Coronavirus: China ramps up checks on food imports amid Beijing outbreak
- Customs authorities test thousands of products but all samples so far come back negative
- Virus found at the Xinfadi food market is much older than the one circulating in Europe, Chinese researchers say
China has stepped up inspections of imported food amid a coronavirus outbreak linked to a Beijing food market.
The decision comes as Chinese researchers trying to trace the source of the cluster said that the strain in the capital appeared to be related to but older than a variation circulating in Europe.
Song Yueqian, a quarantine official at the General Administration of Customs, said on Friday that the agency had launched a nationwide drive to inspect all cold-stored fresh products imported from “high-risk countries”.
He said authorities had so far tested more than 15,600 samples of imported food, include packaging, and all had come back negative for the virus.
Government agencies and food companies from more than three dozen countries had been asked to focus on preventing coronavirus contamination of food.
The measures were prompted by an outbreak linked to the Xinfadi food wholesale market, a centre in south Beijing that has been linked to most of the 183 cases of Covid-19 that have emerged in the city since June 11.
Researchers from the Chinese Centre for Disease Control and Prevention said they tested hundreds of samples taken from the market.
Mathematical modelling and analysis of mutations, or genome changes, indicated that the Beijing strain was earlier in the genetic evolutionary process.
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“Initial study of the genomic epidemiology showed the strain came from Europe, but differs from the strain that is currently prevalent in Europe. It’s older,” Zhang was quoted as saying in a statement on the website of the Communist Party’s anti-corruption watchdog, which has published a number of coronavirus updates.
Zhang said one explanation could be that the virus arrived in Beijing in contaminated imported frozen food and did not mutate during storage and transport.
Another possibility was that the virus was not eradicated through disinfection and was present at the market for some time without infecting anybody. When it finally did erupt, it had not mutated.
The assessment comes a day after China published the genome data of three samples – two from people and one from the environment – collected on June 11, when Beijing reported the first case of what grew to be a market cluster that would spread to neighbouring provinces within a week.
According to Nextstrain, an open-source project to analyse pathogen evolution and epidemic spread, the genomes are similar to sequences from many countries but with some differences.
It said the genome data indicated that the strain in the Beijing outbreak was part of an existing Sars-CoV-2 range and related to viruses circulating in Europe.
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“Additionally, we can see there is some diversity in these sequences – they are not identical. This may indicate unobserved circulation occurring before these samples were taken,” Nextstrain said.
It was not the result of a new jump from animals, it added.
The coronavirus is thought to have originated in bats before jumping to humans through an intermediate – but still unknown – host.
Researchers had suspected that the intermediary might have been a wild animal because of the early cases linked to the Huanan Seafood Wholesale Market in Wuhan, where the global pandemic started in December. Wild animals had been traded at the market.
But in Beijing, the coronavirus was found on a chopping board used to process salmon, raising public fears that fish were part of the infection chain.
Although seafood is known not to transmit the coronavirus, they can potentially be contaminated by people who are infected with Covid-19 and later passed on the virus.
The Chinese CDC is looking closely at the role of seafood stalls in the outbreaks, both in the Huanan and Xinfadi markets.
Wu Guizhen, Communist Party secretary of the National Institute for Viral Disease Control and Prevention, said researchers shifted their attention from wild animals because there was little probability of wild animal trade in Beijing. They also detected the coronavirus in a sample taken from the mouth of a salmon.
“We have been trying to find an animal intermediary when we tried to trace the origin of Sars-CoV-2 in the past, now maybe it’s high time we reviewed whether the virus comes from wild animals at all,” Wu said, referring to the official name of the virus.
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Liu Jun, assistant director of the institute, said environmental samples played an important role in determining how the outbreak started – positive samples in sealed products would confirm the possibility of virus transmitted through cold storage to the market.
Liu said that both the Xinfadi and Huanan markets were wet and poorly ventilated, good breeding conditions for the virus. However it did not mean the markets were the source of the outbreaks, he said.
The Chinese CDC said the data had also been shared with the World Health Organisation and the Global Influenza Data Initiative.