Surrogates of SARS-CoV-2* – a lipid-enveloped RNA bacteriophage (Phi6) and two animal coronaviruses (CoV; MHV and TGEV**) – survived cold storage temperatures for 30 days, study finds , highlighting the risk of viral disease surviving on food products and potential transmission to humans during consumption.
“As enveloped viruses such as SARS-CoV-2 and others [CoVs can] survive refrigeration and freezing for long periods of time, there is a potential risk of viral persistence on contaminated food products which could lead to further exposure and transmission,” the researchers said. “[Hence,] a better understanding of the survival of these viruses at low temperatures on meat and fish products, as well as other foods, is needed and should be encouraged.
“[Our study showed that] viral surrogates differed in terms of survival, depending on the food item and temperature, but overall the viruses survived for [the full 30-day period] at high concentrations at both refrigerated (4°C) and frozen (–20°C) temperatures,” the researchers said.
At refrigerated temperature, 30 day logten reductions were largest for MHV (5.7, 5.6, 3.3 and 3.1 MPN IU/100 mL for chicken, pork, beef and salmon, respectively) followed by Phi6 (4 .7, 4.8, 1.3 and 3.5 PFU/100 mL, respectively). The least reduced viral strain was TGEV (1.1, 0.7, 0.9 and 1.4 MPN IU/100 ml). [Appl Environ Microbiol 2022;doi:10.1128/aem.00504-22]
MHV always had the largest 30-day logten reductions in all frozen samples (6.8, 5.9, 5.3 and 3.7 MPN IU/100 mL for chicken, pork, beef and salmon, respectively). Reductions were somewhat similar between Phi6 (1.8, 0.42, 0.52, and 2.03 PFU/100 mL, respectively) and TGEV (2.3, 1.5, 1.5, and 1.7 MPN IU/100mL).
“[There were] generally greater reductions at chilled temperature than at frozen temperature,” the researchers said, suggesting that the substitutes persisted in colder conditions.
The results on Phi6 align with data showing the ability of Phi6 to remain on food surfaces for up to 60 days at both tested temperatures.
“[The] The reductions in TGEV were not significantly different at either temperature on any of the foods tested, indicating that this virus is reduced in similar proportions between the two temperatures and in all four food items. explained the researchers. Have a low diaryten the reductions for both temperatures imply that TGEV may remain on food surfaces for long periods in cold storage.
Besides temperature, virus recovery methods and biological properties of surrogates might have influenced the differences in results, they noted. Although virus surface hydrophobicity and assessed food surfaces were not characterized in the assay, these may also have taken into account differences in survival. [www.who.int/publications/i/item/covid-19-and-food-safety-guidance-for-food-businesses, accessed August 7, 2022]
An important and worrying finding
“We provide evidence that surrogates of SARS-CoV-2 survive for relatively long and variable periods on refrigerated and frozen meat and fish, potentially due to the low temperatures that allow the virus to survive,” the researchers said. researchers. “[This] is an important and worrying finding.
“While you can’t keep meat in the fridge for 30 days, you can keep it in the freezer for just as long,” pointed out first author, assistant professor Emily Bailey of Campbell University, Buies Creek, North Carolina, United States, in a press release.
As such, rigorous and sustainable food sanitation, from harvest to distribution, is warranted to prevent contamination, they stressed. “[T]there is a need to better respond to the lack or inadequate disinfection of these foods before meat packaging.
Despite evidence showing the ability of these surrogates to survive in different environmental conditions, their use in place of the actual SARS-CoV-2 may have limited results, the researchers noted. [Environ Sci Technol 2017:51:8692-8700;
Environ Sci Technol Lett 2020;7:544-553; Environ Sci Technol 2021:55:2674-2683;
Appl Environ Microbiol 2021;87:e0153221] “[T]The differences in virus survival observed in our results suggest that an indicator virus may not be predictive of pathogenic SARS-CoV-2 behavior.
Further studies should therefore look at other viruses, including SARS-CoV-2 itself and other human and animal CoVs, to assess their ability to survive on various meat and fish products and even in fresh produce.