COVID-19 pandemic: Cleaning and disinfection – What should the radiologist know?

Introduction

The current outbreak of the novel coronavirus SARS CoV-2, epi-centred in Hubei Province of the People’s Republic of China, has spread to many other countries. On 30^th January 2020, the WHO Emergency Committee declared a global health emergency based on the growing case notification rates at Chinese and international locations. As of 3^rd May 2020, the Ministry of Health and Family Welfare have confirmed a total of 26535 cases and 1223 deaths in the country since its first case on 30^th January.

Cleaning and disinfecting activities in hospitals are critical for preventing healthcare-associated infections. The purpose of this article is to consider the effects of COVID-19 on the imaging equipment, with particular consideration from the guidelines currently available from the Centers for Disease Control and Prevention, Ministry of Health and Family Welfare that may be applicable to radiology.[[1]] General principles to be followed while cleaning and disinfecting the radiology facilities and equipment are listed in [[Table 1]]. Various chemical disinfectants available in the market are highlighted in [Table 2] and [Figures 1], [2].

Figure 1: Chemicals used in cleaning and disinfection

Figure 2: Sterifog Fogging machine

Table 1

General principles to be followed for cleaning and disinfection

1. Wear proper personal protective equipment (PPE) - triple-layer surgical mask, disposable gown, heavy duty gloves, shoe cover, cap and face shield/ goggles while cleaning.

2. Always switch the system off at the main power before cleaning.

3. Follow manufacturer’s instructions for cleaning. Never mix household bleach with ammonia or any other cleanser.

4. X-ray and ultrasound systems should be covered with two-layer of fluid impermeable plastic if fogging is being done.

5. Alcohol solutions should contain ≤70% alcohol.

6. Do not shake dirty laundry.

7. Wash hands with soap and water after removal of gloves.

8. If soap and water are not available and hands are not visibly dirty, an alcohol-based hand sanitizer that contains at least 60% alcohol may be used.

9. While disinfecting facilities, care should be taken to ensure that the discharge of the vapours is sufficiently removed from the windows. Air must not be recirculated. Ensure ten air exchanges per hour.

10. Install exhaust ventilation systems in ultrasound and x-ray rooms.

11. The air-conditioning units should be switched off during the cleaning process.

12. Seal the equipment room with tape and plastic covering doors and vents during cleaning.

13. Downtime of at least 30-60 minutes is required after disinfection.

14. All instructions in the operator manual regarding cleaning and disinfection must be always observed.

15. Read all the instructions written on each disinfectant and cleansing bottle carefully before using.

Table 2

List of chemical agents for cleaning and disinfection[[2]–[4]]

Cleaning agents	Purpose and mechanism of action	Options
Aldehyde (high-level disinfectant)	Glutaraldehyde (1.0-1.5%) - excellent disinfective qualities against all bacteria, bacterial spores and viruses. The biocidal activity of glutaraldehyde results from its alkylation of sulfhydryl, hydroxyl, carboxyl, and amino groups of microorganisms, which alters RNA, DNA and protein synthesis.	Formaldehyde, paraformaldehyde, glutaraldehyde, calgocide 14, cidex and vespore
Quaternary compounds (Available as both high- and low-level disinfectant)	The bactericidal action of the quaternaries has been attributed to the inactivation of energy-producing enzymes, denaturation of essential cell proteins and disruption of the cell membrane. Their effectiveness and safety increase when they are combined with other disinfecting agents. They are not effective against hydrophilic viruses but are effective against lipophilic viruses.	Alkyl dimethyl benzyl ammonium chloride, alkyl dimethyl ethylbenzyl ammonium chloride, benzyl alkyl dimethyl ammonium chloride, didecyl dimethyl ammonium chloride, dioctyl dimethyl ammonium chloride, N-alkyl dimethyl benzyl ammonium chloride, octyldecyldimethylammonium chloride and quaternary ammonium chloride
Alcohol (Intermediate)	The most feasible explanation for the antimicrobial action of alcohol is denaturation of proteins.	70% ethyl alcohol Isopropyl
Chlorine derivatives (High-level disinfectant)	The germicidal action has been attributed to oxidation of sulfhydryl enzymes and amino acids; ring chlorination of amino acids; loss of intracellular contents; decreased uptake of nutrients; inhibition of protein synthesis; decreased oxygen uptake; oxidation of respiratory components; decreased adenosine triphosphate production; breaks in DNA; and depressed DNA synthesis	NaDCC (Sodium dichloroisocyanurate). Sodium hypochlorite (‘bleach’). Calcium hypochlorite Chlorine products are available as liquids or solid powders. The strength of a chlorine solution is expressed in ppm of free chlorine. Disadvantages of hypochlorite include corrosiveness to metals in high concentrations (>500 ppm), discolouring of fabrics.
Benzene (High-level disinfectant)	Interact with amino acids, proteins, and microorganisms. These chemicals kill spores by blocking the spore germination process.	Ortho-phthalaldehyde (OPA)
Alkylamines	Also referred as aliphatic amines. New category of germicidals effective against fatty acids.	Monoethanolamine and triethanolamine
Phenol derivatives (0.5-3%) (Low-level disinfectant)	In high concentrations, phenol acts as a gross protoplasmic poison, penetrating and disrupting the cell wall and precipitating the cell proteins. Low concentrations of phenol and higher molecular-weight phenol derivatives cause bacterial death by inactivation of essential enzyme systems and leakage of essential metabolites from the cell wall. Usually they are black or white fluids.	Ortho-phenylphenol, ortho-benzyl-para-chlorophenol, amphyl, staphene, hexachlorophene - Phisohex, chlorhexidine - Hibistat, Hiblicens and Lysol
Organic acids (High-level disinfectant)	Function similarly to other oxidizing agents-that is, it denatures proteins, disrupts the cell wall permeability and oxidizes sulfhydryl and sulphur bonds in proteins, enzymes and other metabolites.	Peracetic acid, carboxylic acid and acetic acid
Peroxide compounds (High-level disinfectant)	Peroxide compound works by producing destructive hydroxyl-free radicals that can attack membrane lipids, DNA, and other essential cell components. Hydrogen peroxide is active against a wide range of microorganisms, including bacteria, yeasts, fungi, viruses and spores	Hydrogen peroxide (3.0-6.0%)
Guanidine compounds	Bactericidal and fungicidal	Polyhexamethylene guanidine (PHMG)

Publication History

Received: 06 May 2020

Accepted: 17 July 2020

Article published online:
13 July 2021

• References

• 1 Centres for Disease Control. [Internet]. Available from: https://www.cdc.gov/infectioncontrol/pdf/guidelines/disinfection-guidelines-H.pdf. [Last cited on 2020 May 03].
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