The central Chinese city of Wuhan grabbed global attention almost a year ago after cases of a mysterious virus were reported. Later, as COVID-19 cases were also spotted in other parts of the world, with some countries suffering from the relentless onslaught of COVID-19, some Western politicians and media sought to shift the narrative from their own shortcomings by targeting and accusing Wuhan as being “where the coronavirus began.”

Our understanding of the new virus has deepened over the past few months, and as the mounting sporadic outbreaks in China were found to be related to imported cold-chain products, with other parts of the world, including Europe and the American continent, reportedly discovering signs of the coronavirus earlier than Wuhan, it begs a new hypothesis: did the early outbreak in Wuhan originate from imported frozen food?

To dig deeper, Global Times reporters visited Wuhan and talked with merchants from the Huanan Seafood Wholesale Market, where the earliest cluster infections in the country were reported, as well as prominent virologists and epidemiologists. Although it might be too early to jump to conclusions, the possibility that the coronavirus was passed on from cold-chain products into Wuhan, or more specifically, to the Huanan wet market, where the sale of frozen products was once prevalent, cannot be ruled out. Yet more evidence is needed, and scientists worldwide are urged to join hands to further research this hypothesis and pinpoint the origin of the virus. This is the second investigative story the Global Times has conducted as the year draws to a close. The first was an in-depth depiction of the strict measures China has enforced to prevent new risks from cold-chain food imports.

For months now, the mounting flare-ups of COVID-19 in China have been tied to imported frozen products and even shipping containers as Western countries face the onslaught of a new wave of outbreaks as winter comes to the Northern Hemisphere. The repeated pattern of outbreaks in China has triggered a new possibility: was the outbreak in Wuhan’s Huanan wet market, where the earliest cluster infections in the country were reported, also caused by imported cold-chain products?

Global Times reporters have conducted a series of investigations in Wuhan and talked with merchants who used to work at the now-closed Huanan wet market, finding that the consumption and sale of imported frozen products were prevalent in this central Chinese city. The repeated infections caused by imported cold-chain products and reports about how signs of coronavirus were found in other parts of the world propelled virologists to think if Wuhan was also the victim of such a transmission route.

Yet those scientists believe that more evidence is needed to further verify this hypothesis, and that scientists around the world should work together to solve the puzzle, rather than being deterred by certain political pressures.

Now that the Huanan wet market has been closed, former shop owners are moving on. Global Times reporters learned that some of these shop owners have moved to another market 17 kilometers away.

Guo, who sells fresh aquatic products, is one of them. She told the Global Times that she worked at the Huanan wet market for more than 20 years before the outbreak. “There was nothing wrong with my products. The authorities had been checking our products twice a month. They did sample examinations of every type of product, nothing was wrong.”

The idea regarding the origin of the virus mystifies Guo, who only heard once that wild animals were sold at the Huanan wet market, but she said those were sold “in secret.” Guo is sure there were many shops selling imported frozen products.

Since China has imposed strict examination rules on cold-chain products recently, Guo said her business as a fresh water products wholesaler has been heavily affected. She now earns less than 1,000 yuan ($153) per day, nearly as half as what she used to. “Actually the frozen products in China are clean. But I don't know about those from abroad.”

On November 22, the Global Times reporters saw a merchant who used to work at the Huanan seafood market unload frozen food at Sijimei market, which was suspected to be imported from Argentina. Former merchants from the Huanan market have created a WeChat group with at least 29 out of the 270 group members selling frozen products, evidence verifying further that the sale of cold-chain products had long existed at the Huanan market.

Global Times reporters found from media reports that stores in the Huanan Seafood Market used to sell imported cold-chain seafood, such as king crab and arctic shellfish, as well as meat products from Brazil and Germany.

The city also imported Australian steak, Chilean cherries and Ecuadorian seafood before 2019, according to the information from the website of the city’s commerce bureau. Statements published by the Hubei Provincial Commerce Department show in 2018 and 2019, foreign trade enterprises have imported meat from Canada, Brazil and Spain. Wuhan customs said that from January to November 2019, Hubei Province, which governs Wuhan, imported 470 million yuan of “frozen products,” up 174.2 percent compared with the same period of the previous year, which marked the fastest increase of all imported products.

In the latest case, the outer packaging of frozen meat imported from Brazil and Uruguay to Wuhan tested positive for coronavirus, said Wuhan CDC on Sunday.

According to reports, Wuhan has imposed strict management measures for imported cold-chain products. Wuhan authorities are required to check several documents, including nucleic acid test results before the products arrive. They also need to conduct further nucleic acid tests on those products, and disinfect them properly, according to the new rules.

The Chinese Center for Disease Control and Prevention said on October 17 that it has detected and isolated living coronavirus in a positive sample from the outer packaging of imported frozen cod while tracing a sporadic outbreak that occurred in East China’s Qingdao.

The discovery confirmed that under special conditions of cold chain transportation outside the laboratory, the coronavirus can survive on packaging for a long time, signaling that the virus can be imported within the cold-chain food transportation process for long distances across borders, and pass to humans.

“The idea never crossed our minds before. But now it seems plausible that the virus may have been imported to Wuhan via imported cold-chain products,” Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University, told the Global Times on Saturday.

He pointed out the coronavirus can live for months in a cold-chain environment where the temperature ranges from -20 to -30 C. Yang said to solve the puzzle, scientists need to know when and from where the cold-chain products were imported, and to compare them with imported cold-chain samples from the Huanan wet market.

