A scientist at the forefront of an international effort to track the deadly coronavirus outbreak has shot down claims about the disease’s origins, including that it escaped from a Wuhan laboratory after being genetically engineered.
Trevor Bedford, of the Fred Hutchinson Cancer Research Center in Seattle, rubbished stories circulating on social media that Covid-19 was created at Wuhan Institute of Virology or elsewhere in China, rumours that prompted the World Health Organization to warn of an “infodemic” of false news on the outbreak.
“There is no evidence whatsoever of genetic engineering that we can find,” he said at the American Association for the Advancement of Science meeting in Seattle. “The evidence we have is that the mutations [in the virus] are completely consistent with natural evolution.”
One source of rumours was a paper posted by scientists in India claiming that short insertions in the viral genome had an “uncanny similarity” to HIV. Although the paper was quickly withdrawn, its allegations live on in social media.
The research was “wrong on many levels,” said Dr Bedford, whose lab studies the evolution of viruses. The genes it shares with HIV are extremely short sequences naturally shared by other organisms and “repeated again and again throughout the tree of life.”
He also disputed claims that Covid-19 might have infected humans from snakes or even fish. The most likely scenario, based on genetic analysis, was that the virus was transmitted by a bat to another mammal between 20-70 years ago. This intermediary animal — not yet identified — passed it on to its first human host in the city of Wuhan in late November or early December 2019.
Dr Bedford is a leader of the worldwide Nextstrain collaboration that began to analyse Covid-19 genomes when they were released in January by Fudan University and the Chinese Centre for Disease Control. By now scientists around the world have published the genetic sequence of virus taken from about 100 patients.
They show mutations taking place at a slow pace as the infection passes from person to person. Typically the virus in one patient today is different in around five of the 30,000 biochemical letters of its genetic code, but these are random changes rather than any sign that it is becoming more virulent or infectious, Dr Bedford said.
By comparing virus taken from different patients and knowing its mutation rate, he and his colleagues can also estimate the total number of cases so far. He said the result was similar to that produced by more conventional epidemiology.
“We get upwards of 200,000 total infections, which fits with the estimates already published by Neil Ferguson and colleagues at Imperial College London,” Dr Bedford said. But he was reluctant to forecast the future course of the epidemic.
The death toll from the virus was on Friday approaching 1,500 with more than 64,000 case identified, according to Chinese state media. But medical experts and frontline health workers in China have warned that Beijing is under-reporting the severity of the outbreak.