Infection Prevention and Control/Surface Decontamination

Surface Disinfection for SARS-CoV-2

Ultraviolet Germicidal Irradiation

UV-C air disinfection was been explored extensively in the context of TB infection prevention and control by the South African scientific community in association with international experts. Protocols, guidelines and testing capacity for application of upper-room UVGI in airborne transmission have been established. This experience has provided important basic knowledge and key insights into the underpinning science and theory as well as application constraints, albeit for a different application.

Introduction

The coronavirus, SARSs-CoV-2, is understood to be transmitted primarily by contact and droplet spread.

Covid-19 is highly contagious and spreads more rapidly than its predecessors Severe Acute Respiratory Syndrome (SARS-Cov-1) and Middle East Respiratory Syndrome (MERS)</ref>, so any residual contamination can pose a public health threat. COVID-19 transmission remains controversial as researchers across the globe remain conflicted about droplet and airborne as modes of transmission. Clarifying the transmission routes and survival of viruses on frequently used surfaces is essential for containment of the outbreak. Research has successfully demonstrated that the virus has the potential to be aerosolised, and therefore can theoretically opportunistically transmit through the airborne route, it is understood that, except in aerosolising procedures, risk of coronavirus transmission via the airborne route is low. Similarly, risk via water and wastewater is low . Persistence of the virus on a variety of surfaces has been demonstrated , underpinning concern that SARS-CoV-2 may be transmitted from infected (even asymptomatic) persons to others from touching common surfaces, even after the infector has departed for several hours . Efforts to contain the coronavirus, to stem the pandemic, should therefore primarily focus on contact and droplet transmission. Contact and droplet transmission is of concern in public transport systems taxis which convey very large, transient populations in inevitably congested conditions such as in trains and mini-bus taxis. Transfer of Covid-19 suspected or confirmed patients in planned transport or emergency service vehicles pose a potential risk since studies show that conventional decontamination procedures may be incomplete . In a pandemic, and under already constrained infrastructure, overcrowding and proximity of infectious and susceptible individuals will become inevitable in healthcare settings, intensifying risk of Covid-19 transmission in these settings. The risk of temporary stock-outs of essential personal protective equipment for infection prevention and control during the outbreak is high. In the South African context, the reduction of exposure to Covid-19 is a priority, in order to:

• reduce and delay occupational exposure of frontline workers especially healthcare and transport services workers;
• reduce exposure to public health risk, especially to the most vulnerable, such as PLHIV and persons with TB who are the principal users of public transport;
• contribute to the strategy of “flattening the curve”; and
• preserve and protect the healthcare service so as to ensure continued service.

UV-C: potential for disinfection for SARS-CoV-2

The disinfection effect of ultraviolet light has been described for over 100 years. It is effective against a variety of microorganisms and has been successfully deployed for the purpose of disinfection of water, air and surfaces. Effectiveness depends on a range of variables related to the microorganism of interest, environment and application. Ultraviolet radiation in the UV-C range has been used for its germicidal properties specifically for infection prevention and control - have been demonstrated to work at laboratory scale, in ducts, as upper room irradiation and as portable devices. Safety guidelines have been established (ACGIH)<name="cite/>. There is good reason to expect that SARS-CoV-2 will be susceptible to UV-C. UV-C, when applied at the correct dose as it has been found effective against viruses [9] including human coronavirus [10, 11] (SARS-CoV-1). According to Kowalski et. al. [12], Covid-19 is susceptible to existing disinfection methods such as chemicals and exposure to ultraviolet radiation in the electromagnetic range ~ 200 – 280nm (UV-C) because of the similarity of its structure to other susceptible coronaviruses such as SARS-CoV-1 and MERS. UVGI surface disinfection has advantages over chemical disinfection because:

• There is no off-gassing of chemicals or residual chemical contamination frequently associated with chemical-based disinfection methods. Therefore, vehicles or spaces can be occupied immediately after UVGI disinfection [14, 15];
• It has high pathogen reduction rates when compared to chemical cleaning [14, 18]; and
• Chemical disinfection methods are time-consuming [16].

A guideline on hospital infection control [17, 18] recommends the use of both UVGI and chemical disinfection since UVGI has no penetrating power on dust, dirt and grease, which may harbour microbial contamination. Exposure to UV-C may degrade some materials. As SARS-CoV-2 is recent and novel, UVGI efficacy has not yet been established against this particular pathogen. Establishing definitive evidence will require identification and procurement of a suitable surrogate microorganism and determination of a Z-value. Testing facilities are available at the NIOH in Braamfontein, through the Immunology and Microbiology unit. NIOH protocols for testing are defined. The procedure for obtaining scientific evidence is underway and will be complete by the end of May 2020. For the reasons stated above, UVGI – the exposure of potentially contaminated contact surfaces to UV-C is identified as a measure with good prospects to reduce and delay occupational exposure of healthcare and transport services workers, as well as their clientele, and to contribute to the strategy of “flattening the curve”.