Cleaning, Disinfection, Sterilization: What is the Difference?

In the Corona pandemic, the desire for hygiene and sterility is high. Most people should know by now that washing hands with soap and warm water for about 20 to 30 seconds is one of the simplest and most effective methods of fighting the potentially deadly virus.

But there are other ways to protect yourself. What the differences between cleaning, disinfectionn or sterilization are, however, still not clear to many people. The three terms are often used synonymously. What all three methods have in common is that their ultimate goal is to remove dirt, pathogens and germs.

The term cleaning describes the mechanical removal of visible impurities such as dust or dirt, but also of invisible organic material. The aim of cleaning is to prevent microorganisms from multiplying on the surfaces. Normally a solution of water, soap or enzymatic cleaners is used for cleaning. Scrubbing is done with hands or brushes, but more sophisticated methods such as ultrasound are also used to clean surfaces, e.g. in kitchens or bathrooms.

Although cleaning reduces the microbial population, it does not kill germs, bacteria and infectious microbes. Even when no more impurities are visible, surfaces can still be contaminated with viruses. According to the German Robert Koch Institute (RKI), cleaning can reduce the concentration of pathogens on a surface by 50 to 80 percent. For effective infection control, however, cleaning can only be a first step.

The aim of disinfection is to reduce the number of pathogenic germs to a safe level so that the object no longer causes infection or pathogen transmission. This means the killing or inactivation of pathogens to prevent infections. The possible reduction of germs during disinfection is more than 99.999 %. After an optimal disinfection, only ten germs remain from one million germs, with 10,000 germs this number is even reduced to 0.

With the outbreak of COVID-19, the demand for hand disinfectants has also increased significantly. If a disinfectant consists of at least 70 percent isopropyl alcohol (IPA), the risk of contracting coronavirus can be minimised.

Since many disinfectants do not necessarily remove the dirt from a surface, cleaning is an important first step before disinfection. Disinfectants can only develop their full effect if they are used according to the manufacturer's instructions and in the correct dosage. For example, if a surface disinfectant takes two minutes to eliminate enveloped viruses (such as corona viruses), it does not have a disinfecting effect if the treated surface is wiped clean after only one minute.

Sterilization is much more aggressive than disinfection. The aim of sterilization is absolute sterility. Sterilisation means the killing of all micro-organisms including the bacteria spores. After an optimal sterilisation, none of one million germs remain. An object is classified as sterile if the probability of a living germ being present on the object is less than 1:1,000,000 (one million).

In other words, for every one million sterilized objects, there may be no more than one living microorganism left on any one object. This is particularly necessary in medical facilities: instruments such as syringes, scalpels or surgical scissors must be sterile when they penetrate into internal body regions or come into contact with wounds.

Against the novel coronavirus SARS-CoV2 "limited virucidal" disinfectant helps. Other germs require different disinfectants due to their external structure, for example the norovirus. Agents with an "antibacterial" effect, on the other hand, only remove bacteria and are not suitable for effective disinfection in the current corona pandemic.