For over three years scientists have been looking for an animal that could 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 that additional evolutionary steps must have taken place in another animal to make them infectious to humans.
Now that step may no longer be necessary. On Thursday Professor George Gao, former head of the China Center for Disease Control, said the science needed to be “rethought” because it now appeared that a further step was unnecessary. The virus may have jumped directly from bats to humans.
Professor Gao told a conference in Geneva that scientists were also questioning whether Sars and Mers had jumped directly into humans, without necessarily the palm civets or camels that were initially blamed for the spill.
Why is this important? 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 that they were being brought from outside to be sold in local wet markets.
Investigating bat coronaviruses
But bats were coming into Wuhan through another route. Scientists from the Wuhan Institute of Virology (WIV) were collecting the animals in China and southeast Asia and bringing them to the city for “sequencing, archiving, analysis and manipulation”.
Their goal was to investigate bat coronaviruses that could evolve to infect humans.
Wuhan researchers have collected more than 220 Sars-related coronaviruses, at least 100 of which belong to the same beta-coronavirus subgenus to which Covid-19 belongs, which has never been published. Many of them came from caves in Yunnan province, about 1,000 miles from Wuhan.
King’s College London has described such fieldwork to collect potential pandemic viruses as “extremely high risks” and researchers often work in limited light with exposed skin.
Handling bat bites and scratches carries the risk of creating an entry wound for viruses and collecting blood or urine risks creating an infectious aerosol.
A recent US Senate report on the origins of the pandemic described the Wuhan researchers as having a “nonchalant” approach to safety.
Staff were seen not wearing adequate protective equipment. In 2017, Wuhan researcher Tian Junhua told the Wuhan Evening News that he once forgot his PPE and was splattered with bat urine requiring self-isolation for two weeks.
Several researchers were videotaped collecting samples without masks or gloves.
Once back in the lab, graduate students often processed samples in inadequate biosafety levels.
The US Senate committee concluded in its report published this week: “WIV researcher may have been infected with Sars-CoV-2 during field activities.
Rapid spread in Wuhan
“In this case, an infected researcher could act as a common and persistent source of infection leading to the outbreak of Covid-19 in Wuhan.
“This case is consistent with the early epidemiology that shows the rapid spread of the virus in different areas of Wuhan.”
If no other species is now needed for an outbreak, it raises the possibility that the virus was brought back to Wuhan by an infected lab worker, or leaked directly from the lab.
It’s also possible that an infected civilian came with a bat and then made the trip to Wuhan, but it’s less likely that others wouldn’t have been infected along the way.
The debate about the origins of Covid has largely focused on whether it was a laboratory leak or whether it was transmitted from animal to human. Now it seems that it may be reasonable together.