Management of Ebola Virus Disease: Is Environmental Decontamination Effective?

To the Editor—The West African Ebola virus (EBOV) disease (EVD) outbreak was the most extensive and devastating EVD outbreak in history. Effective case management is a key component of EVD control, involving the care of infectious patients in an environment that limits ongoing transmission. We read with interest the recent article by Poliquin et al [1], which adds information on Ebola viral contamination of clinical settings where patients with EVD were managed. The authors cite a prior study by Bausch et al [2], conducted in Uganda, as the only previous study in this area. However, we are aware of 3 other studies examining environmental contamination of EVD clinical facilities [3-5]. Given how important this issue is for the safety of health workers and patients, we would like to highlight this other relevant evidence.

Our group performed an audit of environmental decontamination practice at Connaught Hospital’s Ebola holding unit (EHU), also in Freetown, Sierra Leone, conducted in January 2015 (Youkee et al [3]). We sampled extensively in a clinical area (EVD holding unit ward–EHU) where patients with EVD were managed, collecting 173 swab samples for evidence of EBOV RNA by RT-PCR analysis, using ∑-Virocult™ swabs. Sample collection was temporally related to EHU decontamination, after an EVD-positive patient was transferred out to the EVD Treatment Centre and before admission of a new patient with suspected EVD. We sampled the clinical environment immediately after the departure of patients with EVD from the bedside before cleaning, and then 30 and 60 minutes after routine decontamination with 0.5% chlorine solution, according to our protocols, to assess the efficacy of decontamination procedures and the effect of time on EBOV RNA persistence. We repeated the process after a period of refresher training for hygiene staff.

Our results showed EBOV RNA contamination of the immediate patient bedside area and of visibly soiled sites and equipment, before decontamination. There was no evidence of contamination of environmental surfaces outside the patient’s direct contact area in the ward. We demonstrated that routine decontamination procedures reduced evidence of EBOV RNA contamination at 30 and 60 minutes after decontamination, in all but a few locations. The bed frame and floor near the bed were areas where routine decontamination did not consistently remove EBOV RNA. Similarly, Poliquin et al [1] reported that bedrails, which were not visibly soiled, and concrete floors were areas of EBOV RNA persistence.

In a report from Italy by Puro et al [4], swab samples from the floor under the bed and table of a patient with EVD were positive for EBOV RNA by RT-PCR, after routine cleaning. This was an area that had been heavily contaminated with body fluids. Repeated sampling after more extensive cleaning yielded negative results, and Vero cell culture of the PCR-positive sample was negative. A study at Jui-SL China Friendship Hospital, in Sierra Leone, found no RT-PCR evidence of EBOV RNA in swab samples taken from the clinical area around a convalescent patient with EVD [5].

Together, these data inform the important debate on the potential risk to patients of admission to EVD clinical areas. In many EVD clinical care facilities, patients who had suspected (not confirmed) EVD were managed alongside other patients with suspected or confirmed EVD [6]. This was largely unavoidable during the West African EVD outbreak, owing to the large number of suspected cases, delayed diagnostic confirmation, and a shortage of beds in the treatment center, but this situation raised significant concern about nosocomial transmission—that patients with suspected EVD who were not actually infected could be exposed to EBOV during their admission [6, 7]. Our EHU, like others, was divided into high- and low-risk areas, with individual bed spaces. Staff movement was unidirectional from low- to high-risk areas, with decontamination between individual patient contact episodes. Regular and vigilant personal and environmental decontamination, together with patient supervision to avoid physical interaction between patients, was used to minimize the risk of nosocomial transmission [6].

Our audit results reassured us that there was a low risk of EVD transmission to patients within that environment from fomites or from contact with clinical staff. We conclude that the floor area and bedrails in the immediate vicinity of a patient’s bed require extra attention during cleaning. We await the results of epidemiological studies looking at nosocomial transmission inside EHUs, which are also critical to this debate.