United States agencies in charge of food safety have taken aim at a controversial theory backed by Chinese health officials, with a new statement saying there is no evidence Covid-19 can spread via food and food packaging. “After more than a year since the [Covid-19] outbreak was declared a global health emergency, [we] continue to underscore that there is no credible evidence of food or food packaging associated with or as a likely source of viral transmission,” the heads of the US Food and Drug Administration and Department of Agriculture said in a joint statement on Thursday. Few countries have been concerned about this potential kind of transmission, as Covid-19 is known to principally spread via droplets in the air when people are in close contact. But in China, where local disease spread is limited, it has become central to disease control measures . Millions of packages of imported frozen foods have been disinfected on entry into China and hundreds of thousands of samples tested for traces of the Covid-19 virus. Foreign food companies who have run afoul of requirements faced bans. Chinese health authorities said they linked several infections among food workers in the country to contaminated frozen salmon, cod, and pig heads, citing positive swabs and no clear alternative source of infection. They have also raced to track down goods they say test positive, with Saudi shrimp, Chilean cherries and ice cream made with Ukrainian milk powder among goods highlighted in local news. But scientists around the world say there is no clear proof that the infections in China were caused by handling these products. They say while theoretically possible, the risk of a food worker getting sick from touching a package that had been coughed or sneezed on by a sick person in another country, would be incredibly low. The US joint statement hit that point again. “Considering the more than 100 million cases of Covid-19, we have not seen epidemiological evidence of food or food packaging as the source of Sars-CoV-2 transmission to humans,” said acting USDA secretary Kevin Shea and acting FDA commissioner Janet Woodcock. “Furthermore, transmission has not been attributed to food products or packaging through national and international surveillance systems.” China’s Covid-19 origin theory includes pig heads and frozen fish The statement mentioned the “relatively few reports of the virus being detected on food and packaging”, but said most studies focused primarily on the detection of viral traces, rather than evidence of human infection. In China, the standard testing method used on imported goods does not indicate whether a virus is still infectious. In one case, scientists were able to isolate a so-called “live” virus off food packaging, which they linked to infections in two food handlers. “Given that the number of virus particles that could be theoretically picked up by touching a surface would be very small and the amount needed for infection via oral inhalation would be very high, the chances of infection by touching the surface of food packaging or eating food is considered to be extremely low,” the agency heads said. The statement comes as the controversial theory was given airtime at a World Health Organization media briefing in China this month, where an international team of scientists investigating the origins of Covid-19 presented findings alongside Chinese authorities. At the briefing, an official at China’s National Health Commission, Liang Wannian, suggested the virus could have originally been carried on imported frozen goods into Wuhan, the city where it was first identified in 2019. Peter Ben Embarek, the WHO official leading the international team, appeared to lend credence to the theory, saying such transmission deserved further study. He later clarified in an interview with Science magazine that it was “worth exploring” whether people in China were being infected this way now. However, it was “not a possible route of introduction” in 2019, when there were not widespread outbreaks of Covid-19 in food factories around the world, he said. US FDA and Centres for Disease Control and Prevention as well as the World Health Organization have long said in their guidance for consumers that there was no evidence people could catch Covid-19 from food. They do recommend handwashing before eating and hygiene measures for food businesses. The WHO-linked International Commission on Microbiological Specifications for Foods also concluded in September that “despite the billions of meals and food packages handled since the beginning of the Covid-19 pandemic”, there was no evidence that food, food packaging or food handling was a source or important transmission route for the disease. The US has also pushed back on the theory, and China’s related import requirements, at the World Trade Organization .