Covid 19 origins: Why a lab leak just became more likely

Residents in Wuhan line up to be tested for Covid-19. Photo / AP

Bats were coming into Wuhan through a route that did not involve wet markets, professor tells conference.

For more than three years scientists have been looking for an animal that could have spread Covid-19 to humans.

The closest coronaviruses to Covid-19 in nature are found in Chinese bats, but their DNA is different enough to suggest there must have been extra evolutionary steps in another animal to make them infectious to humans.

Now that step may no longer be necessary. On Thursday Professor George Gao, the former head of the Chinese Centre for Disease Control, said that science needed a “rethink” because it now seemed an extra stage was not needed. The virus may have jumped straight from bats to humans.

Prof Gao told a conference in Geneva that scientists were also questioning whether Sars and Mers had jumped directly into humans, without needing the palm civets or camels originally blamed for the spillover.

Why does this matter? It is important because bats are not native to Wuhan, where the virus first emerged. They do not live in the area, and there is no evidence they were being brought from outside for sale in local wet markets.

Investigating bat coronaviruses

Yet bats were coming into Wuhan through another route. Scientists from the Wuhan Institute of Virology (WIV) were collecting the animals in China and south-east Asia and bringing them to the city for “sequencing, archiving, analysis and manipulation”.

Their goal was to investigate bat coronaviruses that might evolve to infect humans.

Wuhan researchers had collected more than 220 Sars-related coronaviruses, at least 100 belonging to the same beta-coronavirus subgenus to which Covid-19 belongs, which have never been made public. Many were from caves in Yunnan Province, some 1600km from Wuhan.

King’s College London has described such fieldwork to collect potential pandemic viruses as posing “really, really high risks”, with researchers often working with limited light with exposed skin.

Handling bats risks bites and scratches that can create an entry wound for viruses while collecting blood or urine risks creating infectious aerosols.

The recent US Senate report into the origins of the pandemic described Wuhan researchers as having a “nonchalant” approach to safety.

Staff were seen without wearing adequate protective equipment. In 2017, Wuhan researcher Tian Junhua told the that he once forgot his PPE and was splattered with bat urine, which required self-isolation for two weeks.

Some researchers were videoed collecting samples without masks or gloves.

Once back in the lab, samples were often processed by graduate students amid inadequate biosafety levels.

The US Senate committee concluded in its report published this week: “A WIV researcher could have been infected with Sars-CoV-2 during field expedition activities.”

Rapid spread in Wuhan

The researcher continued: “Under this scenario, an infected researcher could serve as a continuous common source of infection leading to the Covid-19 outbreak in Wuhan.

“This scenario is consistent with the early epidemiology showing rapid spread of the virus in multiple areas of Wuhan.”

If no other species is now needed for an outbreak, it increases the possibility the virus was brought back to Wuhan via an infected lab worker, or that it leaked directly from the lab.

It is also possible that a civilian became infected with a bat and then made the journey to Wuhan, but it is less likely that others would not have been infected along the way.

The debate about the origins of Covid has centred largely on whether it was a lab leak or transmitted from animal to human. Now it appears it could reasonably be both together.