Covid-19 data points to animal origin but more studies needed to spot what and where: WHO advisers
- Sago report says research required to look at possibility of lab leak
- Information so far suggests the pathogen spread from animals to humans in a natural setting, it says
In their first report, the Scientific Advisory Group for the Origins of Novel Pathogens (Sago) said on Thursday that available epidemiological and sequencing data suggested Sars-CoV-2 spread from animals to humans in a natural setting.
The group of 27 scientists from around the world said the closest genetically related virus was a family of coronaviruses identified in horseshoe bats in China in 2013, which is 96.1 per cent close, and in Laos in 2020 with 96.8 per cent genetic overlap, but they were not close enough.
“These viruses do not appear to be sufficiently closely related to Sars-CoV-2 to be identified as the immediate source of acquisition,” the report said, adding that more studies need to be done to identify the original or intermediate host that spread it to humans.
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The Sago team was formed in October to advise the World Health Organization on the origins of emerging and re-emerging pathogens as the agency tries to restart the investigation into how the pandemic started.
In the latest Sago report, scientists said it was important to assess the possibility that Sars-CoV-2 was introduced to the human population through a breach in biosafety and biosecurity measures.
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Without naming the laboratory, the group said investigators would need access to and review the evidence of all laboratory activities with coronaviruses including Sars-CoV-2-related viruses or close ancestors, and the laboratory’s approach to implementation and improvement of laboratory biosafety and biosecurity.
The Wuhan Institute of Virology, located in Wuhan where researchers studied bat coronavirus and kept bat coronavirus RaTG13, a known close relative of Sars-CoV-2, has been the centre of the lab leak hypothesis.
The WHO mission last year visited the institute but did not carry out a thorough investigation.
“They recommend that all hypotheses remain on the table, and that further studies need to be done so that we can rule them out or in, but we can’t rule any of these hypotheses in or out without further information,” said Maria Van Kerkhove, head of the emerging diseases and zoonoses unit in the WHO’s health emergencies programme, who also co-led Sago.
“A lot of these pathogens are being worked on in labs around the world. There are many biosafety biosecurity procedures in place. But what this group will look at [is] was there a potential breach in some of these procedures which could potentially lead to infection in humans?”
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Three members of Sago – Vladimir Dedkov from Russia, Carlos Morel from Brazil and Yang Yungui from China – objected to including further studies into the laboratory incident in the report because there was “no new scientific evidence”.
The report said many studies would require further cooperation with China, including assessments of the 76,000 patients presenting to 233 health institutions in Wuhan in the months before the Covid-19 outbreak in December 2019.
China ruled out those patients as early Covid-19 cases but Sago said case definition was initially very stringent and many milder infections might have been missed.
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“There is relevant data outside China but access and cooperation from China is critical. Early case studies, sampling, interviews and other data-gathering is crucial,” said Filippa Lentzos, a biosecurity expert at King’s College London.
Tedros sent two letters to Chinese Premier Li Keqiang and Health Minister Ma Xiaowei in February, asking for information on the status of studies evaluating the laboratory hypotheses as well as its earliest investigations around suspected human cases in Wuhan.
Tredros also asked for the results of blood serum testing of 2019 samples and occupationally exposed workers from farms that supplied animal markets in Wuhan and Hubei province, but did not say whether China replied.
The report said Chinese scientists had presented unpublished data, including new unpublished serologic results of more than 40,000 stored samples from donors in Wuhan who gave blood between September and December 2019.
These samples were reported to have been tested for antibodies to Sars-CoV-2 and more than 200 samples proved positive initially, however, none were positive in a follow-up test. Other samples collected in Wuhan before December 2019 were reported to be negative on retrospective testing.
The group said it had requested further information on this data and the methods used to analyse these samples.
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They were also presented with unpublished animal studies in January, including a survey of raccoon dogs, susceptible to Sars-CoV-2 in two cities in Hebei province.
The studies did not find any positive match, nor did samples from 32,479 unknown animals from 18 provinces. Blood serum results from 1,211 livestock and poultry samples and 2,837 serum samples from dogs, cats, mink, foxes and raccoons also suggested no positive results for Sars-CoV-2 antibodies.
The WHO said that it was “just the start” and not a complete assessment and it did not guarantee finding the origin.
“Maybe one day we’re going to be lucky and we’re going to have the missing link. It took ages to trace HIV and when it entered the human population, and then we have to be patient, and we need a lot of tenacity,” said Jean-Claude Manuguerra, Sago vice-chairman.
