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Coronavirus pandemic
ChinaPeople & Culture

Coronavirus case in northern China reveals mystery of carrier who tests negative and has no symptoms

  • Tianjin kitchen worker tested positive to Sars-CoV-2 but close contacts, workplace and even food in kitchen held no clues to source of infection
  • CDC retested workers and found chef returned negative nucleic acid test but positive serological result

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A new coronavirus infection in Tianjin – the first in 110 days – was a mystery since the patient had not left Tianjin in at least two weeks. Photo: Xinhua
Zhuang Pinghui
The first local Covid-19 cases in northern Tianjin city in 110 days were infected by an asymptomatic carrier who was believed to have contracted the illness in neighbouring Beijing, a Tianjin CDC official said.
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“The conclusion is correct and scientific. The most likely method of transmission was human to human but the investigation is continuing in order to find the source of infection and to rule out other possible ways of infection,” Zhang Ying, deputy director of the Tianjin Centre for Disease Control and Prevention, told reporters on Monday morning.

The finding highlights the complex and difficult task China faces in trying to avoid a possible second wave of Covid-19 caused by asymptomatic infections or imported cases.

Cities with severe Covid-19 infections, such as Wuhan where the global pandemic started and Shulan in northeastern Jiliin province, have imposed citywide nucleic acid tests.

Beijing, where 236 people were diagnosed with Covid-19 between June 11 and June 21 – mostly related to the Xinfadi Food Wholesale Market – is also putting in place gradual citywide testing to identify infections in the community.

In Tianjin, mystery surrounds how a 22-year-old hotel kitchen worker became infected. He was diagnosed with Covid-19 last Wednesday but had no history of travel two weeks before being testing positive. All close contacts of the man took nucleic acid tests and were found to be negative.

The man washed dishes and occasionally cleaned frozen seafood for his work. The centre tested samples of beef, lamb, salmon, vegetables and fruit. They were found to be negative and so were environment samples from the workplace.

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