In January, World Health Organization–designated scientists departed for China to investigate the origins of COVID-19. After spending four weeks in-country (including two weeks under quarantine), the international scientists held a joint press conference with their Chinese counterparts on February 9, announcing preliminary findings that were widely received as a public relations victory for China. The WHO-China joint study supported the natural outbreak theory, legitimized the claim that the novel coronavirus could have reached China through imported frozen food, and discarded the hypothesis that the virus had escaped from a laboratory.

The same findings, however, convinced critics of the Chinese government that the investigation was neither independent nor transparent. In a statement issued on February 13, U.S. National Security Adviser Jake Sullivan expressed “deep concerns” about how the scientists had reached and communicated their findings. Because of the controversy, the official release of the WHO-China joint study was delayed until yesterday, March 30.

The 319-page report does not reach conclusions significantly different from those presented in February, but it does offer a wealth of information about the origins of the COVID-19 pandemic. Moreover, the report usefully documents the information the WHO team acquired during its trip, highlighting what more would be needed in order to make a definitive judgment about the origins of the outbreak. The report and the mission serve to illuminate the vulnerabilities and obstacles the WHO faces in addressing global health security.    

One Virus, Three Hypotheses

From the beginning of the pandemic, many scientists pointed to natural zoonotic transmission as the most likely path by which the novel coronavirus first reached human hosts. Historical patterns by which other human coronaviruses had emerged, as well as the genomic sequence of SARS-CoV-2, suggested that the virus had jumped from an original animal source to human beings directly or via an intermediate host species. Bats and pangolins have harbored the known viruses most closely related to SARS-CoV-2, but those pathogens are not sufficiently similar to SARS-CoV-2 to serve as its direct progenitors. The joint team concluded that direct zoonotic transmission was “possible to likely” but that the possibility the virus was introduced through an intermediate host was “likely to very likely.”

The problem is that scientists thus far cannot pinpoint which animal served the role of intermediate host. Researchers tested domestic and wild animals throughout the country but did not find samples that were positive for SARS-CoV-2. According to the report, researchers will continue studying more animal species, in China and other countries, in search of a coronavirus related to SARS-CoV-2.

If the virus did not pass to people through live animal hosts, what might be the alternative? Chinese state media early on offered the hypothesis of “cold-chain transmission.” The theory holds that the virus jumped to humans through frozen products, implying that the virus could have arrived in China through goods imported from another country. According to the report, “Food-chain transmission can reflect direct zoonotic transmission, or spillover through an intermediate host. Meanwhile cold chain products may be a vehicle of transmission between humans.” Such a transmission path could also allow for the possibility that the virus was human engineered.

The virus can survive in cold and frozen environments, and wet markets in Wuhan sold frozen animals. Chinese scientists conducted studies that identified seemingly significant correlations between confirmed cases and cold-chain goods in the Huanan Seafood Market, with people who had spent time in stalls with cold-chain goods 3.3 times likelier to get sick than those who had frequented stalls without cold-chain goods. The scientists also identified in Wuhan, from September through December 2019, a total of 440 kinds of cold-chain products imported from 37 different countries or regions. In addition, the WHO report noted that index cases in recent outbreaks in Beijing, Dalian, and Qingdao were linked to the cold chain and that the virus had been identified on imported products and packages this past year. 

The joint WHO-China study found least convincing the hypothesis that the novel coronavirus escaped from a laboratory.

These findings point to alternative pathways of virus introduction. According to Liang Wannian, the lead Chinese scientist for the joint study, cold-chain transmission could have played “an important role” in the spread of the virus. But the report also said that “there is no conclusive evidence for foodborne transmission of SARS-CoV-2, and the probability of a cold-chain contamination with the virus from a reservoir is very low.” Much as with the natural transmission hypothesis, exploring the cold-chain hypothesis entails retrospective testing—in this case, of available frozen food products manufactured in 2019 and supplied to the Huanan market. Researchers would then need to trace the source of the frozen products and animals that were in Wuhan wet markets in December 2019.

