It’s a danger to the world that the precise origins of Covid-19 remain a mystery

If there was a smoking gun in the wet markets of Wuhan we should know by now, and the lack of urgency by China in stamping out the wildlife trade suggests they don’t think the answer lies there either

It is almost exactly two years since the pandemic began. According to an official document seen by the South China Morning Post, the first retrospectively diagnosed case of Covid in Wuhan was on Nov 17 2019, while genetic analysis points to a similar date, Nov 18. (The so-called “patient zero” discussed in the media this week has been known about for months and is very unlikely to be the first case, even according to the World Health Organisation.)

In the case of Sars, 19 years ago, and Mers, nine years ago, the first known cases were followed within a couple of months by unambiguous clues as to how the virus jumped from an animal source into people. Both viruses live naturally in bats, which had somehow infected intermediate animal hosts such as palm civets and camels before transmitting to people.

Yet in the case of Sars-CoV-2, despite the fact that genetic testing technologies have advanced by leaps and bounds, we have no clear pattern of early cases stemming from an animal source. Dr Michael Worobey’s analysis this week, pointing to a patient with symptom onset on Dec 11 who was a seafood vendor in the market, is consistent with the Chinese authorities’ conclusion in May 2020 that the market was the site of a superspreader event, not the source. The positive samples from surfaces in the market show no correlation with the sale of wildlife products.

Meanwhile, there are still no cases of an original animal host found to be carrying this virus. Closely related viruses have been found in bats, and in three smuggled pangolins, but none is close enough to be a direct progenitor of the pandemic. This is despite the testing of 80,000 animals in China and close to 2,000 animals from the wildlife trade between 2017 and 2021. The trail has gone cold.

That’s odd. If there was a smoking gun in the wet markets of Wuhan we should know by now, and the lack of urgency shown by the Chinese authorities in stamping out the wildlife trade (plus their decision in September to blame a laboratory in North Carolina) suggests that they don’t think the answer lies in the wildlife trade either.

Having just published a book on this mystery, with Alina Chan, I am surprised by how many people ask me why it matters, given that an admission from Beijing is unlikely. Some even argue that it would be better if we do not find out how it started, in case the truth leads to a row with China.

Finding the origin of Covid matters because the virus has now probably killed an estimated 16million people, and we owe it to them and their families to investigate. It matters because bad actors – terrorists and rogue states – are watching the episode and wondering what they can get away with in terms of bioterrorism or pathogen research. And it matters because we need to know how to prevent the next pandemic.

If this pandemic began with the food trade, changes must be made there to prevent another. If it began with products used in traditional Chinese medicine, a set of practices endorsed by the World Health Organisation in 2019 at the urging of Xi Jinping, that needs revisiting. And if the pandemic began as a result of risky virology research, that category of work needs to be made safer. Wuhan is the site of the world’s most active research programme on Sars-like viruses, and viruses have escaped from labs many times.

Here is a description of one of the experiments carried out in Wuhan a few years ago. Samples taken from bats in a cave in Yunnan were analysed for viruses closely related to Sars. One of the viruses was used to infect human cells in the lab at biosecurity level 2 (meaning that sometimes the only protection was gloves, basically). It was engineered to carry the spike gene of each of various other Sars-like viruses that had been collected – with the aim of finding out how capable those other viruses were of infecting human cells.

The engineered viruses were then used to infect “humanised” mice – which had the human ACE2 viral entry receptor gene. In some cases they produced viral loads several orders of magnitude greater than the original natural virus in the lungs and brains of the humanised mice, sometimes killing more of the animals.

At the very least, such experiments failed in their ostensible purpose: to predict the next pandemic. At worst, they may have caused it. Yet the US government money going into such work continues to flow in the millions.

Until we can rule out a laboratory origin for Covid, we must act as if it may have happened. The world needs to come together with a pandemic treaty, agreeing to limit this risky pathogen research, agreeing to transparent sharing of data during a pandemic and agreeing to sanction those countries that refuse to sign up to such a treaty.