Fresh and frozen foods can hold SARS-CoV-2 for at least 21 days.

In some parts of the world, a new outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has occurred after weeks or months when it has completely stopped. Some examples are the recent local events in Vietnam, New Zealand and Beijing. Recent research published on Preprint Server bioRxiv* In August 2020, foodborne contamination could underlie these outbreaks, suggesting that this route of transmission should not be overlooked to contain the pandemic.

Xinfadi, Beijing

Approximately two months after the zero new cases, a cluster of SARS-CoV-2 infected patients was detected in the Beijing Xinfadi wholesale market. This was officially due to contaminated food imported from outside the region. In response, steps have been taken to prevent other outbreaks in China. But the world is largely ignorant because it is unaware of such risks.

Reason for new occurrence

Unrecognized subclinical SARS-CoV-2 can cause new outbreaks and continue to infect the community. Another mechanism is that the traveler could bring in the virus and then jump from host to new host. This means that asymptomatic infected travelers were either tested as false negatives or were found to have been infected and violated quarantine rules. This can lead to occult SARS-CoV-2 infection.

However, researchers have calculated that this is a unlikely scenario. The probability that 20 generations of virus will pass undetected is only 1/1000 even if the number of reproductions is 1, and continuous transmission and detection continue. 1 in 20 infectious diseases. In these situations, occult infections are unlikely to be the cause of recent outbreaks.

Food related infection clusters

A third possibility is that contaminated food shipped between regions carries the SARS-CoV-2 virus. This is reliable given that many SARS-CoV-2 infected clusters occur in meat and seafood processing plants around the world. Examples include poultry processing plants in the UK, ready-to-eat meat production facilities in the UK, tuna canning stations in Portugal and Ghana, and abattoirs in Australia and Germany. In fact, in the last case, more than 1,500 workers were SARS-CoV-2 positive at a large slaughterhouse in Gutersloh, Germany. The series of infections resulted in blockades in two districts with more than 600,000 inhabitants.

Thus, the issue of the origin of relapse seems to revolve around food processing plants where contaminated foods are imported, transferring infections to locals and spreading new viral chain seeds. The SARS-CoV-2 virus was found on workers in the Xinfadi market and on cutting boards from which salmon imported from the outside was sliced.

Authorities responded by picking up millions of swabs from market workers, people staying close to the market, and other components of Beijing’s food supply chain. This detected 335 cases of SARS-CoV-2 infection. Ecuadorian shrimp were also detected to be virus positive.

After that, salmon from Europe was banned, as well as from facilities later confirmed to have SARS-CoV-2. This includes the United States, Germany and Brazil. Ecuadorian shrimp have also been suspended.

Confirmation of infectious virus in frozen meat

Previous studies reported that detectable SARS-CoV-2 on copper, cardboard, stainless steel/plastic surfaces at temperatures of 21-23 °C was not tested after 4 and 24 hours. , Many scientists suspected this route, and 3 days. Therefore, the authors of the current study looked at how long the virus could survive in frozen or chilled meat and salmon for three weeks. This allowed us to test the possibility of a new outbreak inoculated with imported food containing live virus.

21 days infectious virus quantification. Viral titers were determined by limiting dilution. Titers are expressed as mean ± SD log10 TCID50 / mL. SARS-CoV-2 was stored alone or in the presence of fish, chicken and pork and tested under refrigeration (4 °C). Freeze (-20°C and -80°C).

They tested a 500 mm3 salmon, chicken, pork cube purchased from a Singapore supermarket and added the virus at a dose of 3 x 10 in 200 μl.⁶ TCID50 / ml. These were stored at 4°C, -20°C and -80°C. Then we tested the virus after 1, 2, 5, 7, 14, and 21 days. They found that the virus titer remained at the same level at all three temperatures and that all samples remained infectious.

In line with today’s general thinking, the World Health Organization advises that the spread of COVID-19 in foodborne or food packaging is unlikely. “It’s not a major route of transmission, but the potential for contaminated items to travel to areas without COVID-19 and cause an outbreak is an important hypothesis,” the researchers say. Therefore, it is essential to assess the risk of such foodborne infections surviving the transport and storage processes involved in import trade.

Meat trading and COVID-19

High rates of infection between workers in slaughterhouses and slaughterhouses indicate crowded workplaces, high noise levels that require screaming, lack of adequate ventilation, as evidenced by an increasing number of infected clusters. It may indicate a risk factor. Meat is processed manually, while automated lines usually process salmon. When salmon are also handled manually, there is a risk of contamination.

Such workers, who are generally from lower economies, may continue to work after being infected, increasing the risk of catching the virus and transmitting it to crowded homes. They also travel by public transport, which is usually crowded.

The fact that most surfaces in such facilities are likely to be stainless steel, the low temperature, and lack of sunlight, including UV light, supports a longer lifespan of the virus. Therefore, all environmental and individual factors make meat and fish susceptible to contamination during handling and subsequent processing of raw meat.

The butchers are usually at standard or room temperature, but the researchers say that meat is kept at temperatures below 12°C.^ofC is chopped and meat is stored at 3-7°C according to food regulations.

Implication

This study shows that all types of meat used daily, chicken, pork, and salmon, can carry infectious viruses through transportation, storage, and conditions associated with the import and export of these foods. is showing. In particular, the temperatures tested cover standard refrigerated and standard frozen temperatures. As regulated by law, the absence of conditions such as drying and temperature changes is beneficial for virus survival. And, in fact, it could not detect a decrease in virus titer, indicating a loss of infectivity.

Therefore, they believe, “Contaminated imported foods can transmit viruses to workers and the environment. Infected food handlers can be an index case for new outbreaks.” “

Given the sheer volume of international food trade, it is quite possible that an unusual epidemic event could occur and cause an outbreak if the viral epidemic had previously been eradicated. To prevent such occurrences, food hygiene should be initiated at the factory, including repeated rigorous cleaning of hands, work surfaces and other food contact surfaces, materials and cookware.

The condition of the worker should be inspected. Staff must be trained, encouraged to be absent in case of illness, and checked. Such workers’ leaves should be encouraged to promote the safety of workers and consumers. The use of personal protective equipment should be examined until habits are established, but social distances should always be taught and encouraged.

The import market requires regular cleaning of hands, utensils, and surfaces to prevent contamination of other foods. Consumers should be instructed to wash their hands after touching raw food and properly cook the food to destroy the virus.

Current investigations and other reports of virus detection in imported frozen chicken and shrimp packaging materials suggest that food regulations may set guidelines related to this new situation that may not help avoid old standards. It should serve as a warning to authorities and public health authorities “non-traditional food safety risks”.

*Important Notices

bioRxiv It publishes preliminary, non-peer reviewed scientific reports and should not be considered conclusive and should not guide clinical practice/health-related behavior or be treated as established information.