Virus DNA left on a hospital bed rail was found in nearly half of all sites sampled across a ward within 10 hours and persisted for at least five days, according to a new study by UCL and Great Ormond Street Hospital (GOSH).
The study, published as a letter in the Journal of Hospital Infection, aimed to safely simulate how SARS-CoV-2, the virus that causes Covid-19, may spread across surfaces in a hospital.
Instead of using the SARS-CoV-2 virus, researchers artificially replicated a section of DNA from a plant-infecting virus, which cannot infect humans, and added it to a milliliter of water at a similar concentration to SARS-CoV-2 copies found in infected patients’ respiratory samples.
Researchers placed the water containing this DNA on the hand rail of a hospital bed in an isolation room – that is, a room for higher-risk or infected patients – and then sampled 44 sites across a hospital ward over the following five days.
They found that after 10 hours, the surrogate genetic material had spread to 41% of sites sampled across the hospital ward, from bed rails to door handles to arm rests in a waiting room to children’s toys and books in a play area.
This increased to 59% of sites after three days, falling to 41% on the fifth day.
Dr. Lena Ciric (UCL Civil, Environmental & Geomatic Engineering), a senior author of the study, said: “Our study shows the important role that surfaces play in the transmission of a virus and how critical it is to adhere to good hand hygiene and cleaning.
“Our surrogate was inoculated once to a single site, and was spread through the touching of surfaces by staff, patients and visitors. A person with SARS-CoV-2, though, will shed the virus on more than one site, through coughing, sneezing and touching surfaces.”
The highest proportion of sites that tested positive for the surrogate came from the immediate bedspace area -including a nearby room with several other beds – and clinical areas such as treatment rooms.
On day three, 86% of sampled sites in clinical areas tested positive, while on day four, 60% of sampled sites in the immediate bedspace area tested positive.
Co-author Dr. Elaine Cloutman-Green (UCL Civil, Environmental & Geomatic Engineering), Lead Healthcare Scientist at GOSH, said: “People can become infected with Covid-19 through respiratory droplets produced during coughing or sneezing.
Equally, if these droplets land on a surface, a person may become infected after coming into contact with the surface and then touching their eyes, nose or mouth.
“Like SARS-CoV-2, the surrogate we used for the study could be removed with a disinfectant wipe or by washing hands with soap and water. Cleaning and handwashing represent our first line of defense against the virus and this study is a significant reminder that healthcare workers and all visitors to a clinical setting can help stop its spread through strict hand hygiene, cleaning of surfaces, and proper use of personal protective equipment (PPE).”
SARS-CoV-2 will likely be spread within bodily fluid such as cough droplets, whereas the study used virus DNA in water. More sticky fluid such as mucus would likely spread more easily.
One caveat to the study is that, while it shows how quickly a virus can spread if left on a surface, it cannot determine how likely it is that a person would be infected.
In the ongoing COVID-19 pandemic caused by the novel coronavirus, SARS CoV-2, early isolation of hospitalized inpatients with suspected COVID-19 is important to reduce the likelihood of nosocomial spread. However, patients with COVID-19 may present with respiratory syndromes indistinguishable from those caused by common respiratory viruses [1].
This poses a challenge for early isolation and containment, especially during significant ongoing community transmission. While isolation ward beds are prioritized for suspected COVID-19 cases, unsuspected cases of COVID-19 without suspicious contact or travel history may initially be nursed outside of dedicated isolation wards prior to detection.
Given that patients outside the isolation ward may not be subject to movement restrictions and share common facilities, social mingling represents a potential route for nosocomial spread, especially as COVID-19 cases may present with mild symptoms and remain relatively well [1].
While social distancing has been identified as crucial for containment in the community [2], social distancing within hospitals is equally vital in reducing nosocomial spread, especially in hospitals where the majority of patients are nursed in multi-bedded cohort rooms, rather than in single-occupancy rooms.
In Singapore, a globalized Asian city-state, the first imported case of COVID-19 was reported at the end of January 2020; followed by the first case of local transmission in early February 2020 [3].
At our institution, the Singapore General Hospital (SGH), the isolation ward was reserved for confirmed/suspected cases of COVID-19. However, given rising numbers of locally transmitted cases, from 4th February, our institution placed individuals admitting with respiratory symptoms but without suspicious contact or travel history in respiratory surveillance wards (RSWs) where COVID-19 was first excluded and healthcare workers (HCWs) used full personal protective equipment (PPE) including N95 masks, disposable gowns, gloves and face-shields. Despite this resource-intensive containment effort, it was recognized that some cases of COVID-19 with mild symptoms might be initially admitted to the general ward.
Our institution therefore emphasized hospital-wide social distancing measures. For patients admitting to the RSW, as the risk of a potentially unsuspected case of COVID-19 was higher, patients were advised to avoid mingling and to wear surgical masks at all times; no visitors were allowed.
Additionally, infrastructural modifications were instituted to facilitate social distancing. In the RSWs, patients were nursed in cohort rooms with three patients to a room, spaced at least ∼2 m apart, and partitions were placed between patient beds (Figure 1 ).
In the general ward, shared communal facilities (e.g., day rooms) were closed during the duration of the ongoing COVID-19 outbreak, and patients were limited to one visitor at any time. HCWs in the general ward wore surgical masks.
Hospital-wide, in common areas such as waiting areas, pharmacies, food and retail outlets, patients were directed to keep 1 m apart from one another, using visual cues (e.g., floor markings and markings on seats) to guide waiting and queuing in both seated and standing areas.
Comparison of ward layout and social distancing measures employed in a general ward and a respiratory surveillance ward, during the COVID-19 outbreak.
Over a three-month period from 4th January to 4th April 2020, a total of 75 confirmed cases of COVID-19 were diagnosed in our institution. While the majority of cases (84.0%, 63/75) were admitted to isolation wards, 12 cases of COVID-19 were initially admitted outside of the isolation ward.
Of these, the majority (91.6%, 11/12) were admitted to the RSW. One patient was initially admitted to the general ward and nursed in a cohorted cubicle with five other patients, as respiratory symptoms were initially mild.
The patient was transferred to an RSW 19 h after admission, where the diagnosis of COVID-19 was made. At diagnosis, the cycle threshold (Ct) value for SARS-CoV-2 on reverse transcription-polymerase chain reaction (RT-PCR) testing of oropharyngeal swab samples was 18, an inverse surrogate for high viral load and potential infectivity; this was in keeping with data suggesting peak viral shedding in the first week of symptoms [4].
A total of 18 patients in the general ward and two patients in the RSW had shared a room or common toilet with the index case; all were deemed to be exposed (Figure 1), given potential contamination of the shared air and surface environment from droplet and fomite spread [5].
A total of eight HCWs in the general ward had cared for the patient while wearing surgical masks. However, none of the exposed patients or HCWs developed COVID-19 within the estimated incubation period [6], despite being closely followed up for 14 days.
Of note, the patient had complied with social distancing measures and had not interacted with any of the other exposed patients. At the patient’s initiative, he had worn a mask throughout the admission as an added precaution to minimize infection.
Minimizing nosocomial transmission of COVID-19 remains a challenge, given the wide spectrum of respiratory syndromes and mild respiratory symptoms at presentation [1].
Influencing patient behaviour to reduce the risk of patient-to-patient spread remains crucial. Social distancing between inpatients is important during an ongoing outbreak and should be reinforced in higher-risk areas.
References
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More information: S. Rawlinson et al, COVID-19 pandemic – let’s not forget surfaces, Journal of Hospital Infection (2020). DOI: 10.1016/j.jhin.2020.05.022
