This article provides a detailed overview of research evaluating the persistence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; previously known as the 2019 novel coronavirus, 2019-nCoV) on surfaces and inanimate objects, which indicates that the virus could remain infectious for as little as a few hours to up to 9 days. This article also discusses potential methods of decontamination.
Since the start of the coronavirus outbreak in Wuhan, China, over 4.3 million cases of the virus have been reprted with approximately 300,000 deaths. According to the World Health Organization, as of March, infection by the virus was found to have a mortality rate of approximately 3.4%.
Given the relatively efficient transmission dynamics of the virus, which has been transmitted in the United States by community spread, understanding how the virus survives outside of the human body may provide important insights for halting the spread of this disease. This approach to preventing infection, focused on disinfecting potentially contaminated surfaces to reduce transmission of the virus, is particularly relevant due to the lack of proven therapies.
Update 5 April 2020: A recent publication in The New England Journal of Medicine titled “Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1” directly evaluated the stability of SARS-CoV-2, the virus that causes COVID-19, on various surfaces and in aerosols. The researchers found that the virus can remain viable in detectable quantities on plastic and stainless steel for up to 72 hours, on cardboard for up to 24 hours, and on copper for up to 4 hours.
The virus was detectable in the air for at least 3 hours following aerosolization. The quantity of virus particles was found to decay exponentially both on surfaces and in the air, with a median half-life of 1.1 hours in aerosols, 5.6 hours on stainless steel, and 6.8 hours on plastic.
However, a meta-analysis of research evaluating the persistence of viruses in the same family as SARS-CoV-2 suggests that SARS-CoV-2 could persist on surfaces for much longer, for up to 9 days.
Definitive insight into the persistence and infectivity of the SARS-2-CoV virus should require additional studies evaluating a wider range of conditions and strains. It is possible that the strain of virus studied in the New England Journal of Medicine publication has different characteristics than other strains that are currently circulating globally.
Original Article: In a publication in the Journal of Hospital Infection, researchers suggest that the SARS-CoV- 2 coronavirus may remain infectious for up to 9 days outside of the human body on inanimate surfaces, and that particular biocidal agents may be effective for deactivating the virus before transmission occurs, offering opportunities for potential interventions in healthcare and other settings.
Researchers from Bochum and Greifswald, Germany, recently published a review of available data on the longevity of coronaviruses on inanimate surfaces outside of the human body, and also the potential effectiveness of frequently used disinfectants for clearing potential contamination.
The scientists analyzed data from 22 studies in the scientific literature related to the human coronaviruses Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) and the veterinary coronaviruses mouse hepatitis virus (MHV), transmissible gastroenteritis virus (TGEV), and canine coronavirus (CCV).
After reviewing the longevity of coronavirus strains on metal, wood, glass, plastic, surgical gloves, disposable gowns, and other materials, Kampf et al found that, in general, the duration of coronavirus persistence is reduced at higher temperatures but extended at lower temperatures and that the quantity of virus particles on the surface is directly associated with the length of persistence in a strain-dependent manner.
While SARS-CoV (strain GVU6109) at a particular concentration was found to persist on a disposable gown at room temperature for only 1 hour, a higher concentration of the virus could last for 2 days. Although TGEV was shown to persist on steel for 4-96 hours at 40 degrees celsius, the virus could last for longer than 28 days at 4 degrees celsius. In other words, coronaviruses tend to live longer when present on surfaces at higher concentrations and in environments with lower temperatures.
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Common disinfectants including ethanol-based cleansers were shown to be effective for inactivating coronaviruses. After being exposed to solutions containing 78% to 95% ethanol for 30 seconds, a greater than 10,000-times reduction in the infectivity of the SARS coronavirus was observed.
The publication also provided information on the efficacy of cleansers containing hydrogen peroxide, 2-propanol, benzalkonium chloride, and chlorhexidine digluconate, among other agents. While the effectiveness of the biocidal agents appeared to depend upon the coronavirus strain, length of exposure, and other factors, in general, the ethanol-based solutions showed greater efficacy for inactivating coronaviruses than chlorhexidine-based solutions.
Of note, the researchers highlighted the relevance of human behavior to self-inoculation with the virus from contaminated surfaces. Referencing an observational study which showed that students, on average, touch their face with their own hands 23 times per hour, the scientists emphasized that the coronavirus can be transmitted in this manner from contaminated dry surfaces to mucous membranes of the nose, eyes, or mouth, and lead to infection.
Accordingly, the researchers noted the WHO recommendation that individuals “ ensure that environmental cleaning and disinfection procedures are followed consistently and correctly. Thoroughly cleaning environmental surfaces with water and detergent and applying commonly used hospital-level disinfectants (such as sodium hypochlorite) are effective and sufficient procedures.”
