Hard to prove if Covid virus originated from frozen food: WHO team member

While the WHO team that visited China to begin its search for the origin of SARS-CoV-2 said frozen food is one of the likely sources of the virus, one of the team members, Prof Dominic Dwyer, said it was “hard to prove” if that was indeed the case.“Contamination from frozen food is possible when the pandemic is already happening, and such food is shipped from places with active cases. There is evidence that frozen foods can cause an outbreak (like in the Xinfadi market in Beijing last June), where the foods coming in to the market are contaminated by material from people with COVID-19 somewhere in the world. However, it is much harder to show that frozen foods could cause the beginning of the outbreak in late 2019, hence the term ‘possible’. This is clearly an area that needs more research, and this has been recommended by the WHO team,” Dwyer, from the New South Wales Health Pathology organisation whose primary research area is understanding how outbreaks occur, told TOI. “It was difficult to ascertain whether frozen foods were kept in the market, let alone wildlife — as wildlife trade is illegal in China.”The frozen food theory, which Chinese state media had rallied behind, had implied that the virus may have originated outside China. When WHO mission head Peter Ben Embarek said it was a possibility, the discussion it generated was one filled with scepticism. Then, last week, WHO director general Tedros Adhanom Ghebreyesus said that all theories “remain open”. What the WHO remains firm on is that the virus did not originate in a lab. “Outbreaks can occur in labs and there have been a number of these all over the world. It is uncommon but it does occur. The Wuhan Institute of Virology is a very impressive and modern facility with an extremely good high-level biosecurity lab,” Dwyer said. “Just because they work on viruses does not mean they have live viruses there. For example, the closest relative of SARS-CoV-2 has actually never been grown there. You really need to culture the virus in order to have an accident. Also, understanding the sort of viruses they worked with and research they did was helpful but, of course, we could only go on what they told us.”Dwyer was one of 14 scientists who visited China over 12 days to try and map how Covid-19 broke out. They visited the two hospitals which took in the first few cases, a Covid-19-affected community, the Wuhan Institute of Virology, public health labs, the Huanan frozen food market and an agricultural university. “When the cases started emerging, there was, of course, no Covid-19-specific system in place in China to track the impact. They were focusing on people who visited hospitals in December, after which a pattern started emerging … The system for surveying diseases in China did not pick up what was going on as the system was not designed to pick up a disease like Covid-19,” Dwyer said. The team found that of the 174 cases initially recorded, only half had passed through the Huanan market. “That market is closed now. But when you walk through it, you get a clear sense of space — it was a market that (the virus) was easy to explode in. It’s very crowded, lots of little stalls, poor ventilation, poor drainage, easily 10,000 people visiting a day.”Embarek had in Wuhan said the findings do not “dramatically change” what is known of the outbreak so far. Dwyer said the process to trace the origins will, of necessity, be carefully worked out: “It was a success from the point of view that WHO was able to secure a lot of data China had previously refused to give them. We were there to find the origins and that remained inconclusive. It would have been naïve to think we could find the origins in 12 days.” He added, “From the point of view of the epidemic exploding, it all happened in China. There is no doubt about that. Wuhan was the epicentre of virus movement in humans. The difficult part is the bit before that. Did the virus actually originate in Wuhan or somewhere else? We think the virus came from bats and some intermediate animals like pangolins, and where they were originally is hard to determine.”As for transparency, he said China "cooperated well and gave us all the information we asked for." However, he added, “We could only go on what we were told. Was there more data available? We don’t know at this stage.”What could be done next in China, he added, are a “serosurvey for SARS-CoV-2 antibodies in blood donations from 2019 through the Wuhan Blood Centre, expansion of an integrated molecular, clinical and epidemiological database to cover all global information relevant SARS-CoV-2 origin studies, studies to examine the ability of SARS-CoV-2 to survive the food cold chain and freeze-thaw cycles and trace-backs of farms that raised domesticated wildlife and meat for the Huanan and other markets.”