The coronaviruses that sparked a new outbreak in Beijing probably originated from Europe, according to the Chinese government and independent researchers using newly released genetic sequences.
“The results of preliminary genetic sequencing research show that this virus came from Europe . . . but is older than the viruses currently circulating in Europe,” said Zhang Yong, an assistant director within China’s Centre for Disease Control and Prevention (CDC), in a government notice on Friday.
Gao Fu, director of the CDC, had previously told local media the virus could have started spreading in Beijing as early as the start of May.
The latest findings add weight to the idea that the virus behind the latest outbreak had been circulating in the Chinese capital before the first cases were identified last week.
On Thursday, Beijing reported 24 new confirmed infections in an outbreak that started at the city’s Xinfadi food market. The rate of spread appears to have slowed from last weekend, when about 40 infections were found each day, prompting authorities to lock down districts across the city and impose travel restrictions.
The disclosures also highlight the challenge of containing a second wave of Covid-19, even for governments that have controlled the initial outbreak. Before last weekend’s cases, Beijing had had no confirmed symptomatic infections for almost two months.
“Strict epidemic preventions and controls will still have leaks,” said Jin Dong-Yan, professor of precision medicine at Hong Kong University. “This is the characteristic of this virus, and we have to be fully prepared.”
Prof Jin added there was no need to shut down more borders. Foreign nationals have not been able to enter China since late March.
“This virus has already come in for some period of time. If it had only been present for a short time, it likely wouldn’t have spread to such a large area,” he said.
The disclosures come a day after Chinese authorities publicly released the full genomic sequence of the novel coronaviruses found in the Xinfadi market.
Nextstrain, an international mapping project that tracks viruses as they spread and mutate, classified the strain found in Xinfadi as similar to the novel coronaviruses found in Europe.
“The Beijing outbreak . . . is related to viruses circulating in Europe,” Nextstrain wrote on Twitter, classifying it as part of the European “clade” or family of viruses.
Nextstrain added that, when comparing it with other viral strains globally at a higher level of abstraction, the “nearest sequences” are from the Czech Republic, Taiwan, Greece and Portugal.
Of the three virus strains found in Beijing’s new outbreak, one appears to be the “parent” of the other two, according to the genetic sequences published.
The two “child” viruses have both mutated twice, suggesting that they had been reproducing for some time before Beijing’s most recent outbreak.
“We can’t exaggerate what we know, although this is all reasonable speculation,” said Prof Jin, adding that epidemiological survey data would be needed — such as tracking groups of people associated with the Xinfadi market — to explain the origin of the Beijing outbreak.
Additional reporting by Nian Liu in Beijing and Xueqiao Wang in Shanghai
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