Imported cold chain food and packaging in many places tested positive for nucleic acid. What is the problem?

According to the announcement from Wuxi Liangxi: On January 21, the Liangxi District Center for Disease Control and Prevention of Wuxi City found that the inner surface of a batch of imported cherries (production date: 2020.12.18) tested positive for nucleic acid during routine monitoring of imported food.

According to Modern Express: At 16:55 on January 22, during the routine testing of imported food, Suzhou Industrial Park found that the nucleic acid test of the outer packaging of "frozen pork neck bones" imported by a food company was positive.

This year, positive nucleic acid tests on imported foods have been found in many places in China, which has brought great pressure and challenges to epidemic prevention and control, and has also attracted great attention from consumers.

So, why has imported food become a high-risk point for the epidemic? Where does the new coronavirus on the surface of food or its packaging come from? What are my country's requirements for imported food safety testing? How can we further strengthen control measures in the next step? How can we avoid contact infection during shopping? On January 23, Science and Technology Daily interviewed relevant experts.

There are many factors that may cause food to be contaminated by the new coronavirus

"Imported food has become an important source of food for Chinese consumers. my country is currently the world's largest import market for food and agricultural products." Dr. Li Yingchao, leader of the safe food major at the School of Inspection and Testing of Changzhou Engineering Vocational and Technical College, introduced that according to customs data, my country's total imports of various types of meat in 2019 were 4.841 million tons, and the import volume of aquatic products was 6.265 million tons. Affected by the epidemic this year, in order to ensure market supply and stabilize prices, my country's imported meat has continued to grow rapidly.

"Food, especially fresh and frozen products such as meat and aquatic products, are likely to be contaminated in every link from production to processing, packaging, storage, transportation to sales if the surrounding environment is contaminated by the new coronavirus, or if the employees themselves are infected with the new coronavirus," said Professor Yang Zhenquan, a food safety expert in catering services at the State Food and Drug Administration and professor at Yangzhou University.

Yang Zhenquan introduced that, generally speaking, the lower the temperature, the longer the virus can survive. The low temperature environment created by the cold chain provides a good living space for the virus. The COVID-19 virus is resistant to low temperatures. The surface temperature of frozen food and the low temperature of cold storage environment are suitable for the virus to survive for a long time. If it is contaminated in the high-incidence areas of the COVID-19 epidemic or in various circulation links, it is very easy to bring the virus to non-epidemic areas through cold chain transportation and cause the spread of the epidemic.

"If the new coronavirus exists in the food processing, transportation, circulation, and sales environment (air, personnel, production equipment, etc.), the food may carry the new coronavirus due to cross-contamination or secondary contamination." Yang Zhenquan said, for example, if people in the processing, transportation, and distribution links are infected with the new coronavirus, the virus may be transmitted through contact with utensils or even through droplets and aerosols floating and settling on the surface of food during breathing, causing viral contamination.

Experts believe that the amount of imported cold chain food entering the country every day is huge, with many types and batches. Due to many factors, it is not easy to test all of them. Viruses are omnipresent. There are potential risks in each link of the food packaging, inner packaging and food itself. It is impossible to detect all viruses through random inspections. Therefore, we must attach great importance to the potential safety risks of imported food and its cold chain logistics links.

Samples that tested positive

It does not necessarily mean that it has transmission activity

"Currently, all positive samples of the new coronavirus found on the surface of food or food packaging are from imported food, especially cold chain food. This is closely related to the current severe epidemic situation abroad and the fact that the new coronavirus can survive longer under low temperature conditions." Li Yingchao said.

"However, it should be emphasized that a sample that tests positive using the most widely used PCR nucleic acid detection technology does not necessarily mean that it has transmissible activity." Li Yingchao said that the presence of nucleic acid fragments can only mean that the sample is contaminated with the new coronavirus, and whether the virus is biologically active, that is, transmissible, requires further microbial culture technology to confirm. Previously, Chen Junshi, an academician of the Chinese Academy of Engineering and a researcher at the National Food Safety Risk Assessment Center, said that no live virus has been isolated and cultured from positive samples on the surface of food.

Yang Zhenquan told reporters that existing research and prevention and control practices have shown that COVID-19 is not a foodborne disease, and no cases of infection through food ingestion have been found. At present, all localities have stepped up control measures such as investigation, disinfection, testing, and screening. "The exposed problematic goods account for a small proportion of the overall goods, and the viral nucleic acid load is also low. As long as strict testing, disinfection and other protective measures are taken, there is no need to stay away from cold chain foods. Moreover, the detection result does not necessarily mean that it is contagious." Yang Zhenquan said.

Yang Zhenquan believes that nucleic acid positivity and virus survival are not the same thing. The premise for transmission from animals to humans is that the virus is contagious. The virus is composed of a protein shell and a long chain of nucleic acid. If the shell is destroyed, the virus loses its infectivity, but the nucleic acid test can still be positive.

In Li Yingchao's opinion, although imported frozen foods are occasionally tested positive for COVID-19, the actual situation shows that the probability of frozen foods testing positive for COVID-19 nucleic acid is extremely low. At present, a complete suspension of imported food would be a case of throwing the baby out with the bathwater. Strengthening the supervision of imported food is fundamental, and it is also a major challenge and training opportunity for my country's food safety supervision system.

my country has established a supervision and prevention system for imported cold chain food

Li Yingchao introduced that on November 9, 2020, the Office of the Joint Prevention and Control Mechanism of the State Council for the COVID-19 Epidemic issued the "Work Plan for Preventive and Comprehensive Disinfection of Imported Cold Chain Foods" to the whole country. The plan requires the realization of closed-loop control and traceability of the entire process to minimize the risk of the introduction of the new coronavirus through imported cold chain foods.

