The confirmation that COVID-19 was spread among employees working at a seafood processing company in the coastal city of Dalian in Northeast China's Liaoning Province has had a domino effect on the city, with more than 190,000 residents preparing to receive COVID-19 tests, while the local seafood markets remain closed, and some subway services suspended; however, the source of infection remains unknown.

(File photo: CFP)

Two confirmed cases and 12 asymptomatic cases were reported on Thursday among close contacts of a COVID-19 confirmed case. All new cases were working in the same workshop at a local seafood processing company, according to an official report at a press conference. 

Vendors and residents reached by the Global Times said infected workers may be employees from the Dalian Kaiyang seafood company, located in the Dalian Bay area. 

In the wake of a rising number of COVID-19 infections, the city will provide COVID-19 tests to more than 190,000 people around the city, including 130,000 in the Dalian Bay area, and another 30,000 from two local communities, as well as people in regions that might have been exposed to the coronavirus, Luo Weixing, a government official said.

All people, products, packaging and environment at the warehouses and 18 branch stores of the seafood company were tested, with all the nucleic acid test results returning negative.  

Dalian Kaiyang is a large-scale comprehensive enterprise integrating seafood processing, research and development, sales, bonded storage, import and export trade. The company has a storage capacity of more than 50,000 tons, including a public bonded warehouse of 30,000 tons designated by the national customs authority. 

The company has suspended its operations and all employees are under medical observation, a government official revealed at the press conference. Dalian authorities said they had acquired detailed information related to their imported products and trading channels, and they will begin  tracking the source of the infection as soon as possible 

The confirmation of a COVID-19 patient could deal a blow to seafood industry in Dalian, a coastal city that relies heavily on the seafood business, even though authorities did not reveal whether the man contracted the virus through seafood or cold-chain products.

Operations at one of the biggest local seafood markets - the Liaoyu international seafood market - about 3.3 kilometers away from the Dalian Kaiyang, were suspended on Wednesday afternoon in the wake of the confirmed cases, an office employee told the Global Times on Thursday. 

A vendor at the seafood market confirmed with the Global Times that shops in the market were closed on Wednesday and all vendors were given COVID-19 tests. Taking up an area of about 12,000 square meters, the Liaoyu seafood market is home to about 1,000 seafood stalls. 

The novel coronavirus has been detected in local imported seafood samples. On July 3, Dalian customs detected novel coronavirus on the inner wall of a white shrimp container and three outer packaging samples of frozen white shrimp imported from Ecuador. 

Customs authorities have carried out COVID-19 surveillance on cold chain food from overseas nations to prevent the spread of COVID-19 through imported cold chain food. 

Cold-chain products and seafood have once again come under the public's spotlight after the coronavirus was found on a chopping board that was used to cut salmon at Xinfadi market, a large wholesale food market in Beijing.

"First Wuhan's Hunan seafood market; then the Xinfadi wholesale market in Beijing and now the patient working at seafood company, it reminds us of the risks associated with cold chain products and how easily they can spread COVID-19," Wang Guangfa, a leading Chinese respiratory expert at Peking University First Hospital in Beijing and member of the national medical expert team dispatched to Wuhan in early January, told the Global Times on Thursday.

The original source of the COVID-19 infection may have involved multiple channels, Wang said, noting that finding infections in many meat processing companies in foreign countries, such as the US and Romania, further backups the theory.

In order to curb the spread, Dalian on Wednesday shut down the Dalian Bay subway station on subway Line 3, where the confirmed patient travels every day between his home and his company. Citywide recruitment activities will also be suspended from Thursday.