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Surface sampling of coronavirus disease (COVID-19)

Surface sampling of coronavirus disease (COVID-19)

What is COVID-19?

The disease COVID-19 (“corona virus disease 2019”) is caused by an RNA virus, SARS-CoV-2. So far it is known that this virus emerged in Wuhan in China in December 2019. Fever, cough and difficulty breathing, are the most frequent symptoms, which can lead to the onset of pneumonia. By now, it's common knowledge that the coronavirus can be spread by being in close contact with someone who's infected and then breathing in their respiratory droplets. Or by touching a contaminated surface and rubbing your eyes, nose or mouth.

Why should we monitor COVID-19 on the surface?

People with the virus may leave infected droplets on objects and surfaces (called fomites) when they sneeze, cough on, or touch surfaces, such as tables, doorknobs and handrails. Other people may become infected by touching these objects or surfaces, then touching their eyes, noses or mouths before cleaning their hands.

According to the National Institutes of Health (NIH), the coronavirus can survive for two to three days on plastic and stainless steel surfaces.

This is why it is essential to thoroughly clean hands regularly with soap and water or an alcohol-based hand rub product, and to clean surfaces regularly.

The solution to protecting workers against COVID-19 requires a multi-faceted approach. In addition to the well-established need for masks, companies also need to control, monitor and ensure SARS-CoV-2 free environmental conditions.

In this way, the detection of the virus in surfaces becomes relevant as a screening technique, allowing hospitals, healthcare, industries, hotels, settings to decontaminate positive areas.

How can we do it?

1 - Surface sampling
The first step is to identify and list the common areas or surfaces, such as doorknobs, handrails and working surfaces to be tested. Wet the swab with viral transport medium, and apply pressure with the wet swab onto the surface, move in at least two different directions while rotating the swab stick. The recommended swab surface area is 25cm2 per swab.

2 - Processing of samples in the laboratory
In the laboratory, swabs go through a process that involves the extraction of RNA. In this step, it is intended that the RNA of the viral particles (if present) is isolated from the samples for the next step the detection.

3 – Real Time RT-PCR
The detection of the virus is done through a diagnostic test, called Real Time PCR. This technique is relatively quick, sensitive and very specific. It combines amplification targeting small fragments of the virus genome for detection with specific probes.

Potential risks of analysis

Negative results do not rule out the possibility of infected surfaces. There are several factors for the existence of false negatives in the analyzes carried out on surfaces, such as:

1. Sample collection: the choice of the test zone does not represent the entire surface and the zone tested could contain few or no viral particles in the sample; This problem can be mitigated if several samples are collected to cover most of the surface;

2. The specimen collected was not handled and / or properly sent to the laboratory. This problem can be mitigated if the sample during collection and transport is refrigerated;

3. Technical reasons inherent to the test, including mutations in the viral genome or inhibition of PCR amplification reactions. This last point is taken care of by using the ViroReal® Kit SARS-CoV-2 & SARS, which detects a highly conserved region of the N gene present in all SARS coronaviruses. This approach allows for universal detection of all known strains of SARS-CoV, including SARS-CoV-2 and SARS without discrimination between strains. The discrimination can then be confirmed by using the ViroReal® Kit SARS-CoV-2;

References:
WHO (2020): Surface sampling of coronavirus disease (COVID-19): A practical “how to” protocol for health care and public health professionals. Version 1.1, 18th February 2020.