Stability of SARS-CoV-2 in cold-chain transportation environments and the efficacy of disinfection measures

Abstract

Background: Low temperature is conducive to the survival of COVID-19. Some studies suggest that cold-chain environment may prolong the survival of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and increase the risk of transmission. However, the effect of cold-chain environmental factors and packaging materials on SARS-CoV-2 stability remains unclear.

Methods: This study aimed to reveal cold-chain environmental factors that preserve the stability of SARS-CoV-2 and further explore effective disinfection measures for SARS-CoV-2 in the cold-chain environment. The decay rate of SARS-CoV-2 pseudovirus in the cold-chain environment, on various types of packaging material surfaces, i.e., polyethylene plastic, stainless steel, Teflon and cardboard, and in frozen seawater was investigated. The influence of visible light (wavelength 450 nm-780 nm) and airflow on the stability of SARS-CoV-2 pseudovirus at -18°C was subsequently assessed.

Results: Experimental data show that SARS-CoV-2 pseudovirus decayed more rapidly on porous cardboard surfaces than on nonporous surfaces, including polyethylene (PE) plastic, stainless steel, and Teflon. Compared with that at 25°C, the decay rate of SARS-CoV-2 pseudovirus was significantly lower at low temperatures. Seawater preserved viral stability both at -18°C and with repeated freeze-thaw cycles compared with that in deionized water. Visible light from light-emitting diode (LED) illumination and airflow at -18°C reduced SARS-CoV-2 pseudovirus stability.

Conclusion: Our studies indicate that temperature and seawater in the cold chain are risk factors for SARS-CoV-2 transmission, and LED visible light irradiation and increased airflow may be used as disinfection measures for SARS-CoV-2 in the cold-chain environment.

Keywords: LED visible light; SARS-CoV-2; airflow movement; cold-chain; decay rate analysis; disinfection method; low temperature; viral activity.

Figure 1

Identification of SARS-CoV-2 pseudovirus. (A) Structure analysis of lentivirus and SARS-CoV-2 pseudovirus using Transmission electron microscopy (TEM) assay. (B) Infectivity of SARS-CoV-2 pseudovirus on 293T-hACE-2 cells. (C) The protein expression of S-spike in lentivirus and SARS-CoV-2 pseudovirus, HIV Gag-p24 is a lentivirus capsid protein and also exists in pseudovirus. (D) Decay curves of SARS-CoV-2 pseudovirus over 3 days on the surface of Teflon film, cardboard, stainless steel, and PE plastic. The measurements were linearized premised on first-order decay, in which the natural log (ln)-transformed measured concentration at each time point was divided by the concentration at time zero. (E) Log10-transformed mean pseudovirus decay rate constants k of SARS-CoV-2 pseudovirus on the surfaces of different materials at 16°C. Scale bar: 100 nm (A) and 200 μm (B). *p<0.05.

Figure 2

The stability of SARS-CoV-2 pseudovirus under cold-chain temperatures. (A) The decay curves of SARS-CoV-2 pseudovirus on PE plastic over 20 days under different temperatures. (B) The decay rate constants k of SARS-CoV-2 pseudovirus on PE plastic under different temperatures. **p <0.01 compared with 25°C.

Figure 3

The protective effect of seawater on SARS-CoV-2 pseudovirus at -18°C. (A) The decay curves over time (days) of SARS-CoV-2 pseudovirus, which was solutes in seawater or deionized water, on PE plastic at -18°C or under freeze-thawing. The treatment condition is freezing and thawing once a day, and virus activity is tested once every two days. (B) Decay rate constants k of SARS-CoV-2 pseudovirus at -18°C and under the condition of freeze-thawing cycles. ns., no significantly difference; *p<0.05; ***p<0.001.

Figure 4

The disinfection potential of LED visible light from 450 nm to 780 nm on SARS-CoV-2 pseudovirus at -18°C. The decay curves over time (min) of SARS-CoV-2 pseudovirus on PE plastic (A) and cardboard at -18°C that expose or un-expose to LED visible light (450 nm ~ 780 nm). The decay rate constants k of LED visible light exposed SARS-CoV-2 pseudovirus on the PE plastic and cardboard (B) at -18°C were significantly higher than that of light non-exposed control. (C) Genomic RNAs of SARS-CoV-2 pseudovirus on the PE plastic that was exposed or unexposed to LED visible light at -18°C were determined by agarose gel electrophoresis, control: SARS-CoV-2 pseudovirus RNA without any treatment (D) The RNA band intensities were quantified analysis using gray-scale scanning software. ns, no significantly difference; **p<0.01.7.

Figure 5

The effect of airflow movement on the viability of SARS-CoV-2 pseudovirus at -18°C. The decay curves over 32 hours of SARS-CoV-2 pseudovirus on PE plastic and cardboard (A) at -18°C that was treated or untreated with the airflow movement (3 m/s). The decay rate constants k of wind-treated SARS-CoV-2 pseudovirus on the PE plastic (B) and cardboard at -18°C were significantly higher than that of non-airflow movement controls. *p<0.05; **p<0.01.

Figure 6

Stability of SARS-CoV-2 in cold-chain transportation environments and the efficacy of disinfection measures. Cold-chain temperature and salt were risk factors that could prolong SARS-CoV-2 viability. Laboratory studies suggested that LED visible light exposure and airflow movement could promote the inactivation of SARS-CoV-2 in the cold-chain environment.