Chinese paramilitary police and security officers wear face masks as they stand guard outside an entrance to the Forbidden City in Beijing on Friday. Photo / AP
On December 31, 2019, the World Health Organisation's (WHO) China office heard the first reports of a previously-unknown virus behind a number of pneumonia cases in Wuhan.
Four months later, as the battle against Covid-19 rages on, the weeks leading up to that date have become the source of fierce scrutiny, with the Chinese government facing accusations of deception surrounding the disease's early spread.
As we head into the fifth month of a global crisis described as the worst since World War 2, the mystery surrounding how the world only learnt of Covid-19's severity once its rapid spread had already begun has fuelled a push for a probe into China's handling of the disease.
The call for answers comes amid recent findings that one Chinese scientist had issued a chilling public warning on the risk of bat-borne virus pandemics some years before the current outbreak.
A censored messaging app, a reprimanded whistleblower and a scientist known as "batwoman" are just some of the puzzle pieces that have slowly trickled out from the origin of the deadly coronavirus – all of which indicate medical knowledge of human-to-human transmission was quashed over crucial days in December.
Here's what we know:
First coronavirus case and reports
The first case of Covid-19 reportedly traces back to November 17, 2019, more than a month earlier than the alert to the WHO.
While a clear "patient zero" has not been identified, a 55-year-old individual from the Hubei province in China is the first known person to contract the disease, according to unpublished Chinese government data reported by the South Morning China Post.
The report said Chinese authorities had identified at least 266 people who contracted the virus last year and who came under medical surveillance, the earliest being the case detected in mid-November.
Official statements by the Chinese government to the WHO, however, say the first confirmed case had been diagnosed on 8 December, reported the Guardian.
On January 11, Chinese state media reported the first known death from the virus — a 61-year-old man who was a regular customer at the market in Wuhan.
It was nine days later, on January 20, that Chinese president Xi Jinping first publicly addressed the issue of the virus, saying it had to be "resolutely contained".
Wuhan was locked down on January 23.
The spread
The first case outside of China was reported by the WHO in Thailand on January 13. It was a woman who had arrived in the country from Wuhan.
Over the following days, authorities in the US, Nepal, France, Australia, Malaysia, Singapore, South Korea, Vietnam and Taiwan confirmed cases of their own.
A 44-year-old man in the Philippines, who had travelled to Wuhan, was the first to die outside China on February 2nd.
By this point, China had reported more than 360 deaths.
By early May more than 200,000 people have died, and 3.2 million infections have been confirmed in at least 187 countries and territories, with the United States overtaking China as the new epicentre of the pandemic in late March.
As of Friday, the death toll in the US stood at over 60,000, with more than 1 million infections. In New York City, hospitals are groaning under the weight of new cases as they continue to double every three days.
'Batwoman' and prior knowledge of virus
This week, reports of a Chinese scientist's chilling prediction on the risk of future bat-borne virus pandemics came to light.
Dubbed the "Batwoman" of Wuhan by her colleagues after years of virus-hunting expeditions in bat caves, Shi Zhengli has been warning the world for years that the wildlife trade of bats, civets, and other animals was a recipe for disaster.
Five years ago, she was a co-author of a paper that contained a public warning that the SARS virus outbreak "heralded a new era in the cross-species transmission of severe respiratory illness with globalisation leading to rapid spread around the world and massive economic impact."
"Although public health measures were able to stop the SARS-CoV outbreak, recent metagenomics studies have identified sequences of closely related SARS-like viruses circulating in Chinese bat populations that may pose a future threat,'' the paper stated.
Dr Shi is now at the centre of a diplomatic war of words between the US and China over claims the Chinese government "covered up" her Covid-19 discoveries during a critical week in January.
She was among the first scientists in the world to learn Covid-19 was killing people in her hometown of Wuhan after authorities asked her team to analyse blood samples on December 30.
On February 3, her team was the first to publicly report the mystery virus in Wuhan was a bat-derived coronavirus.
However, Dr Shi was ordered not to disclose information on the disease.
In an email to Dr Shi and key officials in January, Yanyi Wang, the director of the Wuhan Institute of Virology warned "inappropriate and inaccurate information" was causing "general panic". Wang added that the National Health Commission "unequivocally requires that any tests, clinical data, test results, conclusions related to the epidemic shall not be posted on social media platforms, nor shall (it) be disclosed to any media outlets including government official media".
It was at this time that Dr Shi had made key inroads into identifying the disease and the danger of its transmission.
Gao Yu, a Chinese journalist freed last week after 76 days of lockdown in Wuhan, said he spoke to Dr Shi during his incarceration and revealed: "We learned later her institute finished gene-sequencing and related tests as early as January 2 but was muzzled."
And in an online lecture last month, Shi herself said her team confirmed on January 14 that the virus they had identified could infect people – six days before this fact was revealed by China.
This week, reports of a Chinese scientist's chilling prediction on the risk of future bat-borne virus pandemics came to light.
Dubbed the "Batwoman" of Wuhan by her colleagues after years of virus-hunting expeditions in bat caves, Shi Zhengli has been warning the world for years that the wildlife trade of bats, civets, and other animals was a recipe for disaster.
The lab theory
Amid reports Western intelligence agencies are examining her work, Dr Shi maintains Covid-19 was not accidentally unleashed as a result of poor safety standards.
