Effectiveness of Four Disinfectants against Ebola Virus on Different Materials

Infection prevention and control studies for care of patients with suspected or confirmed filovirus disease in healthcare settings, with focus on Ebola and Marburg: an integrative review

Objective

To review evidence pertaining to methods for preventing healthcare-associated filovirus infections (including the survivability of filoviruses in clinical environments and the chlorine concentration required for effective disinfection), and to assess protocols for determining the risk of health worker (HW) exposures to filoviruses.

Design

Integrative review.

Data sources

PubMed, Embase, Google Scholar, internet-based sources of international health organisations (eg, WHO, CDC), references of the included literature and grey literature.

Study selection

Laboratory science, clinical research and real-world observational studies identified through comprehensive search strings that pertained to Ebola disease and Marburg disease and the three research objectives.

Methods

Using the framework of population, intervention or exposure, outcomes, study types and report characteristics, reviewers extracted data and critically appraised the evidence using predefined data extraction forms and summary tables. The extraction forms, summary tables and critical appraisals varied based on the included literature; we used both the QUIPS Risk-of-Bias tool when possible and an internally developed instrument to systematically extract and review the evidence from observational and experimental studies. Evidence was then synthesised and summarised to create summary recommendations.

Results

Thirty-six studies (including duplicates across research questions) were included in our reviews. All studies that related to the review questions were either (1) descriptive, real-world studies (ie, environmental audits of various surfaces in operational Ebola Treatment Units) or (2) controlled, laboratory studies (ie, experimental studies on the survivability of ebolaviruses in controlled conditions), presenting a range of concerns pertaining to bias and external validity. Our reviews of viral survivability evidence revealed significant disconnections between laboratory-based and real-world findings. However, there is greater viral persistence in liquid than dried body fluids, with the possible exception of blood, and ebolaviruses can survive for significant periods of time in dried substrate. Evidence suggests that 0.5% hypochlorite solution should be used for disinfection activity. Spills should be cleaned with covering and soaking for 15 min. Existing literature suggests that within a well-resourced clinical environment with trained, foreign HWs and established protocols, transmission of ebolaviruses as an occupational risk is a rare event. Despite the high rates of HW infections within public African healthcare settings, no evidence with low risk of bias exists to assess the risk of various occupational exposures given that all high-quality studies were conducted on foreign Ebola clinicians who had low overall rates of infection. This review underscores the critical need for better-quality evidence to inform best practices to ensure HW safety during filovirus disease epidemics.

The Biosafety Research Road Map: The Search for Evidence to Support Practices in the Laboratory-Crimean Congo Haemorrhagic Fever Virus and Lassa Virus

Introduction

Crimean Congo Hemorrhagic Fever (CCHF) virus and Lassa virus (LASV) are zoonotic agents regarded as high-consequence pathogens due to their high case fatality rates. CCHF virus is a vector-borne disease and is transmitted by tick bites. Lassa virus is spread via aerosolization of dried rat urine, ingesting infected rats, and direct contact with or consuming food and water contaminated with rat excreta.

Methods

The scientific literature for biosafety practices has been reviewed for both these two agents to assess the evidence base and biosafety-related knowledge gaps. The review focused on five main areas, including the route of inoculation/modes of transmission, infectious dose, laboratory-acquired infections, containment releases, and disinfection and decontamination strategies.

Results

There is a lack of data on the safe collection and handling procedures for tick specimens and the infectious dose from an infective tick bite for CCHF investigations. In addition, there are gaps in knowledge about gastrointestinal and contact infectious doses for Lassa virus, sample handling and transport procedures outside of infectious disease areas, and the contribution of asymptomatic carriers in viral circulation.

Conclusion

Due to the additional laboratory hazards posed by these two agents, the authors recommend developing protocols that work effectively and safely in highly specialized laboratories in non-endemic regions and a laboratory with limited resources in endemic areas.

