The subject of this week’s coronavirus opinion piece is about surface survival and disinfection. That is with how long the virus can remain on different surfaces for as well as some of the optimal disinfectants that can inactivate the virus.
READ MORE: COVID19 — Put away that face mask, save it for healthcare workers
Earlier research into other coronaviruses (SUCH AS “Survival of human coronaviruses 229E and OC43 in suspension and after drying on surfaces: a possible source of hospital-acquired infections“) demonstrates how these types of viruses can remain infectious for between 2 hours and 9 days on different types of materials, based on standard ‘room temperature’ (approximately 20 degrees celsius) conditions.
This is important given the 79 percent genetic similarity between the current coronavirus of concern – named SARS-CoV-2 and the original SARS virus that made headlines in 2003.
Studies show survival times differ according to surface type. Worst cases show:
Steel at 3 to 28 days
Aluminium up to 8 hours
Paper up to 5 days
Glass up to 5 days
Plastic up to 9 days
Latex – as used to make many gloves – 8 hours
It should be noted that across the different studies cited, the viral load varied (from 1000 to 100 million). It is also important to note, each of the methods looked for presence of coronavirus RNA. The detection of RNA does not necessarily mean the viral material remains infectious.
However, for safety the findings suggest that any of the surfaces could potentially be contaminated, through viral material remaining on the surface for a substantial period of time. Hence, regular, cleaning and disinfection is an important contamination control measure.
Temperature appears to be an important factor with surface recovery. A higher temperature, such as 30 to 40 degrees Celsius, is associated with a shorter persistence of coronaviruses (coronaviruses appear to be inactivated at temperatures of 60 degrees Celsius and higher). There is a greater concern at lower temperatures, where studies reveal that at 4 degrees Celsius the ability of coronaviruses to survive on surfaces, like stainless steel, increases to more than 28 days.
With cleaning and disinfection, cleaning, is effective at removing material from surfaces o that disinfectants will work better – such as applying a detergent. In many cases, cleaning is a key pre-step. Disinfection is about using the appropriate agents to inactivate coronaviruses.
So, what are the best disinfectants?
There are two papers into SARS-CoV-2 which match earlier research into coronavirus, both from Kampf and both published in the past couple of weeks. The first is “Persistence of coronaviruses on inanimate surfaces and its inactivation with biocidal agents” and the second is titled “Potential role of inanimate surfaces for the spread of coronaviruses and their inactivation with disinfectant agents, Infection Prevention in Practice” (these papers have similar titles).
Both papers show, connecting with earlier research:
Alcohol is effective at inactivating the coronavirus, with inactivation achieved in 30 seconds. The optimal alcohols are ethanol or iso-propyl alcohol (IPA), with a concentration of between 61 percent and 71 percent. These alcohols are appropriate for surfaces as well as gloves and skin. With skin, the hand sanitizer should contain moisturisers to prevent dermatitis.
In addition to alcohol-based disinfectants, hydrogen peroxide in liquid form at a concentration of 0.5% or greater has also shown to be effective against SARS-CoV-2, again less than one-minute contact time. For home use, household bleach at 0.5% is also effective, with a one minute contact time.
By contact time, this refers to the time that the disinfectant needs to be in contact with the surface. The surface needs to remain wet for this period of time.
The following video expands on some of the material in this article:
Importantly outside of your home, it is useful to consider that any surface could be contaminated – so either disinfect the surface or wash your hands with hot soap and water after touching the surface of concern.