"The Work Plan for Preventive Comprehensive Disinfection of Imported Cold Chain Foods makes careful arrangements for the preventive comprehensive disinfection of imported cold chain foods, and puts forward specific requirements for the full-process closed-loop control and traceability of imported cold chain foods." Yang Zhenquan said that according to the plan, after completing the new coronavirus testing and sampling work, the relevant departments must, in accordance with the division of responsibilities, strictly implement preventive comprehensive disinfection at all links before the imported cold chain food comes into contact with people in our country for the first time, block the possible transmission chain of the virus by moving the checkpoints forward, and control the risk to the lowest level.

Li Yingchao told reporters that in early December 2020, the national imported cold chain food traceability management platform was completed and put into operation, basically realizing the information-based traceability of the entire chain from customs entry to production and processing, wholesale and retail, and catering services, and played an important role in online investigation, precise control, and on-site disposal. Subsequently, various provinces and cities also issued relevant management regulations to strengthen the supervision of imported food, especially cold chain food for the new coronavirus, and continue to pay attention to high-risk products from key countries and regions.

It is worth mentioning that in response to the recent problems with imported food, the General Administration of Customs has strengthened source control, taken measures such as moving checkpoints forward, conducting remote video inspections, and suspending product imports, further tightening port inspection and quarantine, and implementing all-round risk monitoring. For the relevant companies found to have problems, according to the risk level, measures such as suspending their registration qualifications in China, suspending the import of related products, and returning and destroying the temporarily detained goods have been taken, and resolutely refusing to bring "poisonous" goods into the customs.
Multiple measures to reduce infection risks

The reporter learned that the COVID-19 prevention and control plan requires all localities to implement daily protection, health monitoring and active nucleic acid screening for cold chain food-related practitioners to improve the sanitary conditions of the production, processing and trading environment and reduce the risk of infection for practitioners. In addition, according to the "Notice of the Ministry of Transport on Further Strengthening the Prevention and Control of COVID-19 in Cold Chain Logistics Channels" (Jiaoyun Mingdian [2020] No. 241), a technical guide for the prevention and control of COVID-19 and disinfection of cold chain food logistics imported by road and water has been formulated for road and water import cold chain food logistics companies and key logistics links.

"The Chinese Center for Disease Control and Prevention requires that industry practitioners who often come into close contact with cold chain products that have a high possibility of being contaminated by the new coronavirus, such as those engaged in loading and unloading, processing, and sales of cold chain products, need to enhance their awareness of protection, do a good job of daily protection, and avoid direct skin contact with cold chain products that may be contaminated; they need to wash and disinfect their hands immediately after completing work, and undergo nucleic acid screening regularly." Yang Zhenquan said.

Experts have pointed out that the COVID-19 epidemic is still spreading around the world. During the epidemic, we must first strengthen the sanitation, disinfection and closed management of all links in the food industry chain, require import and export companies to improve production, processing and trading conditions, and implement various normalized epidemic prevention and control measures in detail. Secondly, quarantine and regulatory departments should strengthen quarantine, increase sampling, improve detection methods, conduct timely detection and publish detection results. In short, it is necessary to strengthen the inspection, quarantine and disinfection of imported food, especially cold chain food, to effectively prevent the virus from entering the country through international logistics.

Consumers should protect themselves

For consumers, it is often impossible to determine whether the food they buy contains viruses. How can they protect themselves? Yang Zhenquan said, "Consumers should abide by five basic requirements in all aspects of purchasing, cooking, and eating: keep clean, separate raw and cooked food, cook thoroughly, keep food at a safe temperature, and use safe water and raw ingredients, etc."

Experts put forward the following specific suggestions:

When consumers purchase various imported foods, especially various imported animal products, they must choose regular markets and supermarkets and check whether they have been disinfected, tested and inspected, and whether they have nucleic acid test reports, inspection and quarantine marks and relevant disinfection certificates.

Do not buy imported food of unknown origin. If you buy fresh products through online shopping channels, the express packaging must be disinfected before it can be unpacked and brought indoors. The packaging must be properly collected and disposed of and must not be discarded at will.

After touching the outer packaging and fresh food, you should also wash your hands promptly to avoid touching your mouth, nose, eyes, etc. with dirty hands to minimize the risk.

When processing raw meat, aquatic products and other fresh and frozen foods, they must be cleaned carefully to prevent splashing. Raw and cooked foods must be handled separately, including the containers, cutting boards, knives, etc. that need to be prepared and used separately to avoid cross contamination.

After cooking, thoroughly wash and disinfect your hands, countertops, containers, kitchen utensils, etc. When cooking food, make sure it is cooked thoroughly.

During the entire process of washing, processing and cooking food, avoid touching your mouth, eyes, nose, etc. with dirty hands.

During the epidemic, try not to eat cold food, do not go to live poultry markets and pet markets, and avoid contact with wild animals.

We should develop good hygiene habits in our daily lives, wash our hands frequently, ventilate the room frequently, wear masks, use public chopsticks, cut our nails frequently, avoid crowding, reduce unnecessary gatherings and dinners, and actively advocate a healthy and civilized lifestyle.

◎ Science and Technology Daily reporter Guo Guozhong, correspondents Zhang Xuehua, Zhang Yun, Jiang Wenrong

Source: Science and Technology Daily. All images in this article are from Guangzhou Daily except those marked.

Editor: Liu Yiyang

Review: Julie

Final judge: Leng Wensheng