I. Contributing Chinese Wisdom to the Study of the Origins of SARS-CoV-2

1. China's Efforts in Tracing the Origins of the Virus

Since the outbreak of the pandemic, China has consistently dedicated substantial resources to collaborative studies into the origins of the virus, involving both Chinese and international scientists. Upholding its international responsibilities with openness and transparency, the country spearheaded research initiatives in critical fields such as clinical epidemiology, molecular epidemiology, environmental epidemiology, and the identification of animal hosts. Demonstrating a strong sense of global responsibility, China closely collaborated with the WHO on the study of the virus origins, and in 2020 and 2021, invited WHO expert missions to China to carry out a joint study into this field.

In July and August 2020, Chinese experts held preparatory consultations with their WHO counterparts concerning cooperation in scientific research on virus origins tracing in China, and together outlined the "WHO-convened Global Study of Origins of SARS-CoV-2: China Part – Terms of Reference". From October to December 2020, Chinese scientists held four virtual meetings with a WHO-assembled team of international experts to share updates on global SARS-CoV-2 origins research and to align methodologies for the joint study.

In January and February 2021, a 28-day joint study was conducted in Wuhan, China, by a team of 17 Chinese experts and 17 international experts from the WHO, the World Organisation for Animal Health (Office International des Epizooties) and several countries. On February 9, the joint team held a press conference to announce key findings from their study.

On March 30, 2021, the WHO organized a member state information session and press conference to present the findings about the origins of the virus and published the "WHO-convened Global Study of Origins of SARS-CoV-2: China Part – Joint WHO-China Study" on its website.

From 2021 onward, the WHO started to build a Scientific Advisory Group for the Origins of Novel Pathogens (SAGO). Meanwhile, China has allocated resources to advance comprehensive and in-depth research and analysis in epidemiology, molecular epidemiology, animal and environmental studies, and laboratory audit, as outlined in Phase 2 of the "Joint WHO-China Study". Chinese scientists have shared progress and findings with the international scientific community and other professionals through reports to the WHO and SAGO or papers published on Chinese and international academic journals.

To date, no findings have contradicted the conclusions of the "Joint WHO-China Study". It is fair to say that the study on the origins of SARS-CoV-2 conducted in China has ended.

The WHO-convened global study of origins of SARS-CoV-2: China part has produced extensive research results. Its methodology and scientific findings have laid the foundations and provided guidance for similar efforts in other countries.

Tracing the origins of SARS-CoV-2 is a scientific endeavor that must not be politicized or exploited as a means of stigmatization by any country. The global community should encourage research institutions and professionals of all countries to share evidence and conduct systematic studies. Above all, pandemic prevention should be a priority, as similar outbreaks in the future could pose another catastrophic threat to human health and security.

2. China's Open and Transparent Updates on Its Findings Regarding the Origins of the Virus

In 2020, a study on the time to the most recent common ancestor of SARS-CoV-2, conducted by scientists from the Chinese Academy of Sciences and collaborating teams, indicated that the outbreak in Wuhan likely occurred between mid-November and early December 2019. This timeline aligns closely with the onset date of the first reported Covid-19 case – December 8 of that year.

After the joint WHO-China study concluded in 2021, Chinese scientists made another spatiotemporal distribution analysis of 76,000 screening records from medical institutions and 174 early confirmed cases. The analysis revealed no evidence of unusual clusters of respiratory illnesses in Wuhan between October and early December 2019.

In a 2022 serological and epidemiological study, Chinese scientists detected no specific antibodies against SARS-CoV-2 in 43,850 blood donation samples collected in Wuhan between September 1 and December 31, 2019. These findings provided evidence that the virus was not present in Wuhan prior to December 2019.

A number of research teams in China conducted systematic testing on more than 80,000 samples collected from bats, pangolins, wild birds, wild boars, raccoon dogs, and other wildlife, as well as livestock and poultry across the country. Sample collection spanned from 2017 to 2021, and the analyses detected no evidence of SARS-CoV-2 circulation in these animal populations. Additionally, in early 2020, scientists from the Chinese Academy of Medical Sciences screened bat species in Wuhan and its surrounding areas and found no virus genetically related to SARS-CoV-2. These findings effectively ruled out the possibility that this virus originated from local wildlife in the Wuhan vicinity.

In 2023, a paper published by the Chinese Center for Disease Control and Prevention showed that all 457 animal samples collected from the Huanan Seafood Wholesale Market in the early stage of the epidemic tested negative for SARS-CoV-2, while 74 out of 923 environmental samples from the market were positive. Genomic sequencing of three isolated viral strains revealed 99.9-100 percent genetic identity with early Covid-19 cases, indicating that viral shedding by infected individuals was the likely source of contamination in the market environment.

Source tracing of outbreaks in clusters in locations other than Wuhan between 2020 and 2022 revealed the likelihood of introduction from overseas through cold-chain transportation. In June and July 2020, new outbreaks emerged in Beijing's Xinfadi Agricultural Products Wholesale Market and Dalian, Liaoning Province. It is worth noting that prior to these outbreaks, no new cases had been confirmed in Beijing and Dalian for 56 and 111 consecutive days, respectively. In addition, Beijing's early cases were primarily concentrated among stallholders from the aquatic products section in Xinfadi market, while those in Dalian involved aquatic product processing workers in a seafood company. Several tracing investigations indicated that the virus originated from other countries and regions and subsequently entered China via cold-chain transportation.

On September 24, 2020, two stevedores in Qingdao, Shandong Province were diagnosed with Covid-19. The two cases had no travel history or contact with other confirmed cases. The only epidemiological link was their involvement in handling the same batch of imported frozen food products on September 19, 2020. Several samples from the outer packaging of the frozen food products tested positive for SARS-CoV-2 nucleic acids. Whole genome sequencing confirmed that the virus detected on the packaging was the source of infection for the two cases, and viable virus from the packaging was successfully isolated and cultured. This marked the world's first successful isolation of viable SARS-CoV-2 from cold-chain food packaging, demonstrating cold-chain transportation as a transmission pathway for SARS-CoV-2.

Given that the early confirmed cases in Wuhan were concentrated in the aquatic products section of Huanan market, there is a possibility that the outbreak in the market at the end of 2019 was introduced to China from abroad via cold-chain transportation.

These findings were published in the "Joint WHO-China Study" and international journals including The Lancet, Nature, Cell, National Science Review, Scientific Reports, and Virus Evolution. With solid laboratory data supporting the likelihood of four possible introduction pathways, the study concluded:

• Direct zoonotic spillover is considered to be a possible-to-likely pathway;

• Introduction through an intermediate host is considered to be a likely to very likely pathway;

• Introduction through cold/food chain products is considered a possible pathway;

• Introduction through a laboratory incident was considered to be an extremely unlikely pathway.

China's fully open and collaborative stance demonstrates its commitment to scientific principles and integrity, and its responsibility for building a community of health for all.

China has actively participated in global virus origins-tracing efforts with the greatest sincerity, as it firmly upholds that the truth does not lie in premature accusations but in meticulous data-based verification. Through systematic epidemiological investigations, molecular tracing, animal host screening, and studies on cold-chain transmission, the possibility of Wuhan being the natural origin of SARS-CoV-2 was scientifically ruled out. These efforts have provided the global scientific community with critical empirical evidence and established a research paradigm for future studies.