But in an interview with a US science magazine, she admits to "sleepless nights'' when the outbreak first began.
Given her initial studies suggested the subtropical provinces of Guangdong, Guangxi and Yunnan had the greatest risk of coronaviruses jumping to humans from animals — particularly via bats — she remembers thinking, "could they have come from our lab?".
"I wondered if (the municipal health authority) got it wrong," she said. "I had never expected this kind of thing to happen in Wuhan, in central China."
As Shi and her colleagues raced to uncover the source of the contagion of the mystery illness against a mounting death toll, Shi was also investigating whether there was a link within her own work.
According to Scientific American, "Shi breathed a sigh of relief when the results came back: none of the sequences matched those of the viruses her team had sampled from bat caves".
However, an exclusive investigation by the Daily Telegraph has revealed Five Eyes intelligence agencies of Australia, Canada, NZ, UK and US, are looking closely at the work of Shi and a senior scientist at the Wuhan Institute of Virology, Peng Zhou.
It follows a report in the Washington Post that US embassy scientists and diplomats in Beijing visited the laboratory and met with Shi.
They then sent warnings back to Washington about inadequate safety practices and management as it conducted research on coronaviruses from bats.
According to the Post, the cable "warns that the lab's work on bat coronaviruses and their potential human transmission represented a risk of a new SARS-like pandemic".
On April 30 US intelligence agencies said federal agencies agreed with the "wide scientific consensus that the Covid-19 virus was not man made or genetically modified."
However they said the intelligence community would "continue to rigorously examine emerging information and intelligence to determine whether the outbreak began through contact with infected animals or if it was the result of an accident at a laboratory in Wuhan."
US President Donald Trump has also speculated that China unleashed the virus on the world by "mistake".
On Thursday, he said the US was finding out "whether they made a mistake or whether it started off as a mistake and then they made another one, or did somebody do something on purpose."
'Whisteblower' Dr Li Wenliang
Before Yanyi Wang's email muzzling Dr Shi circulated in January, another group of doctors aware of an impending pandemic were promptly silenced.
A small WeChat group run by Wuhan Red Cross hospital Dr Li Wenliang warned colleagues of confirmed cases of a contagious coronavirus at another hospital on December 30.
He told colleagues that patients were being "quarantined in the emergency department".
"Wash your hands! Face masks! Gloves!" the 33-year-old medic wrote.
But technology implemented by the Cyberspace Administration of China scoured the social media platform and buried any information raising the alarm within the private conversation, going on to censor any keywords related to illness on the messaging app, the BBC reported.
Dr Li was then jailed and forced to sign a declaration which accused him of making false statements that disturbed the public order.
He died from the very illness he tried to warn the country about on February 7.
China's first report claims
Despite all this, Dr Zhang Jixian, head of the respiratory department at Hubei Provincial Hospital, has been hailed by China as the first person to report the pathogen to authorities on December 27.
Her account aligns with Dr Li's, as well as the timeline given by the WHO, which said it was alerted to the outbreak on December 31.
Dr Zhang Jixian's claims over the earliest days of the outbreak were published by China's state-run Xinhua news agency in April, as the country began to face mounting accusations of a cover-up and was forced to revise the number of dead in Wuhan up by 50 per cent.
Speaking through a bright blue surgical face mask, Dr Zhang told Xinhua the first two coronavirus patients had been an elderly husband and wife.
"On December 26, the first patient we saw was an elderly lady who had fever, cough and trouble breathing," she said.
"Her husband and son came along with her. Her husband came to see a doctor for fatigue. He didn't have a fever … We wondered whether the son was sick as well. Once we did the test, sure enough, the son had the lung problem too."
Dr Zhang said the family's symptoms "looked like flu or common pneumonia" but their CT scans showed significant damage to their lungs.
"We've had patients with ground-glass opacities in their lungs caused by virus infection. But his (the son's) were a lot more and larger than what we had seen before," she said.
When another patient presented with the same symptoms on December 27, Dr Zhang said she filed a report to the hospital that warned she'd likely "discovered a viral disease, probably infectious".
Dr Zhang told reporters that CDC workers came to her hospital to carry out research on the same day, calling their reaction "very timely".
She added that she did not expect the contagion to end up spreading so widely.
What's next
With the "batwoman" revelations in particular fuelling fresh concerns over China's alleged cover-up, critics are arguing that Communist Party chiefs thwarted efforts to contain the outbreak before it exploded around the world.
Australia has emerged as one of the most vocal critics of Beijing as it calls for an investigation into the origins and spread of the virus.
The prime minister, Scott Morrison, has attempted to rally member nations of the WHO to support an independent inquiry into the origins and spread of the coronavirus. He has said Australia will push for an international investigation at the WHO assembly on May 17.
But China is seemingly unwilling to co-operate and has issued veiled threats over whether Chinese citizens would continue to travel to Australia and purchase the country's products.
This week, the state-controlled People's Daily lashed out at Scott Morrison as deserving "a slap in the face" for trying to blame the Covid-19 pandemic on the communist state, warning any push for an independent inquiry into the virus' origins will spark a travel and trade boycott.
It comes after reports that China is clamping down on publication of academic research about the origins of coronavirus, in what the Guardian reported is likely part of a wider attempt to control the narrative surrounding the pandemic.