File photo: IC

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 coronavirus tests, although the source of the infection is unknown. 

Local seafood markets remain closed and some subway services are suspended. 

Two confirmed cases and 12 asymptomatic cases were reported on Thursday among close contacts of a confirmed case. The confirmation of those patients broke Dalian's record of zero COVID-19 cases for 111 days. 

All the new cases were working in the same area at a local seafood processing company, according to an official report. 

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. 

To curb the spread of 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, said Luo Weixing, a government official.

The results of some nucleic acid tests were positive out of 1,318 samples collected from the environment and food at the warehouses and 18 branch stores of the seafood company, including areas such as toilets, the cafeteria and office buildings. 

As a large comprehensive enterprise, Dalian Kaiyang's business scope includes seafood processing, research and development, sales, bonded storage and imports and exports. The company has a storage capacity of more than 50,000 tons, including a public bonded warehouse of 30,000 tons designated by the  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 to track the source of the infection as soon as possible.

The city will send positive nucleic acid test samples to the national and provincial centers for disease control and prevention for gene sequencing, and they will make a comparison with known pathogenic genes to determine the source of the virus in Dalian.

The confirmation of a COVID-19 patient could deal a blow to the 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 - Liaoyu international seafood market - about 3.3 kilometers away from Dalian Kaiyang, were suspended on Wednesday afternoon, an office employee told the Global Times on Thursday. 

A vendor 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, Liaoyu seafood market has around 1,000 seafood stalls. 

Also on Thursday, China's State Council issued a guideline, demanding all imported meat products must be provided with a nucleic acid test certificate before coming into industrial plants for processing.

The guideline is intended to strengthen the regulations on imported food products due to the spread of COVID-19 in some countries.

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

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

Cold chain products and seafood once again came under the public 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, in early June.

"First Wuhan's Huanan 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 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.

Dalian shut down the Dalian Bay subway station on subway Line 3 on Wednesday, where the first confirmed patient travels every day between his home and his company. The local government said residents should not leave the city if not necessary. 

The infections caused Dalian to press pause button again when the city was on the track of business resumption and cinema expected to open for business.

Citywide recruitment activities, indoor gyms, swimming pools and culture centers as well as cinema are suspended from Thursday, officials said.