Since the beginning of the COVID-19 pandemic, people around the world have eaten billions of meals and, despite significant rates of infection throughout food processing, handling, distribution, and retailing facilities, there appears to be no conclusive evidence that the disease has been transmitted from the source of infection via the food supply chain.
There has been considerable discussion in Japan about the connection between food and the potential risk of SARS-CoV-2 transmission through food and the potential implications for food safety. The context for this has been the Japanese media reporting on news that Chinese regulatory authorities have detected the virus on frozen food products and speculation that an employee infection cluster in a Japanese food factory was caused by food contact. Recent announcements from China seem to indicate that this mode of transmission may have contributed to the global pandemic. Because China is one of Japan’s closest neighbors and exports foods to the country, these allegations cannot be ignored.
Furthermore, a recent increase in norovirus cases in Japan attributed to food has added to concerns about viral transmission via food. The norovirus season is generally observed from early autumn to mid-winter, but outbreaks have occurred in spring and summer. While norovirus and SARS-COV-2 are both viruses, they are very different in structure and in how they are affected in different environments. For example, alcohol does not adversely affect norovirus, but is effective for disinfection and as a countermeasure against COVID-19. It is imperative to understand the relationship between COVID-19 and food and to clarify how that coronavirus differs from norovirus.
Viruses usually remain viable and stable at cooler temperatures, even at a domestic refrigerator temperature of approximately 4℃. They are not inactivated, remaining viable for months. They do not lose their infectivity even at -70℃.
One report indicates that COVID-19 is able to maintain viability and will remain infective for between four and 21 days at 4℃. Therefore, it is not improbable to see reports that the virus was detected on frozen products. There are reports that COVID-19 has been isolated on chicken meat from Brazil and on shrimp from Ecuador.
Viral Infection from Food
There are two proposed routes for viral infection from food. In the first route, it is theorized that COVID-19 adheres to the surface of food, food containers, and packaging and is released through handling, allowing the virus to enter the body via the mucous membranes of the mouth, nose, and eyes. The second route involves COVID-19 that is present on or in food products that are consumed and the theory says this causes infection through the epithelial cells of the digestive tract and thereby proliferates. Neither of these routes have yet been verified.
Experiments with coronavirus attached to various materials in the laboratory have shown that the virus retains its infectivity on the surface of objects for quite some time. COVID-19
has been compared with the severe acute respiratory syndrome (SARS) virus that prevailed in 2002 and the Middle East respiratory syndrome (MERS) first reported in 2012, and it is thought that it will have a similar lifespan (see Table 1).
However, in reality, food does not appear to be a significant or likely path to infection with SARS-CoV-2. Experts at the World Health Organization have emphasized that China has sampled very large volumes of food packaging but found very few positive samples. In addition, there have been questions regarding the test methods employed by the Chinese researchers.