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Effective strategies for killing coronavirus on surfaces

Many people are practicing social distancing, and carry out other measures to reduce the spread of the novel coronavirus SARS-CoV-2, like regular hand-washing. It is also important to ensure that surfaces, especially in public spaces, are regularly cleaned and disinfected.


Surface survival

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There have been two studies published on the novel coronavirus and its ability to survive on surfaces. The first is from the Journal of Hospital Infection (“Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents”) the second is published in the journal Infection Prevention in Practice (“Potential role of inanimate surfaces for the spread of coronaviruses and their inactivation with disinfectant agents”).

The main risk is with the length of time, which from the two papers is:

The survival of the virus on metal is up to 24 hours;
The survival on plastic is up to 9 days.

Other types of surfaces are also detailed. This means that any surface could potentially be contaminated, and hence regular cleaning and disinfection is required in public spaces.

READ MORE: Coronavirus update: Round up of positive news stories

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Cleaning or disinfection?

In relation to killing the virus on surfaces, there is a difference between cleaning and disinfection (to often disinfection becomes conflated into cleaning). Cleaning, which involves the use of anything from water to detergents, is effective at removing material from surfaces and for disassociating microorganisms from surfaces. Disinfectants, on the other hand, kill bacteria and viruses directly. While it is possible to apply a disinfectant to clean surfaces, where there is dirt on a surface, the surface should be cleaned first before the disinfectant is applied.

Disinfection or sanitization?

The terms ‘sanitizer’ and ‘disinfectant’ are often confused. They generally refer to the same biocide, with the same intended level of microcidal activity, against pre-set criteria. Both are chemicals when marketed into the healthcare market are designed to be applied to inanimate objects for the purposes of reducing the number of microorganisms present to an acceptable population. In other words, the terms are interchangeable.

A pharmacy technician learns the correct procedure for disinfecting a vial of medicine.
A pharmacy technician learns the correct procedure for disinfecting a vial of medicine.
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ALSO READ: First treatment option for COVID-19 developed

What to disinfect with?

The virus is very easy to kill using disinfectants to clean surfaces. The consensus from the two recent research papers is:

The minimum alcohol content is 61%, with a kill achieved in 30 seconds. Here the best alcohols are ethanol or iso-propyl alcohol (IPA)
Benzylchlorine based wipes, such as the types sold by supermarkets for kitchens, also work well, and can kill the virus within one-minute.
Hydrogen peroxide in liquid form at 0.5% or greater is very good, again less than one minute contact time.

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By contact time, this is the time that the disinfectant needs to be in contact with the surface. The surface needs to remain wet for this period of time (that is the user should not attempt to dry the surface before the contact time has elapsed and if the surface appears to dry before the contact time has been reached, reapply the disinfectant).

What appears less effective is ‘fumigation’, for example, however, hydrogen peroxide vapor will work but it takes a long time, with a contact time if 1 to 2 hours.

Importantly, the disinfectants mentioned are not suitable for use on bare skin, including alcohols which can dry out the skin and there is a risk of developing dermatitis. The only exception is ethanol that has been denatured (what is sometimes called ‘industrial methylated spirit’). The best skin sanitizer is something like chlorhexidine, which is commonly used in hospitals as a general sanitizer and to disinfect skin prior to surgery.

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