Summary
HCoV-19 (SARS-2) has caused more than 88,000 reported illnesses with a current case fatality rate of ~2%.
Here, we investigated the stability of viable HCoV-19 on surfaces and aerosols compared to SARS35 CoV-1.
Overall, stability is very similar between HCoV-19 and SARS-CoV-1.
We found that viable viruses could be detected :
|
HCoV-19 and SARS-CoV-1 exhibited similar half-lives in aerosols , with mean estimates of around 2.7 hours.
Both viruses show relatively long viability on stainless steel and polypropylene compared to copper or cardboard: the estimated median half-life for HCoV-19 is around 13 hours on steel and around 16 hours on polypropylene.
Our results indicate that aerosol and fomite transmission of HCoV-19 is plausible, as the virus can remain viable in aerosols for several hours and on surfaces for up to days.
Editor’s Note : AEROSOLS TRANSMISSION: Refers to the mixing of the virus with airborne droplets to form aerosols, which can float for long distances and cause infection after inhalation. The aqueous particle measures less than 5 microns, which establishes that it is capable of easily evaporating, AEROSOLIZING and remaining suspended for a prolonged period in the environment; In fact, it can dry out and remain like a dust particle and still be infective, depending on the type and virulence of the pathogen in question.
The measures in this case consist of using a single room or placing a cohort of individuals with the same agent in a closed room, with negative pressure; staff must wear a mask; In particular cases, such as SARS, respirators must be used, which are masks capable of filtering 95% of particles smaller than 5 microns in diameter; the patient must wear a mask when moving; and visits by susceptible people should be restricted.
What is a fomite? A fomite is any non-living object or substance that, if contaminated with a viable pathogen, such as bacteria, viruses, fungi or parasites, is capable of transferring said pathogen from one individual to another. That is why they are also called "passive vectors". |
A new human coronavirus now called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (previously called HCoV-19) emerged in Wuhan, China, in late 2019 and is now causing a pandemic.1 We analyzed the aerosol and Surface stability of SARS-CoV-2 and compared it to SARS-CoV-1, the most closely related human coronavirus.
We evaluated the stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces and estimated their decay rates using a Bayesian regression model.
The strains used were SARS-CoV-2 nCoV-WA1-2020 (MN985325.1) and SARS-CoV-1 Tor2 (AY274119.3).
Aerosols (<5 μm) containing SARS-CoV-2 (105.25 50% tissue culture infectious dose [TCID50] per milliliter) or SARS-CoV-1 (106.75-7.00 TCID50 per milliliter) were generated with the use of three Collison jet nebulizer and fed into a Goldberg drum to create an aerosol environment.
The inoculum resulted in cycle threshold values between 20 and 22, similar to those observed in samples obtained from the upper and lower respiratory tract in humans.
Our data consisted of 10 experimental conditions with two viruses (SARS-CoV-2 and SARS-CoV-1) in five environmental conditions (aerosols, plastic, stainless steel, copper, and cardboard). All experimental measurements are reported as means over three replicates.
Figure 1. Viability of SARS-CoV-1 and SARS-CoV-2 in aerosols and on various surfaces.
Estimated exponential decay rates and corresponding half-lives for HCoV-19 and SARS-CoV-1. Experimental conditions are ordered by the subsequent mean half-life for HCoV-19. A: Regression plots showing the predicted decline in virus titer over time; title plotted on a logarithmic scale. The dots show measured titers and are moved slightly along the time axis to avoid overplotting. The lines are random drawings of the joint posterior distribution of the exponential decay rate (negative of the slope) and intercept (initial virus titer), thus visualizing the range of possible decay patterns for each experimental condition.
SARS-CoV-2 remained viable in aerosols for the duration of our experiment (3 hours ), with a reduction in infectious titer from 103.5 to 102.7 TCID50 per liter of air. This reduction was similar to that observed with SARS-CoV-1, from 104.3 to 103.5 TCID50 per milliliter (Figure 1A).
SARS-CoV-2 was more stable on plastic and stainless steel than on copper and cardboard, and viable virus was detected up to 72 hours after application on these surfaces (Figure 1A), although the virus titer was significantly reduced ( from 103.7 to 100.6 TCID50 per milliliter of medium after 72 hours in plastic and from 103.7 to 100.6 TCID50 per milliliter after 48 hours in stainless steel).
