It made clear that social stability was a key priority during the long lead-up to China's two biggest political meetings of the year in March.

"Emphasize politics, emphasize discipline, emphasize science," the memo cites Ma as saying.

Jan. 20: Xi goes public

On Jan. 20, President Xi issued his first public comments on the virus, saying the outbreak "must be taken seriously" and every possible measure pursued.

A leading Chinese epidemiologist, Zhong Nanshan, announced for the first time, on national television, that the virus was transmissible from person to person. If the public had been warned a week earlier to take actions such as physical distancing, mask wearing and restricting travel, cases could have been cut by up to two-thirds, one paper later found.

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Wuhan's case count had climbed exponentially by the time of Xi's comments — four on Jan. 17, then 17 the next day and 136 the day after. Across the country, dozens of cases began to surface, in some cases among patients who were infected earlier but had not yet been tested. In Zhejiang, for example, a man hospitalized on Jan. 4 was only isolated on Jan. 17 and confirmed positive on Jan. 21. Shenzhen, where Yuen had earlier found six people who tested positive, finally recorded its first confirmed case on Jan. 19.

The Wuhan Union Hospital, one of the city's best, held an emergency meeting on Jan. 18, instructing staff to adopt stringent isolation — still before Xi's public warning.

An earlier warning could have saved lives, said Zhang, the doctor in Los Angeles.

However, other health experts said the government took decisive action in private given the information available to them.

"They may not have said the right thing, but they were doing the right thing," said Ray Yip, the retired founding head of the U.S. Centers for Disease Control's office in China. "On the 20th, they sounded the alarm for the whole country, which is not an unreasonable delay."

If health officials raise the alarm prematurely, it can damage their credibility — "like crying wolf" —and cripple their ability to mobilize the public, said Cowling, the epidemiologist in Hong Kong.

Rewriting history, and a blame game

By late January, boiling public anger over China's initial handling of the outbreak put the leadership on the defensive. Health experts accused Wuhan's leaders of a coverup, and Beijing fired local officials.

National leaders began to publicize directives they had earlier made in secret in apparent attempts to demonstrate they had acted decisively from the beginning. On Feb. 17, Xi revealed he had led the response as early as Jan. 7, two weeks before his first public comment on the virus. Days later, the National Health Commission published a notice revealing its confidential teleconference, dated to Jan. 14.

Workers are seen at a production line for masks at the Wuhan Zonsen Medical Products Co. Ltd. in Wuhan, in central China's Hubei province, on April 12. China won't restrict exports of medical goods needed to fight the coronavirus pandemic, a government spokesperson said Thursday, amid global tension over scarce masks and ventilators. (Ng Han Guan/The Associated Press)

The public notice omitted sections of the internal memo showing how alarmed officials had been at the time. It added lines suggesting that commission leaders were responding proactively to what then seemed a minor outbreak.

In the weeks after the severity of the epidemic became clear, some experts accused Wuhan officials of intentionally hiding cases.

"I always suspected it was human-to-human transmissible," said Wang Guangfa, the leader of the second expert team, in a Mar. 15 post on Weibo, the Chinese social media platform. He fell ill with the virus soon after returning to Beijing on Jan. 16.

Wuhan's then-mayor, Zhou Xianwang, blamed national regulations for the secrecy.

"As a local government official, I could disclose information only after being authorized," Zhou told state media in late January. "A lot of people didn't understand this."

It wasn't just Wuhan. In Shenzhen, hundreds of miles away in southern China, a team led by microbiologist Yuen Kwok-yung used its own test kits to confirm that six members of a family of seven had the virus on Jan. 12. In an interview with Caixin, a respected Chinese finance magazine, Yuen said he informed CDC branches "of all levels," including Beijing. But internal CDC numbers did not reflect Yuen's report, the bulletins show.

Some world leaders turned blind eye to outbreak

The delay may support accusations by U.S. President Donald Trump that the Chinese government's secrecy held back the world's response to the virus.

However, even the public announcement on Jan. 20 left the U.S. nearly two months to prepare for the pandemic. Given the Trump administration's often bellicose and skeptical stance toward China in the previous three years, it's not clear earlier knowledge would have changed its approach.

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After Jan. 20, Trump ignored the warnings of his own staff and dismissed the disease as nothing to worry about, while the government failed to bolster medical supplies and deployed flawed testing kits.

Trump defenders have pointed to his impeachment trial in the Senate as diverting his attention, but he was acquitted in early February, holding six more campaign-style rallies and dismissing the possibility the virus would spread extensively in the U.S.

Leaders across the world turned a blind eye to the outbreak, with British Prime Minister Boris Johnson calling for a strategy of "herd immunity" — before falling ill himself.

Brazilian President Jair Bolsonaro sneered at what he called "a little cold."

According to tracking by Johns Hopkins University in Maryland, there were over two million reported COVID-19 cases worldwide as of early in the day on April 16, with about 138,500 coronavirus-related deaths.