If contaminated goods, including food or packaging, are transported in the cold chain from areas with a high COVID-19 incidence, they can bring the virus to non-epidemic areas, thereby causing contact and transmission and triggering a new COVID-19 outbreak, Wu told the Global Times.

If contaminated goods, including food or packaging, are transported in the cold chain from areas with a high COVID-19 incidence, they can bring the virus to non-epidemic areas, thereby causing contact and transmission and triggering a new COVID-19 outbreak, Wu told the Global Times.

Following these clues, it was found that seafood imported from multiple countries was contaminated with the novel coronavirus. Subsequently, Chinese customs authorities in many cities across the country tested imported frozen seafood or meat products and found quite many of these products tested positive for coronavirus.

“Theoretically, it is possible that coronavirus from other countries caused the early outbreak in Wuhan, but we lack evidence,” an anonymous Beijing-based expert told the Global Times. He said that judging by the series of flare-ups across China in the second half of the year, it is possible Wuhan’s outbreak was triggered by imported cold-chain products.

But he also said that the infections occasionally triggered by cold-chain imports in China may be because other countries were severely affected by the virus now. “We cannot conclude so far if the coronavirus existed in other countries before the early cases showed in Wuhan.”

The international community has never ceased discussion about the origin of coronavirus.

Although no final conclusion has been drawn, similar reports that the virus was found in other parts of the world before the Wuhan outbreak have been frequently seen in recent months.

Italian newspaper Corriere Della Sera reported in November that a new coronavirus was circulating in Italy in September 2019, a study by the National Cancer Institute (INT) of the Italian city of Milan shows, indicating that the virus may have existed in Italy months before it was first detected in China.

The Italian researchers’ findings, published by the INT’s scientific magazine Tumori Journal, show 11.6 percent of 959 blood samples from healthy volunteers enrolled in a lung cancer screening trial between September 2019 and March 2020 had developed coronavirus antibodies well before February.

Peter Forster, a geneticist from Cambridge, also told the Global Times that he is not surprised that there might be cases earlier than China.

Foster suggests it is useful to think of three stages in the origins of the coronavirus: when and where did it cross the species barrier from bats to humans and when and where did it start spreading successfully among humans. “My dating suggests sometime between September and December 2019,” said the virologist, proposing finally to look at when the globally dominant infectious coronavirus subtype arose.

“Everyone agrees it was prominent in Northern Italy in February 2020. Some scientists said it came to Italy from China, but I am not so sure,” he said.

Evidence of both epidemiology and virology are needed to find out where the virus comes from, said the Beijing-based anonymous expert. If the pandemic originated from a certain place, there should be signs of an early outbreak. It is also possible that the virus already existed, but not seriously enough to cause an outbreak, he said, noting that there is only a small probability of the latter scenario, and no solid evidence to support it.

From a virology perspective, a full gene sequence of cases from that place should be obtained for observation and for determining when the virus was transmitted to this place via time and the virus’ variation point, said the expert.

“If we have doubts that the virus was originated from places other than Wuhan, we can compare its sequencing with the virus that was found in Wuhan. [We should] compare their homology and variability, to see if the virus found in other places is in its early stage, or it is evolved,” he said.

There are reports from several countries that early blood samples tested positive for the virus, but they can provide no evidence of the nucleic sequence, so the possibility of a false negative cannot be ruled out, said the anonymous expert.

He believes that if antibodies can be found in the blood serum, then the virus can also be found there. Even if the virus is not infectious anymore, it is easily detected, as its nucleic acid is protected by the coat of the virus and it is very stable and sensitive.

Although those virologists have pictured a clear route map to trace the origin of the virus, the real path to finding the origin is laden with difficulties.

The anonymous expert said that in terms of tracing the virus origin, the momentum for international scientists to cooperate has retrogressed compared with the pre-COVID-19 period.

“Scientists are reluctant to become involved in politics, they are eyeing international cooperation. Yet researchers from all over the world are acting with caution, avoiding troubles, and refusing casual communication. I don’t think it’s an ideal atmosphere for cooperation.”

This has drawn attention from international bodies. WHO Director-General Tedros Adhanom Ghebreyesus urged countries on November 30 not to politicize the hunt for the origins of the new coronavirus, saying that would only create barriers to learning the truth.

When talking to Tedros in September, director of China's National Health Commission Ma Xiaowei vowed to enhance cooperation with the WHO on virus prevention, origin tracing and vaccine development. China is pushing forward the work on the virus origin tracing, and is willing to strengthen cooperation and communication with the WHO, Ma said.

Chinese Foreign Ministry spokesperson Zhao Lijian said on November 24 that while tracing the origin domestically, China has been earnestly implementing WHA resolutions.

"We are the first to invite WHO experts in for origin-tracing cooperation." Zhao said, adding that "We hope all relevant countries will adopt a positive attitude and cooperate with WHO like China does, making contributions to global origin-tracing and anti-epidemic cooperation."

“International communication on the virus origin should be frequent and open for all. But some countries weighed in and complicated the issue,” said Yang, who noted that the world has achieved great progress in fighting COVID-19 in the past year, including treatment of the disease and vaccine R&D.

Tracing the virus origin should not be a battle against each other; instead, an information, data sharing mechanism is helpful to bring the virus under control, Yang said.