Scientists claim to have unearthed more clues about how the new coronavirus could have spread from bats through pangolins and into humans as the number of infections worldwide neared six million.
Writing in the journal Covid-19 Science Advances, researchers said that an examination of the closest relative of the virus found that it was circulating in bats but lacked the protein needed to bind to human cells.
The US-based scientists said this ability could have been acquired from a virus found in pangolins – a scaly mammal that is one of the most illegally trafficked animals on the planet.
Dr Elena Giorgi, one of the study’s lead authors, of Los Alamos national laboratory, said people had already looked at the pangolin link but scientists were still divided about their role in the evolution of Sars-Cov-2, the virus that causes Covid-19.
“In our study, we demonstrated that indeed Sars-Cov-2 has a rich evolutionary history that included a reshuffling of genetic material between bat and pangolin coronavirus before it acquired its ability to jump to humans,” she said, adding that “close proximity of animals of different species in a wet market setting may increase the potential for cross-species spillover infections”.
The study still doesn’t confirm the pangolin as the animal that passed the virus to humans, but it adds weight to previous studies that have suggested it may have been involved.
However, Prof Edward Holmes, an evolutionary biologist at the University of Sydney in Australia, said more work on the subject was needed. “There is a clear evolutionary gap between Sars-Cov-2 and its closest relatives found to date in bat and pangolins,” he said. “The only way this gap will be filled is through more wildlife sampling.”
The findings came as Donald Trump announced that the US was severing its ties with the World Health Organisation because it had “failed to reform”.
In a speech at the White House devoted mainly to attacking China for its alleged shortcomings in tackling the initial outbreak of coronavirus, Trump said: “We will be today terminating our relationship with the World Health Organization and redirecting those funds to other worldwide and deserving urgent global public health needs.”
The US is the biggest funder of the global health body, paying about $450m in membership dues and voluntary contributions for specific programmes.
It comes as deaths in the US climbed to more than 102,000 with 1,747,000 infections, by far the biggest total in the world.
It emerged on Friday that one person who attended the controversial mass pool parties in the Ozarks last weekend had tested positive for the virus. Authorities said they wanted to inform other people who were also at the gatherings of the risk.
There was another large spike in deaths in Brazil, where more than 27,000 people have died from the disease and which has the world’s second highest number of cases on 465,000.
There were also big surges in reported deaths in Russia and Iran on Friday. The former suffered its biggest daily increase in deaths – 232 in 24 hours – bringing the nationwide total to 4,374 while the latter identified more coronavirus cases in a day than in any time since early April; 2,819 more people tested positive on Friday.
Egypt registered 1,289 new cases and 34 deaths, the health ministry has said, marking another record of daily increases on both counts despite stricter curfew rules.
Other developments across the world include:
A leading UK government adviser has warned that it is too early to lift lockdown restrictions as planned next month because the number of new infections is still too high. John Edmunds, a professor of infectious disease modelling at the London School of Hygiene and Tropical Medicine, said he wanted the level of new cases to “driven down further” before larger gatherings are allowed as the government has said it wants to do. Tory MPs are still being bombarded by constituents with calls for Boris Johnson’s top adviser to quit after he appeared to breach lockdown rules.
Restrictions continue to be lifted to some degree across Europe, with thousands flocking to open-air cinemas to see films together for the first time in weeks.
In Australia, where states are expected to move to relax the rules to allow gatherings of more people from Monday, anti-vaccine protesters gathered in several cities to warn that they believed Covid-19 was a “scam”.
Also in Australia, scientists are examining the sewage waste in a town in Queensland where a 30-year-old man died this week from the virus. Nathan Turner is the youngest victim in the country so far and the case has baffled experts because he had not left the remote town of Blackwater.