TEST POINTS TO NEW SOURCE OF OUTBREAK

Omicron infections in Tianjin found to have a different origin to previously imported cases, as authorities are studying contamination links

Genome sequencing has shown that an ongoing Omicron outbreak in Tianjin has a different source to previously imported cases, according to a senior official at the city’s Centre for Disease Control and Prevention (CDC).

Zhang Ying, deputy director of the Tianjin CDC, told state broadcaster China Central Television (CCTV) the Omicron strain circulating in the city might have come from another part of the country or was transmitted through imported goods or other environmental contamination sources.

Zhang said the strain now in the city did not share the same source as the earlier imported cases in Tianjin.

Tianjin has tested almost 12 million people since Sunday morning, detecting 77 new cases among the results for nearly 7.9 million people so far.

That pushed the total number of positive cases in the city’s Omicron outbreak to 97, of which 90 are from Jinnan district. Some 49 patients were symptomatic and 15 asymptomatic. Another 33 tested positive and are awaiting confirmation. In Tianjin, schools are the hotbed of infections and all classes in Jinnan district have been suspended.

Epidemiologist Li Lanjuan called for efforts to speed up the vaccination of children. The mainland has been vaccinating children above the age of three.

According to China CDC Weekly online publication on December 13, a 35-year-old man and a 17-year old student flying from Warsaw, Poland, to Tianjin were found carrying the highly transmissible Omicron strain.

But Zhang said there might be another source for the outbreak. “We cannot … rule out that the virus is imported directly, because the spread of virus is not only through humans, but it can be spread via objects or environmental [contamination]. We are still investigating other possibilities for the virus to be imported to Tianjin directly,” she said.

“There is another option – would it be possible that it is not imported but came from other areas [in the country] and spread to Tianjin? We are tracing this simultaneously and we have found some clues already.”

Experts previously suggested that cold chain or other contaminated imported goods could be a source of infection, although most overseas scientists said the chance of transmission through that method was very slim.

Han Jinyan, deputy director of Tianjin’s health commission, said the patients in the city were aged between five and 74. The first case showed symptoms on December 29. Clusters emerged from January 6 and the virus spread at events such as funerals and venues such as schools.

Among the patients, three people had had one shot of a vaccine, 76 had received two doses and 20 had received boosters.

All but one of the children confirmed with the virus were vaccinated.

Han said community transmission was going undetected in the city. Zhang said the Omicron strain might have been “hiding” in the city for some time.

An Omicron infection could spread from one person to the next just two to three days after the first patient was infected, making it possible for three generations of the virus to spread in 15 to 20 days.

Zhang said it was difficult to trace the origin because many carriers were asymptomatic or had mild symptoms.

On Sunday, Anyang in Henan province reported two Omicron cases traced to a student from Tianjin, but it was discovered nearly two weeks after the strain had spread to the inland city.

By 6pm on Monday, 31 symptomatic and 10 asymptomatic cases were reported in Tianjin.