Inactivation of the enveloped virus phi6 with hydrodynamic cavitation

The COVID -19 pandemic reminded us that we need better contingency plans to prevent the spread of infectious agents and the occurrence of epidemics or pandemics. Although the transmissibility of SARS-CoV-2 in water has not been confirmed, there are studies that have reported on the presence of infectious coronaviruses in water and wastewater samples. Since standard water treatments are not designed to eliminate viruses, it is of utmost importance to explore advanced treatment processes that can improve water treatment and help inactivate viruses when needed. This is the first study to investigate the effects of hydrodynamic cavitation on the inactivation of bacteriophage phi6, an enveloped virus used as a SARS-CoV-2 surrogate in many studies. In two series of experiments with increasing and constant sample temperature, virus reduction of up to 6.3 logs was achieved. Inactivation of phi6 at temperatures of 10 and 20 °C occurs predominantly by the mechanical effect of cavitation and results in a reduction of up to 4.5 logs. At 30 °C, the reduction increases to up to 6 logs, where the temperature-induced increased susceptibility of the viral lipid envelope makes the virus more prone to inactivation. Furthermore, the control experiments without cavitation showed that the increased temperature alone is not sufficient to cause inactivation, but that additional mechanical stress is still required. The RNA degradation results confirmed that virus inactivation was due to the disrupted lipid bilayer and not to RNA damage. Hydrodynamic cavitation, therefore, has the potential to inactivate current and potentially emerging enveloped pathogenic viruses in water at lower, environmentally relevant temperatures.

Aerosol Survival, Disinfection and Formalin Inactivation of Nipah Virus

Nipah virus is a relatively newly discovered emerging virus on the WHO list of priority pathogens which has the potential to cause outbreaks with high fatality rates. Whilst progress is being made in the development of animal models for evaluating vaccines and therapies, some of the more fundamental data on Nipah virus are lacking. We performed studies to generate novel information on the aerosol survival of Nipah virus and to look at the efficacy of two common disinfectants. We also performed studies to evaluate the inactivation of Nipah virus by using neutral buffered formalin. Nipah virus was relatively stable in a small particle (1–5 µm) aerosol in the dark, with it having a decay rate of 1.46%min⁻¹. Sodium hypochlorite (at 10%) and ethanol (at 80%) reduced the titre of Nipah virus to undetectable levels. Nipah virus that was in tissue culture medium was also inactivated after 24 h in the presence of 10% formalin.

Chlorine efficacy against bacteriophage Phi6, a surrogate for enveloped human viruses, on porous and non-porous surfaces at varying temperatures and humidity

While efficacy of chlorine against Phi6, a widely-used surrogate for pathogenic enveloped viruses, is well-documented, surfaces common to low-resource contexts are under-researched. We evaluated seven surfaces (stainless steel, plastic, nitrile, tarp, cloth, concrete, wood) and three environmental conditions-temperature (4, 25, 40 °C), relative humidity (RH) (23, 85%), and soiling-to determine Phi6 recoverability and the efficacy of disinfection with 0.5% NaOCl. Overall, Phi6 recovery was >4 log₁₀ PFU/mL on most surfaces after drying 1 hour at all temperature/humidity conditions. After disinfection, all non-porous test conditions (48/48) achieved ≥4 LRV at 1 and 5 minutes of exposure; significantly more non-porous surfaces met ≥4 LRV than porous (p < 0.001). Comparing porous surfaces, significantly fewer wood samples met ≥4 LRV than cloth (p < 0.001); no differences were observed between concrete and either wood (p = 0.083) or cloth (p = 0.087). Lastly, no differences were observed between soil and no-soil conditions for all surfaces (p = 0.712). This study highlights infectious Phi6 is recoverable across a range of surfaces and environmental conditions, and confirms the efficacy of chlorine disinfection. We recommend treating all surfaces with suspect contamination as potentially infectious, and disinfecting with 0.5% NaOCl for the minimum contact time required for the target enveloped virus (e.g. Ebola, SARS-CoV-2).

