At the Guardian Dominic Dwyer, a member of the WHO task force that wen to China to investigate the source of SARS-CoV-2, explains the task force’s conclusions:
This is what we learned about the origins of SARS-CoV-2.
Animal origins, but not necessarily at the Wuhan markets
It was in Wuhan, in central China, that the virus, now called Sars-CoV-2, emerged in December 2019, unleashing the greatest infectious disease outbreak since the 1918-19 influenza pandemic.
Our investigations concluded the virus was most likely of animal origin. It probably crossed over to humans from bats, via an as-yet-unknown intermediary animal, at an unknown location. Such “zoonotic” diseases have triggered pandemics before. But we are still working to confirm the exact chain of events that led to the current pandemic. Sampling of bats in Hubei province and wildlife across China has revealed no Sars-CoV-2 to date.
We visited the now-closed Wuhan wet market which, in the early days of the pandemic, was blamed as the source of the virus. Some stalls at the market sold “domesticated” wildlife products. These are animals raised for food, such as bamboo rats, civets and ferret badgers. There is also evidence some domesticated wildlife may be susceptible to Sars-CoV-2. However, none of the animal products sampled after the market’s closure tested positive for Sars-CoV-2.
After Covid-19, China brought in new regulations for the trade and consumption of wild animals.
We also know not all of those first 174 early Covid-19 cases visited the market, including the man who was diagnosed in December 2019 with the earliest onset date.
However, when we visited the closed market, it’s easy to see how an infection might have spread there. When it was open, there would have been about 10,000 people visiting a day, in close proximity, with poor ventilation and drainage.
There’s also genetic evidence generated during the mission for a transmission cluster there as viral sequences from several of the market cases were identical. However, there was some diversity in other viral sequences, implying other unknown or unsampled chains of transmission.
A summary of modelling studies of the time to the most recent common ancestor of Sars-CoV-2 sequences estimated the start of the pandemic between mid-November and early December. There are also publications suggesting Sars-CoV-2 circulation in various countries earlier than the first case in Wuhan, although these require confirmation.
The market in Wuhan, in the end, was more of an amplifying event rather than necessarily a true ground zero. So we need to look elsewhere for the viral origins.
Then there was the “cold chain” hypothesis. This is the idea the virus might have originated from elsewhere via the farming, catching, processing, transporting, refrigeration or freezing of food. Was that food ice-cream, fish, wildlife meat? We don’t know. It’s unproven that this triggered the origin of the virus itself. But to what extent did it contribute to its spread? Again, we don’t know.
Several “cold chain” products present in the Wuhan market were not tested for the virus. Environmental sampling in the market showed viral surface contamination. This may indicate the introduction of Sars-CoV-2 through infected people, or contaminated animal products and “cold chain” products. Investigation of “cold chain” products and virus survival at low temperatures is still under way.
The most politically sensitive option we looked at was the virus escaping from a laboratory. We concluded this was extremely unlikely.
We visited the Wuhan Institute of Virology, which is an impressive research facility, and looks to be run well, with due regard to staff health.
Chinese policy makers have been floating an implausible theory: The novel coronavirus didn’t originate in China but was imported from Europe. That’s what a former chief epidemiologist of the Chinese Center for Disease Control and Prevention told an academic conference last fall. One theory is the virus rode into Wuhan on frozen-food packaging.
This month the World Health Organization visited China to investigate the origins of the virus. A member of the WHO delegation said it’s “possible that a frozen carcass could have been shipped” to China and introduced the virus, giving some validation to the food-packaging idea. Reporting has suggested that China required the WHO to agree it would investigate the food hypothesis as a condition of entering Wuhan. By lending credence to this improbable theory, WHO is damaging trust in the important project of figuring out where the virus originated.
The most common culprit cited by Chinese officials is frozen salmon, though officials have also suggested the virus may have hitched a ride on frozen cod, pig heads or other products. In response, Beijing has suspended imports of some food products and introduced inspections and tests of frozen food, which has frequently held up imports from the U.S. and Europe.
The U.S. Food and Drug Administration weighed in last week with a forceful statement. “There is no credible evidence of food or food packaging associated with or as a likely source of viral transmission,” the Acting Commissioner Janet Woodcock said in a Covid update on Thursday.
Other scientific bodies have reached similar conclusions. The International Commission on Microbiological Specifications for Foods has stated: “Despite the billions of meals and food packages handled since the beginning of the COVID-19 pandemic, to date there has not been any evidence that food, food packaging or food handling is a source or important transmission route.” More than 100 million cases of Covid have been diagnosed world-wide and, outside China, not a single case has been traced to food or food packaging.
It seems to me that it would help the task force’s case substantially if they could document a single case of the transmission of SARS-CoV-2 via frozen food.
All I can say is that it seems like an extraordinary way of conducting an investigation to me. Is evidence no longer necessary? If the standard of proof is the absence of contradicting evidence, it would seem to me that broadens the possibilities enormously. It could have been transported via a meteor strike. Planted by alien invaders. Carried on the shoe of a visitor. The possibilities are endless.