By Thomas OH, Ph.D, Medical & Scientific Affairs for ASIA PACIFIC (Schülke & Mayr)
COVID-19 is a coronavirus belonging to the family of viruses which cause the common cold and ‘flu’ as well as more severe diseases, including Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). The current understanding of the transmission mechanism for COVID-19 is by close contact with infected secretions.
Although hand hygiene forms the basis of infection prevention, effective cleaning of surfaces particularly in the healthcare environment is essential. Viruses can survive on environmental surfaces for an extended period of time and transmission via an individual touching a contaminated surface has been shown to be possible, based on the understanding of other highly transmissible respiratory diseases, such as influenza. [1]
This means the risk of contracting coronavirus and becoming infected through touching contaminated surfaces is high. This is supported by a recent report on the persistence of various coronaviruses on different surfaces ranging from 2 hours to 9 days. [2]
This data together with another recent study on SARS-CoV-2 indicates that the virus responsible for causing COVID-19 could remain on uncleaned surfaces for many days. [3] Although the survival of the virus depends on a number of environmental factors, the underlying ‘risk’ of exposure presented to healthcare workers and patients should not be underestimated. Therefore besides good hand hygiene, adequate disinfection of the environment and equipment associated with patient care is imperative, to minimize the risk of infection.
An efficient disinfection process should always include a precleaning step to remove organic materials. The principle that only clean things can be efficiently disinfected is valuable. [4]
The first stage is to clean the surface and this initial wipe prepares a surface for the disinfection stage. Cleaning physically removes contamination, including some microorganisms and soiling if present. It is a vital step before disinfection, but does not necessarily destroy all microorganisms, even if a surface looks clean.
The second stage aims to reduce the number of microorganisms present to a level that is unlikely to cause infection. At this point, it is worth considering exactly what type of disinfectant/chemicals are present in the wipe being used. Wipes may look similar but may not always have similar antimicrobial properties.
According to Public Health England, ‘Effective infection prevention and control measures, including transmission-based precautions (airborne, droplet and contact precautions) with the recommended personal protective equipment (PPE) are essential to minimise risks. Appropriate cleaning and decontamination of the environment is essential in preventing the spread of this virus.’[5]
Before considering the most appropriate surface disinfectants for managing COVID-19, it is worth noting that coronaviruses are classified as ‘enveloped’ viruses, compared to other viruses, such as rotavirus, or poliovirus which are termed non-enveloped. Enveloped viruses possess an envelope or outer coating that is composed of a lipid layer (fat-like substance that is water insoluble). The envelope is needed to help the virus attach to the host cell. Loss of this envelope results in loss of infectivity.
Although Public Health England states that: ‘As coronaviruses have a lipid envelope, a wide range of disinfectants are effective’[5], a study in year 2012 examining Human Coronaviruses in relation to environmental resistance and disinfectant strategies strikes a note of caution, warning that despite the accepted fragility of enveloped viruses, they are potentially capable of developing significant environmental resistance. [4] For example, SARS-CoV has the ability to survive in different environmental conditions (low temperature and high humidity), on different materials found in hospital settings such as aluminium, sterile sponges, latex surgical gloves and in biological fluids. [4]
This makes human coronaviruses (HCoVs) ‘a challenging model for the development of efficient means of prevention’. [4] The study’s authors conclude that: ‘HCoVs are now known to show a significant environmental resistance’. Their survival in different biological fluids such as respiratory secretions or faeces has been proved.
To ensure the efficacy of a disinfectant against viruses, there is a recognised microbiological test against enveloped viruses, according to the European Norm (EN) standard named EN14476. A positive result means that the solution within the wipes/tissue is efficacious against enveloped viruses. Choosing a wipe with ‘virucidal efficacy against enveloped viruses’ combined with mention of EN14476 is a useful indicator for the selection of the disinfection wipe.
Passing the EN14476 test means that the disinfectant solution can kill viruses (eg. COVID-19 virus) but what influences the practical application of the wipe is the contact time which is the time required for the solution to be in contact with pathogens in order to eliminate or inactivate them.
This means that a disinfectant wipe could be EN14476 certified but may require a contact time of 5 minutes compared to another requiring only 30 seconds. A shorter contact time will save time and help simplify the cleaning/disinfection process.
Besides the disinfectant content, consideration should also be given to the material of which the wipe is composed, which is also key to achieving effective disinfection. The composition of the wipe needs to be capable of both containing and transferring the optimum amount of disinfectant onto the surface to achieve the antimicrobial effect. Of particular importance is the ability of the wipe to mop up and hold pathogens rather than just spreading them over the wiped area. The EN16615 test is the highest level of testing for antimicrobial wipes under the recognition of the European Standards committee. The test examines the efficacy of the wipe as a whole i.e. the wipe plus the disinfectant component.
When selecting a wipe for the clinical setting, it cannot be assumed that all wipes will have this ‘gold standard’ EN16615 certification. A wipe like mikrozid has both EN14476 and EN16615 certification. However, many wipes will have EN14476 certification without EN16615, which should raise the question, are these wipes really fit for purpose, when infection prevention has never been more important in this pandemic period?
As no specific therapies are yet available for COVID-19, early containment and prevention of further spread is crucial to stop the ongoing outbreak and to control this novel pathogen. Your choice of wipes has never been more important!
References
[1] Kraay ANM, Hayashi MAL et al, Fomite-mediated transmission as a sufficient pathway: a comparative analysis across three viral pathogens BMC Infect Dis.2018 Oct 29;18(1):540.
[2] Kampf G, Todt D et al, Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents J Hosp Infect.2020 Mar;104(3):246-251
[3] van Doremalen N et al, Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1, N Engl J Med, 2020 doi:10.1056/NEJMc2004973
[4] Geller, C., Varbanov M., Duval, R.E. Human Coronaviruses: Insights into Environmental Resistance and Its Influence on the Development of New Antiseptic Strategies; Viruses 2012, 4, 3044-3068
[5] Public Health England, Guidance Novel coronavirus (2019-nCoV) infection prevention and control guidance, updated 15th March 2020 https://www.gov.uk/government/collections/wuhan-novel-coronavirus
