The mystery still envelops the origin of Covid-19

© NOEL CELIS
The first cases of the virus were linked to a market in Wuhan, but they could have originated elsewhere

As many scientists rush to find vaccines to tame the spread of the coronavirus pandemic, other researchers are probing the past, trying to unravel one of the virus’s biggest mysteries: exactly where it came from.

The World Health Organization has assembled an international team of 10 scientists to trace the origins of the virus.

They will need to investigate both the suspect animals and how the first patients may have been infected.

“We want to know the origin and we will do everything to know the origin,” WHO chief Tedros Adhanom Ghebreyesus told reporters on Monday.

But success is by no means guaranteed.

– Source of the spread –

The first cases were reported in the Chinese city of Wuhan a year ago, before countries around the world started recording increasing infections.

The WHO said the first cases in Wuhan would date from early December.

But “where an epidemic is first detected does not necessarily reflect its origin,” he added in a November report.

In recent months, researchers in various countries have suggested that cases may have gone unnoticed long before December 2019, based on analysis of sewage or blood samples.

But there is a lack of “clear evidence” to back up these claims, said Etienne Simon-Lorière, of the department of virology at the Institut Pasteur in Paris.

To establish a family tree of viruses, researchers rely on genetic analysis.

This may help “to better understand the dynamics of transmission, in particular how the virus may have evolved over time and how clusters might be related in time and place,” the WHO said.

– Jump towards humans –

Scientists agree that the disease is of animal origin.

“The big question is what made him jump into humans,” Etienne Simon-Lorière told AFP.

Suspicion has fallen on bats, which are “a major reservoir for coronaviruses”, he adds.

But there probably would have been an intermediary animal to bring SARS-CoV-2 back to humans.

The pangolin – a mammal subject to regional wildlife smuggling – was identified as a likely vector early on on the basis of genetic analysis. But the matter is not settled.

WHO investigators will need to clarify this point by surveying the Wuhan wet market, which sold live and wild animals and has been linked to many early cases.

The team will be armed with clues we didn’t have at the start of the pandemic.

Simon-Loriere said they could search for an animal with a virus receptor, a protein called ACE2, similar to that found in humans.

It is through this receptor that the virus attaches itself to cells.

Some animals like mink and ferrets have a very similar receptor to humans, while others are quite different.

Another original theory that swirled in conspiracy rumors for months was that the Wuhan Institute of Virology was involved in the outbreak.

Amid diplomatic tensions, US President Donald Trump touted the idea, saying the virus could have escaped the biosafety lab.

China has dismissed the charges.

While Simon-Loriere said it was not yet possible to completely rule out the idea that the virus had accidentally escaped, he stressed that there was “no indication that it was human origin “.

“All the elements of its genome have already been observed in nature, mainly in bat coronaviruses,” he said.

– Unravel the riddle –

The WHO says understanding how an epidemic started is “essential to prevent further introductions into the human population”.

But he warned that the process of tracing how disease jumped from animals “is an enigma that can take years to resolve.”

“The introduction of a new virus into the human population is one of the biggest mysteries an epidemiologist can hope to unravel,” he said.

The aim is to “understand the mechanism and put in place measures to prevent the emergence of a new SARS-CoV-3, 4, etc.”, said Simon-Lorière.

For example, during the SARS epidemic of 2002, the ban on the consumption of civets – identified as an intermediate host of this coronavirus – would have helped to prevent the reintroduction of the virus into humans.

The United Nations health agency sent a preliminary team to Beijing in July to lay the groundwork for the investigation.

But it’s still unclear when the bigger team will be able to travel to China to start work.

At the end of November, the WHO said it hoped to have a larger team of scientists in the field “as soon as possible”.

The United States has accused Beijing of not being transparent, as it says the WHO bowed to China and dragged its feet to investigate the start of the epidemic.

Others have expressed concern that the agency has allowed China to dictate terms for an international investigation into the origins of the virus.

Tedros told critics to stop “politicizing” the issue on Monday.

pr-klm / pg / dd