Recent Beijing Covid-19 cluster from European strain of virus – genome data

China has released genome sequencing data for the coronavirus responsible for a recent outbreak in Beijing, with officials saying on Friday it identified a European strain based on preliminary studies.

China, which had been under pressure to make the data public sooner rather than later as Covid-19 cases mount in the country's capital, said it had also submitted the data to the World Health Organization (WHO).

The US administration has blamed the Chinese government for not handling the initial outbreak in central China properly and moving too slowly to contain the epidemic, leading to mounting cases and deaths in the United States. China has rejected that accusation, saying it wasted no time in releasing information about the epidemic including the genome sequence of the initial coronavirus outbreak in Wuhan.

The US has also accused of downplaying the current Beijing outbreak.

In the latest Beijing outbreak, the WHO said on Sunday it had been informed by the Chinese of ongoing investigations into the source of the cluster and the extent of the infections. It requested for the genetic sequences to be released as soon as possible.

The genome sequencing was published late on Thursday and had also been shared with the WHO and the Global Influenza Data Initiative, said the Chinese Center for Disease Control and Prevention (CDC).

How does gene sequencing help?

Virus genome sequencing is a vital and rapidly-developing tool in the diagnosis of the disease Covid-19 and in understanding the spread and control of the new coronavirus.

Details published on China's National Microbiology Data Center website revealed the Beijing genome data was based on three samples –– two human and one environmental –– collected on June 11.

That was the same day the Chinese capital reported its first new local Covid-19 infection in months. In the eight days since, Beijing has reported a total of 183 cases, linked to the sprawling wholesale food centre of Xinfadi in the city's southwest.

Xinfadi supplies more than 70 percent of Beijing's fresh produce and has been temporarily closed due to the cluster.

READ MORE: Wholesale food markets' hygiene called into question after Beijing outbreak

European strain differs from current virus in EU

"According to preliminary genomic and epidemiological study results, the virus is from Europe, but it is different from the virus currently spreading in Europe," CDC official Zhang Yong said in an article published on Friday.

"It's older than the virus currently spreading in Europe."
Zhang said there were several possibilities as to how the virus arrived in China.

"It could have been hidden in imported frozen food products, or it was lurking in some dark and humid environment such as Xinfadi, with the environment not having been disinfected or sterilised," Zhang wrote in the article posted on the Central Commission for Discipline Inspection's website.

Not from Beijing

Wu Zunyou, the CDC's chief epidemiology expert, had told state media earlier this week the Beijing strain was similar to Europe's, although not necessarily directly transmitted from European countries.
Wu did not elaborate on those comments made before the release of the genome sequence.

The coronavirus strains found in the US and Russia were mostly from Europe, he added.

The first major cluster of new coronavirus infections was traced to the Huanan seafood market in Wuhan in December. It has since spread globally, infecting almost 8.5 million people and killing around 450,000.

On tracing the origins of the strain that hit Beijing, Wu said the virus did not originate from the Chinese capital.

"It must be some people or goods outside of the city that carried it into the (Xinfadi) market," Wu said in an interview with state television aired on Friday.

"It's unclear who, or what kind of goods, had brought the virus into Beijing." 

Too early to tell

Scientists cautioned against making early conclusions on the Beijing cluster.

Ben Cowling, a professor at the University of Hong Kong's School of Public Health, said: "it is possible that the virus now causing an outbreak in Beijing had travelled from Wuhan to Europe and now back to China."

But he said the first case has not yet been identified and it may be too late to find out how this outbreak started. 

Francois Balloux, a professor at University College London wrote on Twitter that –– based on the data shared –– there had been local transmission for some time before the outbreak was identified.

"Their position in the tree does not allow to confidently assign a geographic origin to the lineage. They could have originated from essentially anywhere," he wrote.