This is particularly relevant to healthcare settings where frequently-touched objects and surfaces in highly trafficked areas could contribute to the spread of the virus. Research evaluating the incidence of the SARS coronavirus on hospital surfaces found that, even after the implementation of preventative measures, multiple locations including the computer mouses at nursing stations and the public elevator handrail tested positive for the virus by RT-PCR.
Given that 21% of SARS cases worldwide were among healthcare workers during the 2003 epidemic, introducing better methods for regulating the spread of coronaviruses in healthcare settings is important for ensuring that patients can be effectively treated and that the spread of disease can be well-controlled.
The researchers also emphasized the importance of handwashing after contact with potentially contaminated surfaces or infected patients. “The WHO recommends to preferably apply alcohol-based hand rubs for the decontamination of hands, e.g. after removing gloves. Two WHO recommended formulations (based on 80% ethanol or 75% 2-propanol) have been evaluated in suspension tests against SARS-CoV and MERS-CoV, and both were described to be very effective,” Kampf et al stated.
While high levels of adherence to best-practice hand-washing may be difficult to achieve, these measures are nevertheless important for countering the spread of disease, particularly in healthcare settings. “In Taiwan, however, it was described that installing hand wash stations in the emergency department was the only infection control measure which was significantly associated with the protection from healthcare workers from acquiring the SARS-CoV, indicating that hand hygiene can have a protective effect.”
The authors concluded by stating that “human coronaviruses can remain infectious on inanimate surfaces for up to 9 days” and that, since disinfection of contaminated surfaces with 62–71% ethanol or 0.1% sodium hypochlorite for 1 minute was shown to significantly reduce the infectivity of other coronaviruses, these agents may also work against the 2019-nCoV.
Other research groups describing the persistence and infectivity of coronaviruses outside of the human body have emphasized the potential variability between strains. A review article published in 2015 noted that the SARS and MERS coronaviruses seem to survive on dry surfaces better than other human coronaviruses (229E, NL63, and OC43), with the MERS coronavirus demonstrating longer survival than other human coronaviruses.
The researchers also described the direct association between virus dose and survival time, noting that both the SARS-CoV and H3N2 influenza viruses persist longer on surfaces when the concentration of virus particles is increased. Some coronaviruses may live longer than others on surfaces outside of the human body, and are favored to live longer when a higher dose of virus is applied to a surface.
The medium transmitting the virus onto a dry surface could also influence the duration of infectivity. The researchers noted that, in a study evaluating the survival of influenza on bank notes, the addition of mucus could extend the survival time from hours to up to 17 days. Thus, the data from prior research studies investigating the survival of the coronavirus should be re-considered in the context of real-world materials, such as mucus, that could extend the survival time of the virus to a duration longer than that observed under the controlled conditions of the research laboratory.
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Overall, the researchers noted, “in all studies that tested varying temperature and relative humidity, lower temperature and relative humidity favoured the survival of both coronaviruses and influenza.” Interestingly, this could predict the limited spread of the novel coronavirus to tropical areas. Indeed, tropical Asian countries with a high temperature and relative humidity, including Malaysia, Indonesia, and Thailand, did not experience major outbreaks of the SARS coronavirus.
Additional methods of decontamination, including heating and ultraviolet (UV) irradiation, may also be helpful for containing the spread of the 2019-nCoV. Researchers from the Chinese Center for Disease Control and Prevention in Beijing found that the SARS coronavirus strain CoV-P9 could be rendered non-infectious after exposure to 56 degrees celsius for 90 minutes, 67 degrees celsius for 60 minutes, 75 degrees celsius for 30 minutes, or UV irradiation for 60 minutes.
While heating and irradiation was found to effectively decontaminate surfaces of the virus, the researchers nevertheless emphasized that the “survival ability of SARS coronavirus in human specimens and in environments seems to be relatively strong.”
Addressing the question, “how long do coronaviruses live on a surface” is not straightforward due to the variability between coronaviruses. Indeed, while the survival characteristics of the 2019 novel coronavirus and its susceptibility to common disinfectants have been evaluated scientifically, these characteristics may vary by strain and a more physically durable strain of the virus could evolve.
van Doremalen N, Bushmaker T, Morris DH, et al. (2020) Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. The New England Journal of Medicine. DOI: 10.1056/NEJMc2004973
Kampf G, Todt D, Pfaender S, Steinmann E. (2020) Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. The Journal of Hospital Infection, 104(3), 246-251. DOI: https://doi.org/10.1016/j.jhin.2020.01.022
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