Dealers at the Xinfadi market have their information registered on Friday. Beijing authorities shut down the market after new COVID-19 cases linked the market. Photo: Li Hao/GT
The genome sequencing of the virus sample from a mysterious COVID-19 patient reported in North China's Tianjin is the same as that from the clustered infections in Beijing's Xinfadi market, dispelling public fears over the unknown source of infection.
Based on the epidemiological history and genome sequencing results, the case is a human-to-human transmission, according to the Tianjin Centers for Disease Control and Prevention (Tianjin CDC) on Monday.
Xinfadi market is where the latest outbreak was detected in the capital city, Beijing.
The patient, a 22-year-old man working at Tianjin's Conrad hotel, was confirmed to be infected with COVID-19 on June 17.
Zhang Ying, deputy head of the Tianjin CDC, said on Monday that a preliminary investigation showed the confirmed patient contracted the virus from a chef who also works in the Conrad hotel and the chef tested IgM positive. People who test IgM positive have gained viral antibodies, according to virologists.
The chef had been to Beijing many times in recent months, and had been to several Beijing restaurants and other amusement venues, but did not show any symptoms.
The confirmed patient had been in contact with the chef at work.
The chef tested IgM positive, meaning he was infected with COVID-19, but as he showed no symptoms, he should be categorized as an asymptomatic patient, Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University, explained to the Global Times on Monday.
The chef was very contagious in the early stages of infection, Yang said, noting that it was necessary to conduct an epidemiological investigation into him.
Previously, the confirmed patient said he had no history of travel in the 14 days prior to the onset of his illness, and no contact history with any confirmed or suspected cases, leading to public fears over his unknown source of infection.
The patient had been washing dishes in the hotel since May 30, and occasionally cleaned frozen seafood.
Tianjin has traced 9,966 people with connections to the Xinfadi market as of June 20, all of whom have tested negative for COVID-19. The samples taken from local seafood markets also tested negative as of June 20.
Experts have come up with various theories for how the patient contracted the disease, saying he could have been infected by anyone entering China with the virus, by someone coming from high-risk areas in Beijing, handling contaminated frozen food or being in an infected environment.
Chinese health officials had said that the strain of virus in Beijing's Xinfadi wholesale food market has the European origin, but "is older than the virus currently spreading in Europe."
