Chinese researchers claim imported frozen food packaging helped spread COVID-19
18 Jul 2022 --- Chinese researchers have linked almost 700 cases of COVID-19 to contaminated frozen food packaging, supporting speculation that cold-chain foods act as a pathway for SARS-CoV-2 and might present a risk of virus transmission between regions.
The findings, published in China CDC Weekly, contradict official World Health Organization (WHO) statements asserting that there is no evidence linking COVID-19 transmission between people through food packaging. This is the first time it has been proposed that environment-to-human transmission originated from contaminated imported food.
The study aimed to analyze and summarize COVID-19 outbreaks related to cold-chain foods to provide a scientific basis for tracing the epidemiological trajectory of the pandemic and provide risk assessments and mitigation policies.
Overall, 37 COVID-19 outbreaks and 5,741 infected cases were reported within the study period (June 2020 to July 15, 2021). It was found that seven outbreaks and 689 cases were linked to imported frozen foods. The first index case among the seven outbreaks was exposed to SARS-CoV-2-contaminated outer packaging of frozen food, triggering the subsequent community transmission.
Packaging virus outbreaks
In total, 368 people infected with SARS-CoV-2 were reported in Beijing in June 2020. These infected people are all directly or indirectly related to the Xinfadi Market – 169 people were market staff, and 103 people were visitors to the market less than 14 days before the symptoms appeared. The remaining 96 people were in close contact with these individuals, states the study.
The findings suggest frozen food packaging could be spreading the COVID-19 virus, contrary to common belief.No other early independent transmission chain beyond the market was found, indicating that Xinfadi Market was the unique source of the outbreak. Notably, five surface-swabbing samples collected from salmon in the original sealed package in the company’s cold storage, a unique imported food supplier of Xinfadi Market located outside the market, were positive for SARS-CoV-2.
The virus in the fish swab shared at least seven mutations with that of Xinfadi Market. After this, clusters of COVID-19 cases linked to cold-chain foods were frequently reported in China, say the study authors. The outbreak in Dalian, on July 22, 2020, was associated with imported cold-chain foods. The porter was first infected by having contact with the outer packaging of imported frozen cod contaminated with SARS-CoV-2.
The virus was subsequently introduced to a local seafood company through the infected porter’s wife and then spread further. However, active and infectious viruses were not successfully isolated from the samples of cold-chain food in Beijing and Dalian. Therefore, the role of SARS-CoV-2-contaminated cold-chain foods in the spread of the COVID-19 epidemic could not be confirmed.
Packaging politics
The researchers postulate that clusters of COVID-19 cases related to cold-chain foods in China suggest that SARS-CoV-2 can survive on the contaminated surface of foods and packaging materials and maintain infectivity for at least 11 months at a temperature of −18 C.
Although the virus genome sequences from the cold-chain foods were identical to those of the cases, the researchers also concede that there is still no direct evidence that the virus caused the local epidemic.
“Further studies are required to evaluate the presence and persistence of infectious SARS-CoV-2 and its RNA in frozen food compartments, sample conditions, and the intervention strategies for reducing the virus infection,” concludes the study.
By Louis Gore-Langton
