The pavement outside Wuhan’s virology institute was lined with security guards and plainclothes officers when the convoy of government cars carrying the World Health Organization team arrived at the home of China’s highest level biosafety laboratory.

With the international press looking on, it was a tense moment for the foreign ministry officials and local government staff last week who have shadowed the scientists since they arrived in January. As his vehicle was driven past, Peter Daszak, a member of the WHO delegation, wound down the car window to assure the assembled press that the team was “asking all the questions that need to be asked”.

Chinese authorities insist they are co-operating fully with the WHO study into the origins of the Sars-Cov-2 virus that caused the Covid-19 pandemic. But Beijing’s tight grip on the visit, the time limitations placed on fieldwork and the fact they arrived more than a year after the virus was detected in Wuhan have fed doubts over whether they can answer a politically charged and scientifically difficult question.

Piers Millett, former deputy head of the support unit for the UN Biological Weapons Convention, cautioned against placing high expectations on the WHO investigators, saying that “often the origins of these events are near impossible to determine” and citing the still-unsolved mystery of the origins of Ebola virus.

But Richard Ebright, professor of chemical biology at Rutgers University, called the trip that concludes this week a “charade”, insisting it does not allow for “meaningful access” or “meaningful investigation”.

China’s government is desperate to convince the world that it is not to blame for the pandemic and thus absolve itself of responsibility for any of the subsequent devastation to the global economy. With some foreign politicians keen to lay the blame squarely on China, competing narratives have emerged.

Mike Pompeo, secretary of state under former President Donald Trump, advanced the unproven theory that the virus leaked from the Wuhan Institute of Virology (WIV) while Chinese officials endorsed the baseless claim that the pathogen came to Wuhan via a US military exercise. Chinese state media has also claimed that it may have arrived in imported frozen foods.

“When you deal with a world order where certain countries are big enough to create their own truths, you’re never going to get to a situation where there’s universally accepted truths,” said Tim Trevan, a former UN weapons inspector in Iraq and co-founder of Chrome Biosafety and Biosecurity Consulting. “China and America are already lining up to come to different conclusions.”

Behind this lies an intense scientific debate over whether the experiments done at labs such as the WIV yield benefits that outweigh the risks — and what kind of research governments should spend their money on in order to prevent the next pandemic.

That the WIV was experimenting on coronaviruses has stoked the “lab leak” theory that the virus escaped from the institute. Shi Zhengli, WIV’s leading expert on coronaviruses, has dismissed this by saying that the most Sars-Cov-2-like strain of the virus she studied at the lab was too genetically different from the current strain to be a recent predecessor.

Virologists’ leading theory is that predecessors of Sars-Cov-2 emerged in bats and evolved into a more dangerous strain — possibly within another animal intermediary. Daszak and Shi, who have worked closely together, warned in 2013 that such pathogens had the potential to infect humans.

They insist finding and analysing novel animal viruses was humanity’s best chance of preventing the next pandemic. So Daszak expressed dismay last year when the Trump administration halted a WIV project into bat coronaviruses, which had US National Institutes of Health funding.

David Robertson, head of bioinformatics at the Centre for Virus Research at the University of Glasgow, spoke for many when he asked: “How was the world so poorly prepared for this well-understood natural event — virus spillover of a Sars-like virus — when this had happened before and was predicted to happen again?”

It is accepted that capturing and lab reproducing pathogens from wild animals poses risks. The Obama administration ordered the NIH to stop funding such research in 2014 after a series of lab accidents, although it resumed doing so in 2017. “There’s a long history of accidental releases from even the most advanced and sophisticated labs in the world,” said Millett.

Some argue that China’s strict governance of research, and the system of hierarchy, are additional barriers to safety.

Trevan said it was “not defensible to say China should not have [high bio-risk] labs. They have amazing developments in biotechnology, they are a world leader in genomics.”

But, he added, planning and protocols alone do not prevent accidents. “You’ve got to become a learning organisation, not learning from the centre or top down. You’ve got to allow people to speak up and question everything,” he said. At the start of the pandemic, Beijing reiterated its strict regulations on what scientists could and could not say or research related to coronavirus.

In China, debate on the virus’ origins do not take place in public. Local media has barely covered the WHO trip while the team itself is cordoned off in a specially allocated 200-room wing of a hotel.

The location marker for the WIV disappeared from Baidu Maps in the weeks leading up to the WHO visit, despite remaining visible on competitor platform Gaode Maps. Baidu has refused to explain why.

“Most Wuhan people don’t care about the WHO trip,” said Evan Zou, a local who volunteered when coronavirus first hit the city. “We just want to get on with our lives.”

Additional reporting by Christian Shepherd in Beijing and Kiran Stacey in Washington DC