Sampling of Contaminated Surfaces for SARS-CoV-2 (Coronavirus)

Posted by mpolkabla On April - 15 - 2020

As our businesses, communities, and families come out of this worldwide pandemic, we will also need to determine when it is “Safe” and appropriate to do this. The intent of the current Shelter In Place (SIP) orders were specifically designed to limit the spread and transmission of the SARS-CoV-2 (Coronavirus) from exposures associated with person-to-person transmission as well as from surface contact and transmission where the SARS-CoV-2 virus may be present. The ongoing professional and technical debate relative to surface contact transmissions is an active and lively one… Studies (primarily with the previous SARS-CoV-1 virus) have shown that actively viable virus (meaning able to replicate) can remain present on varying surfaces for as long as 3 days and possibly longer. Based on these previous studies and our current understanding relative to the active transmission of the SARS-CoV-2 (Coronavirus) that has resulted in the United States Centers for Disease Control (CDC) as well as the World Health Organization (WHO) to recommend that disinfection of surfaces be performed where the potential for SARS-CoV-2 virus is known and/or where it might exist. Such disinfection is critically important within places such as medical facilities and quarantine areas where confirmed COVID-19 patients were present, but is also important within public areas, places of business, and residences where residues and deposits containing viable virus might also remain in the form of foamites, droplets, and/or physical residues. Therefore, it is very important to disinfect these potentially contaminated areas and surfaces (as discussed in my previous article) and where necessary, to provide meaningful verification once these areas and surfaces are disinfected and determined “clean” so that these areas and surfaces may be used safely again.

To achieve this follow-up verification, there are two methods currently available to industrial hygienists to use so as to evaluate the success (or failure) of such disinfection methods. These post disinfection sampling methods are known as the Adenosine Triphosphate (ATP) and the Reverse Transcription – Polymerase Chain Reaction (RT-PCR) amplification and sampling methods. In general, both methods employ the use of surface sampling and analysis techniques to collect and measure remaining residues (following disinfection) looking for what we call “surrogate” indicator markers of the SARS-CoV-2 virus itself. The ATP analysis method is currently used in a wide range of industries such as agriculture, food and beverage processing, and even medical facilities where surfaces are regularly cleaned and disinfected. Since ATP is an indicator of active “biological activity” the presence of ATP on a surface is also an indicator of such activity on that surface. Hence, if a surface is appropriately “disinfected” (using a prescribed method such as recommended by the CDC), then ATP should not be present or detected within the representative sample of the cleaned surface. A number of companies use ATP detection systems to rapidly verify surfaces have been cleaned thoroughly and to ensure that biofilms are not developing on the surface that could contain viable microbial contamination. Thereby, the verified absence of detectable ATP on a sampled surface is considered a surrogate indicator that the surface has been appropriately cleaned based on the absence of biological activity. An additional value in the ATP sampling technique mentioned is that this method can be performed by a trained industrial hygiene technician on site with sampling results available in about 20 minutes per sample. Equipment utilized with the ATP methods consists of pen-type swab media that is wiped across a surface and then placed into a hand-held luminometer reader that measures the presence or absence (as well as levels) of ATP present within the sample.

By contrast, the RT-PCR sampling an analysis method detects the actual genetic signature RNA of the SARS-CoV-2 virus in swab samples from contaminated environmental surfaces using clinical instrumentation detection techniques. These sampling and analytical methods are designed to measure the presence (or absence) of the specific indicator genetic RNA marker materials of the SARS-CoV-2 virus itself once received and analyzed at the analytical laboratory. The great benefit in this type of method is that it is a specific to the SARS-CoV-2 genetic viral material but is limited in that it takes a minimum of two days from sample collection to receipt of results. In addition, this method measures the viral Ribonucleic acid (RNA) and is of itself not an accurate indicator of current viral activity but rather that evidence of the virus was there (based on the RNA that remained). A good analogy of this would be that of a crime scene where specific finger prints (or blood stains) were identified present, but where the criminals and victims were long gone from the scene and only evidence is all that remains. Hence, all we can determine from the presence of the RNA specific marker was that the SARS-CoV-2 virus was once there, but not necessarily viable (or active) at the time of collection. Sampling methods employ the use of viral swabs that are collected from representative surfaces and processed by the trained industrial hygiene sampling technician using Chain of Custody (COC) documentation for transport via priority mail to the analytical laboratory.

Although neither of these methods are intended measure the viable SARS-CoV-2 virus itself, these two methods are extremely valuable in verifying whether the disinfection methods as employed were successful. This determination is effectively made by looking for the presence of ATP biological activity or the presence of viral SARS-CoV-2 RNA indicator markers using these two methods.

So the big (and fair) question is whether it is important to sample potentially contaminated surfaces at all… The choices to consider are simple:

1) Assume that surfaces are absent of viral contamination… Meaning do nothing and hope for the best.

2) Perform some form of disinfection and assume this was effective based on what actions were performed. or

3) Disinfect surfaces (following CDC recommendations) and where it is critical or desired to do so, perform meaningful verification sampling based on the current technologies and methods described here.


If verification sampling of surfaces is deemed necessary or desired for whatever reason, please feel free to contact us to review your specific situation and needs where we can develop a plan to assist and answer these important questions.

Be well and stay Safe…

Michael A. Polkabla, CIH, REA

Senior Certified Industrial Hygienist, Principal

BioMax Environmental, Inc.