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The Xinfadi market covers 112 hectares in Beijing’s Fengtai district. Photo: AFP

Beijing Covid-19 outbreak puts food markets back in infection focus

  • The coronavirus that causes the disease can survive for weeks in the wet and cool conditions at such sites
  • But there are differences between the cluster in the capital and the one in Wuhan more than six months ago
The unexpected coronavirus outbreak linked to Beijing’s Xinfadi food market raises renewed questions about hygiene and safety in such places, with disease experts saying they are ideal environments for virus transmission.
China’s capital, which has a population of 21 million, was in “wartime” contingency mode to contain the outbreak, with mass testing and contact tracing under way.
Health authorities said 27 cases were reported on Monday, bringing the total number of infections in the city since Thursday to 106, with five of those in provinces outside Beijing. The city had previously gone 55 days without a locally transmitted case.

Comparisons are being drawn with the original outbreak in the city of Wuhan in central China six months ago, in which a cluster of patients was linked to the Huanan Seafood Wholesale Market in that city.

Malik Peiris, a virology professor at the University of Hong Kong, said the coronavirus that caused the pneumonia-like symptoms of Covid-19 could survive for weeks in the wet and low-temperature conditions found in the markets.

Water sprayed for cleaning can form aerosols of bacteria and pathogens from surfaces, which combined with heavy foot traffic of shoppers and workers, can help the virus spread.

“It’s an ideal environment, to allow the virus to transmit effectively and efficiently,” Peiris said.

00:47

WHO downplays 'hypothesis' linking salmon to Beijing’s latest coronavirus outbreak

WHO downplays 'hypothesis' linking salmon to Beijing’s latest coronavirus outbreak

Dubbed the “vegetable basket of Beijing”, Xinfadi is Asia’s biggest wholesale food market, occupying 112 hectares (277 acres) in the city’s southwestern Fengtai district. It has more than 2,000 stalls selling everything from meat and seafood to fruit and vegetables. The market handles in excess of 3,000 pigs and 1,500 tonnes of seafood a day, according to its website.

As many as 15,000 people visit the market each day and 3,000 trucks make daily deliveries, according to the Beijing municipal government. The market has been shut for medical testing and investigation.

The Xinfadi and Huanan markets do have similarities. They both sell a wide range of foodstuffs, including meat and seafood, and are near transport hubs. The Xinfadi long-distance bus station is next to the market, while the Huanan market is two blocks from Wuhan’s Hankou railway station.

However, the Huanan market is much smaller than Xinfadi, with an area of 5 hectares and around 1,000 stores.

The Beijing Centre for Diseases Prevention and Control said traces of the coronavirus were found on a cutting board used to process imported salmon at the market. Experts said the fish were not the source of infection but could have been contaminated.

An editorial published in Asian Fisheries Science journal in April by scientists from the United Nations, and a dozen countries, including China and the United States, said Sars-CoV-2, the official name for the virus that causes Covid-19, was a type of betacoronavirus that only infected mammals. There was no evidence to suggest the virus could infect fish or most other marine animals, it said.

However, like any other surface, seafood could become contaminated with Sars-CoV-2, especially when handled by people who were infected with the virus, the editorial said.

Peiris said the coronavirus was not from fish, but the packaging could become contaminated.

“The fish themselves are not likely to be infected. But there’s packing and whatnot that can get contaminated with the virus,” he said.

Benjamin Cowling, a professor of epidemiology at the University of Hong Kong, said it was possible but unlikely that frozen imported fish was the source.

“I think a more likely source is an unrecognised infection that occurred in a person from another part of the country travelling to Beijing and infection was then able to spread in Beijing,” Cowling said.

“The more than 50 cases that have now been identified following mass testing show how easy it is for mild or asymptomatic infections to go unrecognised.”

While the food markets had conditions conducive to an outbreak, the cluster of infections at the Beijing and Wuhan markets could be coincidence, the researchers said.

“It’s kind of a coincidence but I think it is likely a scenario of efficient virus transmission,” Peiris said.

Cowling said there have been many clusters in various types of locations, but only a few in markets.

02:17

Beijing district in ‘wartime emergency mode’ after spike in local Covid-19 cases

Beijing district in ‘wartime emergency mode’ after spike in local Covid-19 cases

Zhang Wenhong, an infectious disease expert at Shanghai’s Huashan Hospital, said there were similarities between the Beijing and Wuhan food market clusters, according to news outlet Caixin. Both outbreaks happened in crowded and inadequately ventilated sites. The main difference was that the first infection in the Beijing cluster got sick at the start of this month and was diagnosed within one week. All subsequent cases in this cluster were linked to the Xinfadi market and immediate action was taken, Zhang said.

In Wuhan, health authorities announced on January 20 there was human-to-human transmission, nearly two months after the first case had appeared, he said.

Because a lot of people and traffic moved through Xinfadi, it is possible new hotspots could appear elsewhere, according to Zhang.

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