The joint WHO-China study found least convincing the hypothesis that the novel coronavirus escaped from a laboratory. Biosafety has long been a concern in China: in 2004, SARS twice escaped a Beijing lab affiliated with the Chinese Center for Disease Control and Prevention. In November 2020, more than 6,600 people in northwestern Gansu Province were found to be infected by brucellosis, a bacterial disease that spread from a leak at a vaccine plant in the city. Chinese scientists have identified lax biosafety regulation as a concern even in high-level biosafety labs such as the Wuhan Institute of Virology. Before the pandemic, scientists at the WIV had been working on CoV RaTG13, the closest known strain to SARS-CoV-2. Beginning in April 2020, top officials in the administration of U.S. President Donald Trump promoted a theory that the novel coronavirus had escaped a Wuhan lab. President Joe Biden’s administration has confirmed some of the facts behind this claim and suggested that more probe is needed to evaluate the lab’s role in the outbreak.

Scientists participating in the joint WHO-China study, however, unanimously deemed a lab leak “extremely unlikely.” In order for a lab leak to be responsible, the virus would have to have been purposely engineered or accidentally cultured in the lab prior to December 2019, and the scientific community has dismissed both possibilities. The report also suggests that the three labs in Wuhan all upheld stringent protocols that would have prevented any accidents. The director of the WIV, when meeting with the WHO team, denied that the viruses cultured in the lab there were closely related to SARS-CoV-2. She assured the team that there were no “reports of unusual diseases” among her staff, all of whom tested negative for SARS-CoV-2 antibodies.

The joint study, according to the head of the Chinese team, had put the lab escape theory to rest, and “future virus origins-tracing missions will no longer be focused on this area, unless there is new evidence.” But not everyone in the scientific community was satisfied. Twenty-six scientists from the United States, Europe, and Australia signed an open letter in early March contending that the WHO-designated scientists lacked the necessary training and forensic skills to fully investigate the lab escape scenario. Skeptics pointed to reports that some Chinese researchers at the WIV fell sick in fall 2019 (the WHO-led team was quick to point out that these staff members tested negative for the coronavirus).

Amid criticism that the lab escape hypothesis was ruled out hastily and with inadequate information, WHO Director General Dr. Tedros Adhanom Ghebreyesus stated that “all hypotheses are on the table and warrant complete and further studies.” According to the scientists who signed the open letter, further investigation involves expanding the team to include forensic investigators and biosafety and biosecurity experts, who should have “full or significant access” to labs and institutions known to have worked on coronaviruses, their records and samples, and employees of the labs in 2019.  

The When and Where

The WHO team sought to settle the questions not only of where the virus came from but exactly when it first struck and in what location. Chinese scientists had found that the first confirmed case (“patient zero”) became ill on December 8, 2019. A review of genomic, epidemiological, clinical, and sentinel surveillance data collected by Chinese scientists does not support the extensive circulation of the virus in the months before the COVID-19 outbreak in Wuhan. That said, the data collection process has not been flawless. Chinese scientists examined medical records of more than 76,000 patients with respiratory conditions in October and November 2019, among whom 92 hospitalized patients were identified as suspected COVID-19 cases. None of them tested positive for antibodies to COVID-19.

International scientists have pointed out that the small number of suspected cases might be a function of stringent clinical criteria that would likely exclude patients with milder illness.  Moreover, scientists tested the patients’ antibodies only a few weeks before the WHO team’s arrival, by which time they might have faded to an undetectable level. The report recommended a further joint review of the data and further testing of relevant specimens.

But if the report cautiously reinforced earlier conclusions about when the virus emerged, it did not evince as much certainty about where. Until late November 2020, the WHO maintained it was “highly speculative” that the virus did not emerge in China. The Huanan Seafood Market, which sold live animals before it shut down on January 1, 2020, was initially suspected to be ground zero for the virus. But current data suggest the market acted more as an “amplifying event.” Of the 174 notified cases in December, only 28 percent had a history of recent exposure to the market only. Patient zero was said to have no connection to the market. Extensive testing of animal products in the market found no evidence of animal infections, either.

