Evidence Briefs

Provide a synthesis of the best available evidence on a variety of priority topic areas as identified by leading infectious disease experts. We systematically explore the published literature using a comprehensive search strategy to identify relevant research on infection prevention, management, and control. For more information on our search strategy of the published literature, click here.
McMaster University
NCCMT

Decontamination and virus inactivation

Mar 28, 2017

Author(s): Stephanie Vendetti-Hastie, RN, CIC, Kristin Read, MPH, & Dr. Maureen Dobbins, PhD, RN
Expert Reviewer(s): Dr. Mark Loeb, MD, MSc, FRCPC & Dr. Dominik Mertz, MD, MSc

The OutbreakHelp Evidence Briefs aim to provide short summaries of the available evidence related to priority topic areas identified by leading infectious disease experts. Content for the Evidence Briefs were developed using a comprehensive and systematic search of the academic literature from inception to December 31st 2015 (more recently published information on this topic may be available here). All results were screened for relevance using pre-defined inclusion and exclusion criteria. Included articles must have met the following criteria: 1) specific to the topic of Ebola Virus Disease (EVD), 2) human research or research with real-world applicability, 3) study in a peer reviewed journal, and 4) published in either English or French. Articles identified as relevant were tagged with priority topic areas and assessed for quality using abbreviated versions of appropriate critical appraisal tools; a 5-star rating scheme was applied to articles as relevant. Relevance screening, category tagging, and critical appraisal were independently conducted by two raters and conflicts were resolved through discussion. A thematic analysis was performed on included articles by charting and then categorizing common concepts and topics discussed in the literature. Results are summarized in a narrative. The following Evidence Brief discusses environmental considerations focusing specifically on EVD decontamination and virus inactivation. 


Main Message

EVD is inactivated by a variety of currently recommended disinfectant agents such as sodium hypochlorite 0.5% and ethanol 67% at contact times of 5 and 10 minutes. Technologies such as nanoemulsions have also reported inactivation properties, though are not readily available or currently not recommended for use.

Virus that has been shed and is suspended in secretions and excretions containing organic and cellular debris may be protected from environmental decontamination procedures if not routinely cleaned and manually removed prior to decontamination.

Decontamination and virus inactivation

Within the literature a variety of physical and chemical methods to decontaminate the environment and inactivate microorganisms have been described and play an important role in preventing and controlling the spread of infection in healthcare settings.

Youkee, et al. (2015) conducted an assessment of the effectiveness of routine decontamination procedures inside an EVD holding unit in Sierra Leone during a period of time when confirmed EVD positive patients were being cared for. Three sets of viral swabs were collected at 15 pre-determined locations around the bedside of a positive patient. For each set of swabs, initial sample collection took place immediately after discharge of the EVD patient (T0), after which the area was cleaned with 0.5% sodium hypochlorite cleaning solution using routine cleaning procedures.  Swabs were again collected 30 (T30) and 60 minutes (T60) after environmental decontamination. Results had been compared before (swab sets 1 and 2) and after a rapid educational intervention (swab set 3). In addition, an extended panel of swabs was collected within the clinical area and in surrounding areas. Study results indicate 16 samples from T0, T30, and T60 were reverse transcription polymerase chain reaction (RT-PCR) positive out of a total of 173 swabs collected. All positive samples were located around the immediate patient bedside. The mattress, which showed visible body fluid contamination was the only item positive at T0 for each swab set. Swab set 1 found 3 out of 43 swabs tested had RT-PCR positive results at T0 for the latrine, mattress, and dirty glove #2. The middle of the bedframe was RT-PCR positive at T30 but not at T0. Swab set 2 had RT-PCR positive results in five locations out of 46 swabs tested at T0. Swabs of the bedframe and middle of the floor remained positive at T60. The floor at the head of the bed and bedside table were positive at T60 but not at T0. Swab set 3 (after the educational intervention) had 2 positive results out of 43 swabs tested at T0, but no positive results at T30 or T60 suggesting that education of cleaning staff may increase effectiveness of cleaning, however, sample sizes were small to draw any final conclusions (Youkee, et al., 2015).

Sagripanti and Lytle (2011) performed an experimental study to determine the inactivation kinetics UV exposure (UVC, 254 nm radiation) of Zaire Ebola virus (ZEBOV) that had been dried on glass. Virus samples were exposed to UV radiation emitted by lamps for selected times up to 30 seconds. After the UV exposures, virus inactivation was measured. Study results indicate ZEBOV is sensitive to UVC radiation, however survival rates may relate to the environmental conditions surrounding the dried virus particles. The presence of significant amounts of dried protein from serum and cellular debris from the growth medium in the study provided some protection from inactivation by UV radiation. This protected virus population had a four and six-fold lower UVC sensitivity than the general virus population (Sagripanti & Lytle, 2011).

Cook et al. (2015) examined virus inactivation using sodium hypochlorite at 0.1%, 0.5%, and 1% concentrations on steel carriers. The 0.5% and 1% sodium hypochlorite solutions performed similarly with viable virus recoverable at 1 minute contact time with the solution, while all carriers used were sterile following a five minute contact time. Efficiency of virus disinfection correlated positively with the concentration of solution and length of contact time with higher concentrations of sodium hypochlorite at longer contact times achieving greater disinfection. Similar findings were reported when using 67% ethanol as a disinfecting agent, with virus inactivation on 3 of 9 samples after one minute and no recoverable virus found after 5 and 10 minute contact times (Cook, et al., 2015).

