Surveillance of SARS-CoV-2 Contamination in Frozen Food-Related Samples — China, July 2020 – July 2021

INTRODUCTION: Current evidence shows that coronavirus disease 2019 (COVID-19) is neither a food safety issue nor a foodborne disease. However, the outbreaks of this disease in workers of meat- or poultry-processing plants and food markets have been reported in many countries. Systematic reports on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contamination in food-related samples worldwide are lacking so far. This study aimed to survey and monitor SARS-CoV-2 contamination in samples of foods or their packaging, storage environment, and employees, as well as explore the possible potential for virus transmission via frozen foods. METHODS: Swabs of frozen food-related samples were collected between July 2020 and July 2021 in 31 provincial-level administrative divisions (PLADs) and Xinjiang Construction Corps in China. The SARS-CoV-2 RNAs were extracted and analyzed by real-time quantitative polymerase chain reaction using the commercially available SARS-CoV-2 nucleic acid test kit. RESULTS: More than 55.83 million samples were analyzed, and 1,455 (0.26 per 10,000) were found to be positive for SARS-CoV-2 nucleic acid. Among the virus-positive samples, 96.41% (1,398/1,450) and 3.59% (52/1,450) were food/food packaging materials and environment, respectively. As for 1,398 SARS-CoV-2-positive food and food packaging materials, 99.50%, (1,391/1,398) were imported and 7 were domestic. The outer packaging of food was frequently contaminated by the virus 78.75% ( 1,101/1,398). CONCLUSIONS: Our study supported speculation that cold-chain foods might act as the SARS-CoV-2 carrier, and food handlers/operators were at high risk of exposure to the virus. It is necessary to carry out a comprehensive mass testing for SARS-CoV-2 nuclei acid, along with contact tracing and symptom screening in cold-chain food handlers and processors so as to identify high proportions of asymptomatic or pre-symptomatic infections. Meanwhile, research and development of effective self-protection equipment available at a temperature below −18 ℃ is urgent.