The WHO team did observe that patient zero’s parents (who later tested negative for COVID-19) had visited a different wet market and that Chinese health authorities did not trace their contacts there. Likely for this reason, the report recommends more interviews and serological testing of people connected to the wildlife farms that supplied the wet markets linked to positive cases in Wuhan. Those suggested for study include “farmers and their workers, vendors, delivery staff, cold-chain suppliers and other relevant people and their close contacts.”

The joint team further reviewed studies and reports suggesting that the virus had circulated in other countries even before the first confirmed case in Wuhan. The team recognized that these studies were limited in nature and recommended systematic, retrospective research on “earlier cases and possible hosts for SARS-CoV-2 around the world.” In making this recommendation, the report’s authors echo China’s official narrative on the origins of the pandemic—but their work also clearly shows the need for further research on the same subject within China.

What the Investigation Reveals

For all the questions the joint report raises, it also sheds important light—some of it on the flaws in the health governance regime itself. The WHO is the lead international organization on global health security and rightfully belonged in the driver’s seat in investigating the origins of the pandemic. But it should have been diplomatically and politically savvier in dealing with those who held critical stakes in the investigation. The WHO Secretariat reportedly failed to consult its 34-member executive board before or during the negotiation with China over this mission. In selecting scientists to join the mission, it rejected those the United States government nominated. The terms of reference the WHO signed with China essentially reduced the investigation to a joint study, in which the WHO-led team did not have the mandate or access it would have needed to investigate the outbreak independently and thoroughly. Even WHO officials themselves admitted that the mission was to “design and recommend scientific studies, not to do an investigation, let alone a forensic audit of laboratories.” 

The episode also showcases deficiencies in the International Health Regulations, the law that governs the international response to global public health emergencies. The investigation into the pandemic’s origins was supposed to comply with the IHR and to be transparent and hold all actors accountable. But the WHO did not have unfettered access to China and was instead compelled to allow Beijing to set the investigation’s pace and agenda and approve its final report. The IHR does not have teeth to enforce its norms, especially in authoritarian states that value secrecy and obedience.

The Chinese government holds a political stake in the matter of the pandemic’s origin. As a result, the distilling and disclosing of information relevant to the investigation risks following a logic of realpolitik rather than of scientific necessity or peer review. By the time the mission took place, a full year had elapsed since the initial outbreak and much of the critical information was gone. The WHO couldn’t gather intelligence independently, so for data and analysis it had to rely on Chinese scientists, whose work is at the mercy of the very state that sought to determine the parameters of the investigation. When the international scientists requested access to the raw data of the more than 76,000 respiratory patients from the fall of 2019, their Chinese counterparts refused, appealing to the need to protect the privacy of patients.

Right before the WHO team arrived, China’s government began to promote the idea that the COVID-19 pandemic was likely caused by “separate outbreaks in multiple places.” The results of the WHO-led joint study do not prove this claim, but they do recommend expanding the inquiry to other countries. A Chinese Foreign Ministry spokesman seized on this recommendation to question when the WHO experts would be invited to access the U.S. military lab in Fort Detrick, where Chinese state media indicated the pandemic might have originated, even though the same WHO report has invalidated such a hypothesis.

The United States and European Union have greeted with suspicion a study that was neither thorough nor independent. The world may never discover how the pandemic started, but hopefully the episode will create urgency to reform the WHO and strengthen the IHR so that future global health emergencies are arrested in their infancy.

UPDATE APPENDED (April 5, 2021)

The author's bio has been edited to include information about a funding source. 

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  • YANZHONG HUANG is Senior Fellow for Global Health at the Council on Foreign Relations, a Professor at Seton Hall University’s School of Diplomacy and International Relations, and Director of the school’s Center for Global Health Studies. This article is part of the Diamonstein-Spielvogel Foundation Project on the Future of Democracy.
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