Chepurnov et al. (2003) investigated the ability of a lipid-containing preparation (nanoemulsion) called ATB to inactivate ZEBOV in cell culture fluid and in blood from infected monkeys. Of particular interest was the ability of the nanoemulsion to inactivate ZEBOV either in a suspension or on surfaces (glass, plastic and stainless steel). Three concentrations of ATB were studied 10%, 1% and 0.1% respectively. Study results found that a 20 minute exposure to 10% ATB inactivated virus in both cell culture and blood and a 1% ATB concentration deactivated only the virus in culture at 20 minutes. In blood, an inactivation of 96% occurred after 24 hours of exposure at this concentration due to the presence of larger amounts of proteins (erythrocyte debris) in the preparation, causing additional consumption of ATB. The 0.1% concentration displayed a low efficacy on both preparations (40-60% reduction after 24 hour exposure). In some cases, an insignificant increase in virus level was observed 1H after exposure. ATB at concentrations of 1 and 10% displayed a good disinfecting ability on surfaces. Exposures of 20 min and 1 hour showed similar results with a more than 4.0 log decrease achieving complete eradication of the virus on these surfaces with no differences observed by type of surface material (Cherpurnov, et al., 2003).

Smither et al. (2015) performed a study designed to inactivate the EVD (Kitwit) in clinical specimens prior to running diagnostic tests and to assess the impact of the inactivation methods on lab test results.  EBOV inactivation efficacy was evaluated within serum of infected marmosets and spiked mouse blood samples using a Buffer AVL reagent, a common laboratory reagent that contains chaotropic salt. They also evaluated EVD inactivation efficacies of 96% ethanol and heat (60°C for 15 min). Overall, neither Buffer AVL nor heat alone consistently inactivated the virus under the conditions tested. The combination of Buffer AVL plus heat consistently inactivated the virus as did buffer AVL plus ethanol (but not ethanol alone). Positive PCR results were obtained on all samples after different inactivation treatments indicating that although the samples had been rendered safer to handle, -presumably dead- virus was still detectable using PCR (Smither, et al., 2015).

Mitchell & McCormick (1984) examined the effect of various methods for the inactivation of the Mayinga strain of the Ebola virus (EBOV) in human blood specimens on various laboratory tests such as glucose, electrolytes, enzymes, and coagulation factors. Three inactivation methods were utilized: chemical inactivation using 3% acetic acid (pH 2.5) for 15 minutes, gamma radiation (1.27 x 106 rads) using a 60Co gamma cell, and thermal heating in a 60°C water bath for 1 hour. In preliminary experiments, serum was heated at 45, 56, and 60°C for periods of up to 75 minutes. Complete inactivation occurred only at 60°C. The time required to inactivate 5 logs plaque-forming unit (PFU)/mL of Ebola virus in serum was 37 minutes. After a 15 minutes exposure to 3% acetic acid EBOV in blood was inactivated. While these methods achieved virus inactivation they would adversely alter some lab test results and would be unsuitable for samples that were to be tested for certain enzyme levels and coagulation factors (Mitchell & McCormick, 1984).

Conclusion

There is little available research in the area of decontamination and virus inactivation. The studies reported here have several limitations including differing methodologies, small sample sizes, and various specimen types, as well as, potential inconsistencies with sampling techniques, delays in sample processing and potential inadequacies with detection limits of testing assays. These limitations may bias results and limit the applicability of findings. The main limitation in the context of this brief is that any reduction in the sensitivity of the tests may result in false conclusions that one or the other decontamination procedure is superior to another. Furthermore, it is unknown whether EBOV positive samples by PCR testing contain replication competent virus, and it remains unclear how PCR results relates to transmission potential.

References

Chepurnov, A. A., Bakulina, L. F., Dadaeva, A. A., Ustinova, E. N., Chepurnova, T. S., Baker, J. R. (2003). Inactivation of Ebola virus with a surfactant nanoemulsion. Acta Tropica87(3), 315-320. [OutbreakHelp Star Rating: 3]

Cook, B. W., Cutts, T. A., Nikiforuk, A. M., Poliquin, P. G., Strong, J. E., & Theriault, S. S. (2015). Evaluating environmental persistence and disinfection of the ebola virus makona variant. Viruses7(4), 1975-1986. [OutbreakHelp Star Rating: 5]

Mitchell, S.W., McCormick, J.B. (1984). Physicochemical inactivation of Lassa, Ebola, and Marburg viruses and effect on clinical laboratory analyses. Journal of Clinical Microbiology, 20(3), 486-489. [OutbreakHelp Star Rating: 3]

Sagripanti, J.L., Lytle, C.D. (2011). Sensitivity to ultraviolet radiation of Lassa, vaccinia, and Ebola viruses dried on surfaces. Archives of Virology, 156(3), 489-494. [OutbreakHelp Star Rating: 4.5]

Smither, S. J., Weller, S. A., Phelps, A., Eastaugh, L., Ngugi, S., O'Brien, L. M., Steward, J., Lonsdale, S.G., Lever, M. S. (2015). Buffer AVL alone does not inactivate Ebola virus in a representative clinical sample type. Journal of clinical microbiology53(10), 3148-3154. [OutbreakHelp Star Rating: 5]

Youkee, D., Brown, C. S., Lilburn, P., Shetty, N., Brooks, T., Simpson, A., Bentley, N., Lado, M., Kamara, T.B., Walker, N.F., Johnson, O. (2015). Assessment of environmental contamination and environmental decontamination practices within an Ebola holding unit, Freetown, Sierra Leone. PLOS ONE10(12), e0145167. [OutbreakHelp Star Rating: 4.5]