Estimating Risk of Introduction of Ebola Virus Disease from the Democratic Republic of Congo to Tanzania: A Qualitative Assessment

Between April 2018 and November 2020, the Democratic Republic of Congo (DRC) experienced its 11th Ebola virus disease (EVD) outbreak. Tanzania's cross-border interactions with DRC through regular visitors, traders, and refugees are of concern, given the potential for further spread to neighboring countries. This study aimed to estimate the risk of introducing EVD to Tanzania from DRC. National data for flights, boats, and car transport schedules from DRC to Tanzania covering the period of May 2018 to June 2019 were analyzed to describe population movement via land, port, and air travel and coupled with available surveillance data to model the risk of EVD entry. The land border crossing was considered the most frequently used means of travel and the most likely pathway of introducing EVD from DRC to Tanzania. High probabilities of introducing EVD from DRC to Tanzania through the assessed pathways were associated with the viability of the pathogen and low detection capacity at the ports of entry. This study provides important information regarding the elements contributing to the risk associated with the introduction of EBV in Tanzania. It also indicates that infected humans arriving via land are the most likely pathway of EBV entry, and therefore, mitigation strategies including land border surveillance should be strengthened.

Henipaviruses-A constant threat to livestock and humans

In this review, we highlight the risk to livestock and humans from infections with henipaviruses, which belong to the virus family Paramyxoviridae. We provide a comprehensive overview of documented outbreaks of Nipah and Hendra virus infections affecting livestock and humans and assess the burden on the economy and health systems. In an increasingly globalized and interconnected world, attention must be paid to emerging viruses and infectious diseases, as transmission routes can be rapid and worldwide.

Evaluation of the SARS-CoV-2 Inactivation Efficacy Associated With Buffers From Three Kits Used on High-Throughput RNA Extraction Platforms

Rapid and demonstrable inactivation of SARS-CoV-2 is crucial to ensure operator safety during high-throughput testing of clinical samples. The inactivation efficacy of SARS-CoV-2 was evaluated using commercially available lysis buffers from three viral RNA extraction kits used on two high-throughput (96-well) RNA extraction platforms (Qiagen QIAcube HT and the Thermo Fisher KingFisher Flex) in combination with thermal treatment. Buffer volumes and sample ratios were chosen for their optimised suitability for RNA extraction rather than inactivation efficacy and tested against a representative sample type: SARS-CoV-2 spiked into viral transport medium (VTM). A lysis buffer mix from the MagMAX Pathogen RNA/DNA kit (Thermo Fisher), used on the KingFisher Flex, which included guanidinium isothiocyanate (GITC), a detergent, and isopropanol, demonstrated a minimum inactivation efficacy of 1 × 10⁵ tissue culture infectious dose (TCID)₅₀/ml. Alternative lysis buffer mixes from the MagMAX Viral/Pathogen Nucleic Acid kit (Thermo Fisher) also used on the KingFisher Flex and from the QIAamp 96 Virus QIAcube HT Kit (Qiagen) used on the QIAcube HT (both of which contained GITC and a detergent) reduced titres by 1 × 10⁴ TCID₅₀/ml but did not completely inactivate the virus. Heat treatment alone (15 min, 68°C) did not completely inactivate the virus, demonstrating a reduction of 1 × 10³ TCID₅₀/ml. When inactivation methods included both heat treatment and addition of lysis buffer, all methods were shown to completely inactivate SARS-CoV-2 inactivation against the viral titres tested. Results are discussed in the context of the operation of a high-throughput diagnostic laboratory.

Investigative study into whether an insect repellent has virucidal activity against SARS-CoV-2

A small-scale study with Mosi-guard Natural spray, an insect repellent containing Citriodiol, was performed to determine if it has virucidal activity against SARS-CoV-2. A liquid test examined the activity of the insect repellent and the individual components for virucidal activity. A surface contact test looked at the activity of the insect repellent when impregnated on a latex surface as a synthetic skin for potential topical prophylactic application. Both Mosi-guard Natural spray and Citriodiol, as well as other components of the repellent, had virucidal activity in the liquid contact test. On a latex surface used to simulate treated skin, the titre of SARS-CoV-2 was less over time on the Mosi-guard Natural-treated surface but virus was still recovered.

A systematic review of chlorine-based surface disinfection efficacy to inform recommendations for low-resource outbreak settings

Background

Infectious diseases can be transmitted via fomites (contaminated surfaces/objects); disinfection can interrupt this transmission route. However, disinfection guidelines for low-resource outbreak settings are inconsistent and not evidence-based.

