Fresh questions have been raised over the risks of catching the coronavirus from food after traces were found in at least five samples of ice cream made in the northern Chinese city of Tianjin. Last Thursday, authorities in Tianjin, neighbouring Beijing, said three samples of ice cream had been found to contain traces of Sars-CoV-2, the coronavirus that causes the disease Covid-19. An investigation suggested that Ukrainian milk powder used to make the ice cream was the likely source, after three samples of the powder and two further samples of ice creams from the same batch were also found to contain Sars-CoV-2, from more than 2,800 samples taken from the ice cream, packaging, manufacturing plants and retail stores. Most of the potentially contaminated ice cream had been traced and recalled, but 21 ice creams remained unaccounted for, the authorities said. The World Health Organization (WHO) has said the possibility of catching Covid-19 from frozen food is low, but China has linked infections to imported food. In November, a truck driver, also from Tianjin, was infected with a strain of Covid-19 also found on pork imported from North America that he had handled, according to local authorities. Discovering traces of the coronavirus in ice cream prompts new questions, given that the food is usually consumed directly when cold, according to Han Jie, an environmental science professor from China’s Xian Jiaotong University. “The contamination of ice cream raw materials is different to the contamination that has happened previously during cold-chain food transportation and retail,” she said in an emailed response. “Frozen foods are usually safe to eat after being treated with high temperatures, such as cooking. But ice cream would not be treated with high temperatures. Whether the virus can infect people through the digestive tract if it enters the body via food, as far as I know there is no conclusive evidence yet.” Are fears over catching coronavirus from frozen food justified? Han was the co-author of a review published in the journal Environmental Chemistry Letters in October that looked at the available evidence at the time on whether Covid-19 could be transmitted through food and identified areas needing further research. “The continuous low-temperature environment kept through the storage and transport of refrigerated and frozen foods can dramatically prolong the survival of Sars-CoV-2, a characteristic commonly observed on other coronaviruses,” the review said. “The frequent detection of Sars-CoV-2 in frozen foods suggests that these are not random, isolated incidents but rather signs that viral contamination and food-borne transmission may present a systematic risk in the ongoing pandemic.” Previous research showed the coronavirus survived longer at 4 degrees Celsius (39 degrees Fahrenheit) than at higher temperatures. Other coronaviruses, including the one causing severe acute respiratory syndrome (Sars), were found to survive at 4 degrees Celsius for 14 to 49 days, depending on the material they were stored in, but research specifically on the survival of Sars-CoV-2 on food surfaces was lacking, the review said. Fears over the ice cream and other food have become a political matter, with Chinese experts and media suggesting the coronavirus could have been brought to China via frozen products, despite there being no evidence to support this theory. WHO experts this month arrived in China to begin their long-awaited investigation into the possible origins of the virus. Instances of food being found to be contaminated with the virus have been rare. China’s National Centre for Food Safety Risk Assessment has said random inspections yielded positive tests just 0.48 times per 10,000 samples. Of the 873,475 frozen food samples randomly inspected by Chinese customs, only 13 returned positive results for the coronavirus, according to the agency. To try to prevent contaminated food causing infections, China has stepped up tracing capabilities. A data-sharing platform is being tested to share information with restaurants on the processing, retail and sale status of over 90 per cent of the country’s imported frozen food, according to China’s market regulator. China has encouraged food producers to maintain records to aid traceability in the event of food safety incidents.