A new study posted on BioRxiv found that SARS-CoV-2, the virus responsible for Covid-19, can survive on frozen meat and fish for periods up to 3 weeks, as researchers continue to explore the possibility that contaminated food could be the source of new outbreaks in countries which had previously controlled the virus.
The study noted the presence of infectious (live) virus, not just genetic material, on meat which was previously refrigerated and frozen for up to 3 weeks—and later thawed. This study comes on the heels of another recent report from Shenzen, China which found SARS- CoV-2 genetic material, not live virus capable of replication, on the surface of frozen chicken wings, a story recently covered by fellow Forbes contributor, Bruce Lee.
Needless to say, as Lee emphasizes, finding genetic material on the surface of food is not the same as finding live replicating virus. This distinction is important because viruses are quite different than bacteria—they cannot survive on their own without a live host. Besides, having even enough virus is even more crucial to risk of infection. As a result, the potential for infectivity—possessing a high enough viral load which is then capable of transmission to a person—after eating the particular food is quite remote.
In fact, another recent report by Reuters also found the presence of viral genetic material on the outer packaging of frozen seafood in Yantai, China. Thus far, there is no need to be overly concerned, as health officials in Shenzen or Yantai have yet to find any credible threat from these food-borne sources. And rightfully so, since the main mode of transmission of SARS-CoV-2 is droplet-spread, person-to-person, and not by surfaces or even fomites. Even the possibility of aerosolization of fomites (virus on surfaces) while offered, is still quite remote and does not constitute the primary mode of transmission.
For the new study, the researchers inoculated 500 tiny individual cubes of salmon, chicken and pork from supermarkets in Singapore with a hefty dose of SARS-CoV-2 viral particles. The meat was then stored at 3 different temperatures: 40C, (refrigeration) -200C, and -800C. After the meat was thawed at various time points (1, 2, 5, 7, 14 and 21 days after inoculation), the researchers determined that the amount of infectious virus—virus capable of reproducing—remained the same whether the temperature was 40C, -200C or -800C. The amount of infectious virus remained the same at 3 weeks in both refrigerated (40C) and frozen samples (-200C and -800C).
The authors of the new study hypothesize that workers in meat processing plants could potentially be a vector for spread of the virus, following exposure to the infected meat that that was previously frozen in other countries. This, the authors explain, could serve as an explanation for recent outbreaks in places like New Zealand that had no reports of new cases (to suggest community transmission) for over 3 months. That said, the contribution from poor working conditions (crowding, poor ventilation, lack of PPE, and shouting due to elevated ambient noise levels) along with contact with other infected workers who report to work—may also be responsible for spread of the virus.
In light of the new information obtained from the study, people should still realize that the risk of catching the virus from exposure to, or eating previously refrigerated or frozen meat and fish is theoretical at best. It’s a hypothesis that the authors have advanced, without definitive evidence of transmission at this point in time.
While the authors of the study have demonstrated that the virus can “survive the time and temperatures associated with transportation and storage conditions associated with the international food trade,” the potential for contamination of food with infectious virus may be possible. However it does not establish that this is may be a mode of possible transmission of Covid-19.
It does, however, argue that efforts to reduce the risk of Covid-19 outbreaks “seeded by contaminated food must begin at the source; that is food processing premises,” as the authors state. And, of course this should include meticulous attention to hand hygiene, cleaning of utensils, material and food contact surfaces.
The CDC has stated that “currently there is no evidence to suggest that handling food or consuming food is associated with Covid-19.” Moreover, the WHO has also issued a statement on food safety and handling explaining that “it is highly unlikely that people can contract Covid-19 from food or food packaging.”
Even if you were to consume food containing infectious virus, the acidity of your stomach would likely kill the virus instantly, making it a non-issue in terms of infectious spread within your body. And the chance of the virus gaining access to your nasal passages and upper airway while eating—the mode by which SARS-CoV-2 establishes an infection via the ACE2 receptor—is even more remote.