Methods

A systematic review of surface disinfection efficacy studies was conducted to inform low-resource outbreak guideline development. Due to variation in experimental procedures, outcomes were synthesized in a narrative summary focusing on chlorine-based disinfection against 7 pathogens with potential to produce outbreaks in low-resource settings (Mycobacterium tuberculosis, Vibrio cholerae, Salmonella spp., hepatitis A virus, rotavirus, norovirus, and Ebola virus).

Results

Data were extracted from 89 laboratory studies and made available, including 20 studies on relevant pathogens used in combination with surrogate data to determine minimum target concentration × time (“CT”) factors. Stainless steel (68%) and chlorine-based disinfectants (56%) were most commonly tested. No consistent trend was seen in the influence of chlorine concentration and exposure time on disinfection efficacy. Disinfectant application mode; soil load; and surface type were frequently identified as influential factors in included studies.

Conclusions

This review highlights that surface disinfection efficacy estimates are strongly influenced by each study's experimental conditions. We therefore recommend laboratory testing to be followed by field-based testing/monitoring to ensure effectiveness is achieved in situ.

Efficacy of microbicides for inactivation of Ebola-Makona virus on a non-porous surface: a targeted hygiene intervention for reducing virus spread

Microbicides play critical roles in infection prevention and control of Ebola virus by decontaminating high-touch environmental surfaces (HITES), interrupting the virus-HITES-hands nexus. We evaluated the efficacy of formulations containing different microbicidal actives for inactivating Ebola virus-Makona strain (EBOV/Mak) on stainless-steel carriers per ASTM E2197-11. Formulations of sodium hypochlorite (NaOCl) (0.05-1%), ethanol (70%), chloroxylenol (PCMX) (0.12-0.48% by weight) in hard water, and a ready-to-use disinfectant spray with 58% ethanol (EDS), were tested at contact times of 0, or 0.5 to 10 min at ambient temperature. EBOV/Mak was inactivated (> 6 log10) by 70% ethanol after contact times ≥ 2.5 min, by 0.5% and 1% NaOCl or EDS (> 4 log10) at contact times ≥ 5 min, and by 0.12-0.48% PCMX (> 4.2 log10) at contact times ≥ 5 min. Residual infectious virus in neutralized samples was assessed by passage on cells and evaluation for viral cytopathic effect. No infectious virus was detected in cells inoculated with EBOV/Mak exposed to NaOCl (0.5% or 1%), PCMX (0.12% to 0.48%), or EDS for ≥ 5 min. These results demonstrate ≥ 6 log10 inactivation of EBOV/Mak dried on prototypic surfaces by EDS or formulations of NaOCl (≥ 0.5%), PCMX (≥ 0.12%), or 70% ethanol at contact times ≥ 5 min.

Laboratory management of Crimean-Congo haemorrhagic fever virus infections: perspectives from two European networks

Background

Crimean-Congo haemorrhagic fever virus (CCHFV) is considered an emerging infectious disease threat in the European Union. Since 2000, the incidence and geographic range of confirmed CCHF cases have markedly increased, following changes in the distribution of its main vector, Hyalomma ticks.

Aims

To review scientific literature and collect experts’ opinion to analyse relevant aspects of the laboratory management of human CCHF cases and any exposed contacts, as well as identify areas for advancement of international collaborative preparedness and laboratory response plans.

Methods

We conducted a literature review on CCHF molecular diagnostics through an online search. Further, we obtained expert opinions on the key laboratory aspects of CCHF diagnosis. Consulted experts were members of two European projects, EMERGE (Efficient response to highly dangerous and emerging pathogens at EU level) and EVD-LabNet (Emerging Viral Diseases-Expert Laboratory Network).

Results

Consensus was reached on relevant and controversial aspects of CCHF disease with implications for laboratory management of human CCHF cases, including biosafety, diagnostic algorithm and advice to improve lab capabilities. Knowledge on the diffusion of CCHF can be obtained by promoting syndromic approach to infectious diseases diagnosis and by including CCHFV infection in the diagnostic algorithm of severe fevers of unknown origin.

Conclusion

No effective vaccine and/or therapeutics are available at present so outbreak response relies on rapid identification and appropriate infection control measures. Frontline hospitals and reference laboratories have a crucial role in the response to a CCHF outbreak, which should integrate laboratory, clinical and public health responses.