COVID-19 outbreak adversely influenced all fields of human activity worldwide. In her popular blog, Fiona Fox of the Science Media Centre listed 10 questions on various unknown matters about the virus and the disease. Virtually, the list included everything. A question she did not refer to was: How the virus contamination spreads in a hospital? A letter from researchers Dr. Stacey Rawlinson of University College London (UCL) and Great Ormond Street Hospital (GOSH) and others in the Journal of Hospital Inspection answered this crucial question.

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Researchers knew that due to droplet transmission, the UK has implemented a 2-m distancing. “While droplet transmission in air must be considered, and is a critical component to the safety of healthcare workers interacting with patients, it is also important to consider the role of surfaces," they asserted.

They noted that as per the current guidance, hospital staff should undertake surface cleaning a minimum of 20 minutes following an aerosol generating procedure (AGP) on a SARS-CoV-2-positive patient.

“However, there is little guidance on general surface cleaning in other contexts. SARS-CoV-2 remains viable for up to 72 hours on plastic and steel surfaces, and for up to 8 hours on copper and cardboard surfaces. Without effective surface cleaning, this can represent an important risk for surface-mediated transmission” they cautioned.

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The experimental study

In an elegant experimental study the researchers found virus DNA left on a hospital bed rail in nearly half of all sites sampled across a ward within 10 hours and persisted for at least five days. Overall, they took 44 samples each day: 20 from the immediate bed-space environment, 8 from the wider bed-space environment (e.g. cubicle door handles), 7 from clinical areas (e.g. height and weight room) and 9 from general ward areas (e.g. reception). They transferred the swabs into molecular grade water and processed them by quantitative polymerase chain reaction. They could readily remove the surrogate with hand-washing by adhering to the ‘Five Moments’ (explained later in the article) enunciated by the World Health Organization (WHO).

The researchers demonstrated that a single wipe (Clinell Universal or PDI alcohol wipe) could remove 98.88 to 99.84% of surrogate dried onto a surface. They did not take samples from the original inoculation site to prevent removal of the inoculation material

They did not use the SARS-CoV-2 virus; instead they artificially replicated a section of DNA from a plant-infecting virus, which cannot infect humans, and added it to a millilitre of water at a similar concentration to SARS-CoV-2 copies found in infected patients' respiratory samples. This is indeed a close enough surrogate for contaminated bodily fluid.

They placed 100 microlitres of water-containing 1150 million copies of the plant 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.

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Results

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.

Here is a press release from the University College London (UCL) quoted Dr Lena Ciric (UCL Civil, Environmental & Geomatic Engineering), a senior author of the study:

"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 contamination was very extensive. The highest proportion of sites that tested positive for the surrogate came from the immediate bed-space 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 bed-space area tested positive.

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Some queries

What are the reasons for choosing Cauliflower Mosaic Virus in this study?

Dr. Lena Ciric replied that the study used a short sequence of DNA so that there was no risk to humans. “This plant virus was chosen only because previous work had been performed using its sequence,” she clarified.

Can the results obtained in your study be considered general and broadly applicable to any site? 

“Yes, they can. If anything, we would expect the spread to be wider and quicker in a non-healthcare environment where there is less emphasis on hand hygiene and cleaning,” she responded.

The researchers have concluded that the scale of spread of the surrogate agent indicated cleaning failure. What are your suggestions to improve the situation?

“A novel training programme which puts more of an emphasis on why cleaning should be performed in a certain way, rather than just stating how it should be done,” she replied.

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Conclusions

According to the co-author Dr. Elaine Cloutman-Green (UCL Civil, Environmental & Geomatic Engineering), Lead Healthcare Scientist at GOSH, 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,” she cautioned.

“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 hand washing represent our first line of defence 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)," she clarified.

The press release from UCL noted that 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.

“While this study makes no comparisons between positive site and copy numbers required for infectious dose, the speedy and consistent spread of the surrogate DNA has important implications for infection control. As a high-risk area, the isolation room where the bed rail was inoculated had a different cleaning regimen to the rest of the ward; however, its wide dissemination indicates cleaning failure. As the surrogate is removed readily with good hand hygiene, this also indicated hand hygiene failure,” the researchers observed.

Healthcare workers cannot prevent the spread of the virus during aerosol generating procedures (AGPs) and contact with infected patients unless they undertake procedures for strict hand hygiene, careful donning and doffing of personal protective equipment, and consistent cleaning.

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Five Moments for Hand Hygiene

Health care workers must follow ‘Five Moments for Hand Hygiene’ stated by the WHO. Moment 5 (hand cleaning after touching patient surroundings) is particularly relevant.

“It is important to consider all methods of transmission, including the risk from surfaces. To reduce the risk, the first line of defence for preventing the spread of SARS-CoV-2, and other potential pathogens, is effective cleaning. SARS-CoV-2 is an enveloped virus; as such, it is very susceptible to most cleaning agents, which destroys the envelope and deactivates the virus," the researchers concluded.

This study highlights the role of surfaces as a reservoir of pathogens and the need to address requirements for surface cleaning.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

Dr K S Parthasarathy is a freelance science journalist and a former Secretary of the Atomic Energy Regulatory Board. He is available at ksparth@yahoo.co.uk