COVID-19 might be able to travel on food, preliminary study results indicate

A new study exploring the potential that COVID-19 can linger on food, including frozen seafood, draws connections between recent outbreaks of the disease in China, Vietnam, and New Zealand.

The study, “Seeding of outbreaks of COVID-19 by contaminated fresh and frozen food,” was filed on preprint server BioRxiv on 17 August. BioRxiv publishes preliminary findings that have not been scrutinized by peer review.

“An explanation is required for the re-emergence of COVID-19 outbreaks in regions with apparent local eradication. Recent outbreaks have emerged in Vietnam, New Zealand, and parts of China where there had been no cases for some months. Importation of contaminated food and food packaging is a feasible source for such outbreaks and a source of clusters within existing outbreaks,” according to the study’s abstract.

In June, traces of the coronavirus were discovered on fish chopping boards in Beijing’s Xinfadi seafood market, which had become the epicenter of a new cluster of COVID-19 infections. And in July,  the General Directorate of Chinese Customs announced the blocking of three Ecuadorian shrimp companies from exporting to the country. According to reports from Chinese health authorities, samples taken from one of the internal walls of a container transporting Ecuadorian shrimp tested positive for COVID-19, as well as on the outer surface of five boxes from these companies.

In New Zealand, some of the infections in a recent outbreak were traced back to the Americold cold storage facility in Auckland, the country’s capital. And Vietnam, a country that had won praise for its aggressive measures in containing the virus, has suffered scores of infections and 10 deaths in August.

The study’s researchers, from Singapore and Ireland, said their lab work shows the novel coronavirus can endure the time and temperatures associated with transportation and storage conditions for international food trade, according to a Fox News report.

Transmission of COVID-19 on food – deemed a “non-traditional” theory of transmission – was the focus of the study. It found that at 21–23 degrees Celsius, no viable SARS-CoV-2 remained after 4 hours on copper surfaces, 24 hours on cardboard, and after three days on stainless steel and plastic surfaces.

However, studying the survival of SARS-CoV-2 on refrigerated and frozen meat and salmon over three weeks, “there was no decline in infectious virus after 21 days at 4 degrees Celsius (standard refrigeration) and minus-20 degrees Celsius (standard freezing).”

“Our laboratory work has shown that SARS-CoV-2 can survive the time and temperatures associated with transportation and storage conditions associated with international food trade,” the study found.

The study counters a World Health Organization statement from 13 August that food or food packaging has not been linked to the transmission of COVID-19. Members of the administration of U.S. President Donald Trump and seafood trade groups in the United States and Europe have all released statements calling such a link “misinformation.”

However, the study’s authors posit that COVID-19 can potentially jump from contaminated seafood to a worker processing the product, who then can become a vector of the virus.

“We believe it is possible that contaminated imported food can transfer virus to workers as well as the environment. An infected food handler has the potential to become an index case of a new outbreak,” study authors wrote. "The international food market is massive and even a very unlikely event could be expected to occur from time to time."

The study’s authors urged more careful precautions against COVIDD-19 contamination in meat and seafood processing facilities.

“Our findings, coupled with the reports from China of SARS-CoV-2 being detected on imported frozen chicken and frozen shrimp packaging material, should alert food safety competent authorities and the food industry of a ‘new normal’ environment where this virus is posing a non-traditional food safety risk," the authors wrote.

Photo courtesy of Big Foot Productions