Early in the morning of August 16, a 41-year-old man from Chongqing Municipality in west central China got up and went jogging along a lake in a local outdoor park – some something that should have been pleasant, if not banal. , exit. But what really happened during that 35-minute jaunt has now sparked international alarm and debate, with some scientists doubting China’s startling tale.
According to the Chinese Center for Disease Control and Prevention, the unmasked man infected 33 unmasked park visitors and two unmasked park employees with the omicron coronavirus subvariant BA.2.76 during his short run. The agency claimed the transmission occurred during fleeting outdoor encounters as he walked past people on a four-metre-wide pathway. Many more have been infected without any close encounters. Twenty of the 33 park-goers infected were infected by simply visiting outdoor areas of the park that the jogger had previously passed through, including an entrance gate. The two infected workers, meanwhile, quickly spread the infection to four other co-workers, bringing the total number of outbreaks in the jogger’s park to 39.
To support these unusual findings, the CCDC cited case interviews, park surveillance images and genetic data on SARS-CoV-2, which would have linked the cases but are notably missing from the report.
The report’s claims, if accurate, would suggest that a significant update is needed for our current understanding of SARS-CoV-2 transmission risks. Although outdoor transmission is known to be possible, it is considered much less likely than indoor transmission, where virus particles can hang in stagnant air and collect in enclosed spaces over time. time. Outdoor encounters that are transient are particularly not considered a significant risk, as vast volumes of moving air quickly disperse infectious doses of virus particles. For the same reason, SARS-CoV-2 is not thought to linger in the threatening clouds outside in the wake of an infected person.
For now, experts outside China are not revising their thinking on transmission risks, citing missing genetic data from the report and other questionable findings.
Missing data
Given China’s strict “zero COVID” strategy, the CCDC flatly dismissed the possibility that the infections were part of an undetected outbreak in the greater community, calling exposure to the jogger (aka “patient zero”) of “only possible exposure”.
The CCDC says genetic data links all the cases together, showing that patient zero was the source of all 39 infections. Specifically, they report that 29 of the 39 cases had “exactly the same genetic sequencing as patient zero; 5 cases had a mutation site added to patient zero’s genetic sequence; and the other 5 cases could not be sequenced. due to unqualified specimens”. But there’s no sequencing data included in the report, and it’s unclear what sequencing was actually performed to back up their claims.
“If they had sequence data showing that 29 cases had genomes identical to ‘patient zero,’ that would suggest that all the cases came from a single source,” virologist Angela Rasmussen told Ars. Rasmussen is a research scientist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan and affiliated with the Georgetown University Center for Global Health Science and Security.
“But,” she said, “it’s unclear whether they did full genome sequencing of all cases, what sequencing platform they used (Illumina vs. Nanopore), etc.” The report only mentions “gene sequencing”, which may only suggest partial genome sequencing, not “whole genome sequencing” which would certainly indicate a direct link between the cases. Without knowing the data and sequencing methods, it is impossible to confirm whether the jogger was the source.
The CCDC also offers a confusing explanation of how Jog’s patient zero got infected in the first place.
patient zero
According to the CCDC, the man was infected following a wave of “exposure to contaminated airline environments”. The man had traveled from Chongqing to the northern city of Hohhot on August 11 and returned to Chongqing on August 13, three days before his jog. Neither flight had known cases of SARS-CoV-2 on board that could explain the human’s infection. But, the plane he took for the return trip had carried four SARS-CoV-2 positive passengers the previous day, August 12.
On August 12, four passengers from Tibet flew from Chongqing to Hohhot and later tested positive in Hohhot. The plane, meanwhile, was not disinfected after their flight, and the Chongqing man boarded the next day and sat (in seat 33K) near where three of the infected passengers were seated (seats 34A, 34C, 34H). It is unclear how humans could have been infected this way – SARS-CoV-2 is not known to persist in the air for such long periods, and transmission from contaminated surfaces is rare. Moreover, the report does not indicate that other passengers on the flight were also infected, including people who were actually seated in the same seats as the passengers from Tibet. But patient zero was infected with BA.2.76, which was circulating in Tibet, leading the CCDC to make a connection.
“I think it’s also very doubtful that ‘patient zero’ got infected on that plane,” Rasmussen said. “I noticed that the previous flight with the passengers who were believed to be the source of the infection were from Chongqing – this might suggest cryptic spread of BA.2.76 to Chongqing, not (only) Tibet as the paper claims In this case, if a whole bunch of people in Chongqing have BA.2.76, the sequencing data might just point to a much larger outbreak in Chongqing, but you’d need the actual sequencing data to really understand what’s going on. .
“Bottom line: any assertion about what the data actually shows depends on the actual inclusion of the data in the document,” she said. “Otherwise it’s just speculation.”
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