The stability kinetics of SARS-CoV-1 were similar (from 103.4 to 100.7 TCID50 per milliliter after 72 hours in plastic and from 103.6 to 100.6 TCID50 per milliliter after 48 hours in stainless steel).
In copper , no viable SARS-CoV-2 was measured after 4 hours and no viable SARS-CoV-1 was measured after 8 hours.
On cardboard , viable SARS-CoV-2 was not measured after 24 hours and viable SARS-CoV-1 was not measured after 8 hours (Figure 1A).
Both viruses had an exponential decrease in virus titer under all experimental conditions, as indicated by a linear decrease in log10TCID50 per liter of air or milliliter of medium over time (Figure 1B).
The half-life of SARS-CoV-2 and SARS-CoV-1 was similar in aerosols , with mean estimates of approximately 1.1 to 1.2 hours and 95% credible intervals of 0.64 to 2.64 for SARS-CoV-2 and 0.78 to 2.43 for SARS-CoV-1.
The half-life of the two viruses was also similar on copper .
On cardboard , the half-life of SARS-CoV-2 was longer than that of SARS-CoV-1.
The longest viability of both viruses was on stainless steel and plastic; The estimated half-life of SARS-CoV-2 was approximately 5.6 hours in stainless steel and 6.8 hours in plastic (Figure 1C). The estimated differences in the half-life of the two viruses were small, except for cardboard (Figure 1C).
Data from individual replicates were noticeably “noisier” (i.e., there was more variation in the experiment, resulting in a larger standard error) for cardboard than for other surfaces (Fig. S1 to S5), so we recommend Caution when interpreting this result.
We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested. This indicates that differences in the epidemiological characteristics of these viruses likely arise from other factors, including high viral loads in the upper respiratory tract and the possibility that people infected with SARS-CoV-2 shed and transmit the virus while asymptomatic. . Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, as the virus can remain viable and infectious in aerosols for hours and on surfaces for up to days (depending on inoculum shed). These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and superspreading events, 5 and provide information for pandemic mitigation efforts. |
Appendix
HCoV-19 has caused many more cases of illness and resulted in more deaths than SARS-CoV-1 and is proving more difficult to contain. Our results indicate that the higher transmissibility observed for HCoV-19 is unlikely to be due to greater environmental viability of this virus compared to SARS-CoV-1.
Instead, there are a number of potential factors that could explain the epidemiological differences between the two viruses. There have been early indications that people infected with HCoV-19 can shed and transmit the virus while pre-symptomatic or asymptomatic . This reduces the effectiveness of quarantine and contact tracing as control measures in relation to SARS-CoV-1.
Other factors that may play an important role include the infectious dose required to establish an infection, the stability of the virus in the mucus, and environmental factors such as temperature and relative humidity.
In ongoing experiments, we are studying the viability of the virus in different matrices, such as nasal secretion, sputum and fecal matter, and at the same time variable environmental conditions, such as temperature and relative humidity.
The epidemiology of SARS-CoV-1 was dominated by nosocomial transmission and SARS-CoV1 was detected on a variety of surfaces and objects in healthcare settings. Transmission of HCoV-19 also occurs in hospital settings, with more than 3,000 reported cases of hospital-acquired infections. These cases highlight the vulnerability of healthcare settings to the introduction and spread of HCoV-19.
However, in contrast to SARS-CoV-1, most secondary transmission has been reported outside healthcare settings and widespread transmission in the community is being seen in various settings, such as homes, places of work and group meetings.
A notable feature of SARS-CoV-1 was super-spreading events , in which a single infected individual was responsible for a large number of secondary cases, well above the average number denoted by the reproduction number.
The trend toward such super-spreading events has two important consequences for the epidemiology of emerging infections: it makes any introduction of infection more likely to disappear by chance, but when outbreaks occur they are explosive and can overwhelm hospitals and healthcare capacity. public.
A number of hypothetical super spread events have been reported for HCoV-19. Given that SARS-CoV-1 superspreading events have been linked to aerosol and fomite transmission, our finding that HCoV-19 has viability in the environment comparable to that of SARS-150 CoV-1 lends credence to we hypothesize that it may also be associated with superlearning.
