China is rewriting the facts about Covid-19 to suit its own narrative

China has been here before. During the Sars crisis in 2002 and 2003 it hid cases, censored doctors and withheld information from the world for four months. Nearly 800 people died.

Related: EU says China behind 'huge wave' of Covid-19 disinformation

Fast forward to 2020. The successor to Sars appeared, and has so far caused 600,000 deaths and more than 15 million infections worldwide. The Chinese government says it has been “open, transparent and responsible” throughout; its critics say not open, transparent or responsible enough to avert disaster.

After Sars, China built a nationwide disease surveillance network and formidable bioscience capacity. It invested in research on bat coronaviruses. Disease control chiefs said it could stop another outbreak. But in 2020 none of these preparations were enough to offset risks coming from other directions: ever more rigid top-down politics inside China and a globetrotting population with direct international flights from Wuhan.

Last December patients started turning up in Wuhan’s hospitals with pneumonia symptoms that didn’t respond to treatment. Doctors were quick to send samples for genetic sequencing which soon revealed a coronavirus closely resembling Sars. Chinese scientists warned the new virus was also contagious, spread by respiratory droplets and on surfaces. But both in Wuhan and in Beijing, health authorities sought to minimise the story, first insisting there was no reason to suspect the virus was transmitted by humans and later that the risk was low.

Frontline doctors didn’t agree. They tried to warn each other on social media, but were swiftly silenced, some forced to sign police confessions that they had spread misinformation.

The Hong Kong microbiologist Prof Yuen Kwok-yung had helped to identify Sars back in 2003. As soon as he saw the social media posts from Wuhan, he urged the Hong Kong government to take public health precautions. He told Panorama: “If you don’t make use of every hour, you are in big, big trouble.”

Instead, from 31 December to 20 January, China’s political leaders played down the risks of the virus, squandering the lead their doctors and scientists had given them.

Beijing is naturally sensitive about its early handling of what has gone on to become a global catastrophe. At home its censorship is so overwhelming that it can control the timeline and edit the facts to suit its narrative. Since January, censors have assiduously deleted documentary evidence and added events and comments retrospectively to suggest leadership engagement. Seven months on, the silencing of doctors and scientists continues, while some Chinese citizens who have tried to preserve inconvenient facts or present a different version of the narrative have disappeared.

As a result, there is no meaningful challenge inside China to the official version of events. According to this version, as soon as Beijing had clear evidence of human transmission of the virus it publicly announced it, and prepared tough control measures including the lockdown of Wuhan on 23 January.

The truth is more complex. For example, Beijing certainly had a key part of its evidence on human transmission a week earlier than the official version admits. On 12 January, Yuen diagnosed a family with the novel coronavirus in Shenzhen, 700 miles from Wuhan. Only some members of the family had been to Wuhan. Yuen immediately alerted authorities in Beijing.

But between the beginning of the year and the lockdown, 5 million people left Wuhan for destinations in China and beyond. Prof Andrew Tatem of the University of Southampton told Panorama: “If the same interventions that were put in place on 23 January had been put in place on 2 January, we may have seen a 95% reduction in the number of cases.”

The Chinese ambassador to the UK, Liu Xiaoming, told the BBC: “The Chinese health authorities notified WHO on 31 December in the shortest possible time.” In fact it was the WHO that had picked up reports of the outbreak on the internet – and on 1 January sought answers from the Chinese government. China responded two days later.

China’s response time has been much faster than during the Sars outbreak 17 years ago, but most close observers of the Chinese Communist party say full transparency is never its first instinct and that under the leadership of Xi Jinping, information control has grown ever tighter. Challenged on the silencing of doctors and scientists in early January, a key government adviser, Prof Li Lanjuan, told us: “To announce its contagiousness, if it is not yet confirmed, would cause public panic. Therefore we must be responsible to the public, and ascertain the facts first.”

Some governments have demanded an international investigation in China to determine the origins and early spread of the virus. The Chinese government says it will join a global inquiry into the pandemic but only when the crisis is over. It says it should not be blamed as it is a victim too, and that its tough measures to combat the Wuhan outbreak prevented hundreds of thousands of infections and bought the world time.

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Dr Ali Khan spent much of his career in the US Centers for Disease Control and says the world now needs to think ahead. “We can’t afford to do this again. If … some countries having an outbreak [are] deciding to not share that information, there have to be consequences.”

But what consequences? The WHO’s regulations on protecting against the international spread of disease are legally binding, but there are no sanctions for countries that fail to adhere to them. In recent weeks, western governments have begun adopting a tougher tone towards Beijing on a range of issues, but there is little sign of a concerted international push for new WHO inspection powers to tackle future disease outbreaks. Indeed, the US has just withdrawn funding for the WHO, alleging that the global health body served as Beijing’s puppet during the early stages of coronavirus.

For now, we are left hoping that China’s leadership has learned its own lessons about the need to act faster to protect its own public and the world.

• Carrie Gracie is a BBC newsreader and presenter and former China editor for BBC News

Panorama: China’s Coronavirus Cover-Up is on BBC One, Monday 27 July, 7.30pm