Cleaning Guidelines and Studies from Various Countries: COVID-19 and Cleaning

Coronaviruses have existed for years, but the novel coronavirus is highly contagious and causes serious health problems in a certain percentage of infected individuals, straining medical services.

Hundreds of studies have been conducted over the past year; for instance, our Finnish colleagues had completed 560 studies by December 2020. However, we can still conclude that definitive data on the role of cleaning in the spread of the novel coronavirus is lacking. The following is an overview of what these studies highlight.

What type of virus is COVID-19?

SARS-CoV-2 is a 50–200 nanometer virus with a lipid or fat capsule (envelope). Enveloped viruses don‘t tolerate the effects of biocides, heat, and UV light well, meaning they are generally susceptible to disinfectants. Studies have shown that SARS-CoV-2 is sensitive to ultraviolet radiation, 70% ethanol, chlorine compounds, peracetic acid, and lipid solvents. As the temperature rises, the viability of the coronavirus decreases. Research indicates that the coronavirus is destroyed after 30 minutes in a 56°C environment. The virus also perishes on antimicrobial surfaces. We can assume that furnishing elements with such surfaces will become more common in the future.

The virus primarily spreads as airborne droplets, which are generated during breathing, speaking, singing, and similar activities. Typically, these droplets settle on surfaces up to 2 meters away. If the droplet size is less than 5 micrometers, they are referred to as aerosols, which remain airborne for a long time and spread through the air, a fact supported by studies.

Viral Load on Surfaces

In many studies, the virus has been found on various surfaces. The highest concentrations are found in rooms where COVID-19 patients are cared for. For example, in hospital intensive care units, the virus can be present on up to 50% of surfaces (source). There are studies where the presence of the virus has been examined on commonly used surfaces. In some studies, small amounts of the virus have been found, such as in public transport and hotels. The virus remains viable on surfaces but does not multiply, as it requires a living cell for reproduction. However, it can be said that the infectious virus has been found on surfaces extremely rarely. Rather, what is found is the virus’s genetic material, which is no longer infectious.

The virus can also attach itself to protective equipment – gloves, clothing, masks, etc. Consequently, the correct handling of used protective equipment is crucial to prevent the virus from transferring from the equipment to hands and other surfaces.

The presence of the virus after cleaning has also been studied. The results generally show that conventional cleaning removes microbial contamination from surfaces. What exactly “conventional cleaning” entails has not been specified in the studies. We emphasise that conscious cleaning is of decisive importance both in combating COVID-19 and in general.

The effect of different surface materials on virus persistence has also been studied. It has been found that on smooth surfaces such as glass, steel, and plastic, the virus persists longer than on wood and textile surfaces. Research showed that the virus persisted on steel and plastic surfaces for up to 72 hours, on cardboard for 8 hours, and on copper for 4 hours, but the viral load significantly decreased. In addition to the surface material, temperature and humidity are also important influencing factors. It has been concluded that the virus remains infectious for the longest at +4°C with 40% humidity. However, the virus also persists at room temperature. The persistence of the virus is also affected by whether the virus is part of something that enhances its viability (e.g. sputum, mucus). If the substance surrounding the virus dries, its viability also decreases. Similarly, the viral load is a decisive factor in its viability. Thus, there are several influencing factors. According to research data, the virus can remain infectious for a few hours to a few days.

Microorganisms can spread on surfaces as follows:

1. A contact surface is contaminated, e.g. the edge of a door
2. From there, it can transfer to the hands of 14 people
3. Each of those people can transfer it to up to 7 surfaces, meaning 14 x 7 = 98 surfaces become contaminated
4. Each person can infect 6 people, meaning a total of 14 x 6 = 84 people

This is why the cleaning of contact surfaces must be given special attention.

Cleaning or Disinfection?

Microorganisms can be neutralised by either removing them from the surface or destroying them. Removal generally means wiping with a microfiber cloth, and destruction means disinfection. Studies show that wiping with a microfiber cloth can remove 99–99.9% of microorganisms from surfaces. However, it is important to consider what level of result is sufficient. For example, intensive care units and public transport require different standards.

Several studies have highlighted the problem of transferring dirt while wiping surfaces. This occurs if the cleaning cloth is not folded properly to present its clean sides. The principle should be “one wipe, one surface, one direction.” Several studies indicate that wiping technique is a decisive factor.

Disinfection destroys microorganisms remaining on the surface. This can be done as either a 1- or 2-step process.

• In the 1-step method, only a disinfectant cleaner is used. The problem with this method is that dirt is known to reduce the effectiveness of disinfectant.
• In 2-step disinfection, surfaces are first wiped and then disinfected. This removes dirt that would reduce the biocide’s effect before performing the disinfection. This method is highlighted in the COVID-19 guidelines of several countries. However, it is time-consuming and resource-intensive.

For both the 1- and 2-step methods, the biocide’s contact time must still be observed. This can be up to 15 minutes for some disinfectant cleaners. Studies and coronavirus guidelines from various countries emphasise a 1-minute contact time for the disinfectant in the 2-step method. Therefore, it is always necessary to consult the usage instructions for the product being used.

Transmission via Surfaces

Various studies indicate that the probability of infection via surfaces is low but possible. Surface transmission is a realistic consideration when there are many COVID-19 patients in a room, resulting in a high viral load on surfaces. There are studies suggesting that the presence of mucus and/or sputum is also necessary for the virus to persist on a surface. The aforementioned study recommended using disinfectants only in cases involving secretions. Conscious maintenance cleaning is important. Additionally, it should be mentioned that hand hygiene and avoiding touching the mouth, nose, and eyes are still of significant importance.

Selection of Cleaning Method

To date, most studies have been conducted in hospital environments. Consequently, in addition to the importance of conscious cleaning, the use of disinfectants has been highlighted. However, it must be emphasised that unnecessary and incorrect use of disinfectants should be avoided. Excessive and incorrect use of disinfectants makes microorganisms more resilient, and certain microorganisms may become resistant.

One can also refer to a 2019 study conducted in Canada, which states that a microfiber cloth moistened only with water cleaned the surface by 98.4%. However, no substance could completely clean the surface of drug residues. The study used microfiber cloths from five different manufacturers.

It would be important to conduct additional research on cleaning activities in the context of the novel coronavirus. One such example is a study by Tampere University, the results of which will be published in spring 2021, and Puhastusekspert actively stays up-to-date regarding the newest research.

This article was written in cooperation with Tarja Valkosalo, Artikkelit Archives – PROPUHTAUS.

Puhastusekspert’s Concluding Remarks and Recommendations for Cleaning During Viral Outbreaks:

• Aware and correct use of protective equipment;
• Virus persistence varies on different surfaces, also influenced by the temperature and humidity of the given environment;
• There is a higher probability of encountering the virus on smooth surfaces such as steel, plastic, etc. if they are contaminated. However, these surfaces are also easier to clean;
• Awareness and conscious cleaning of contact surfaces are key factors;
• Dirt promotes virus persistence, especially in the case of secretions. Therefore, the immediate removal of secretions and cleaning of contact surfaces are paramount;
• Cleanliness of cleaning tools, which prevents the transfer of dirt;
• The most important aspect is conscious cleaning activity – asepsis, skilful use of cloths, appropriate moistening, mechanics, selection of dirt-removing and binding methods, etc.

Conscious cleaning is key!