Study reveals stability and density of SARS-CoV-2 contaminants on common surfaces

A recent environmental study from the United Kingdom, currently available on the bioRxiv * preprint server, indicating that some common surface may represent an infectious risk if contaminated with a high density of severe respiratory coronavirus syndrome 2 (SARS-CoV-2) – although the level of susceptible viral grains tend to be low.

The global pandemic of coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has been successful as a result of viral spread through a number of different pathways, including human contact with surface corrupt. Humans are usually contaminated either by droplets containing a virus or by rubbing.

As a result, many researchers have used molecular analysis methods to detect SARS-CoV-2 genetic materials on different surfaces; however, a working virus has rarely been detected. This means that the risk of infection from the surface of viral contamination is somewhat challenging to predict, including further studies to enhance our understanding of survival.

This new paper by UK researchers (led by Dr Susan Elizabeth Paton from the English Public Health Service, National Disease Service in Wiltshire) aimed to assess the functional viability of SARS-CoV-2 across specific time after drying on a range of materials, but also to compare the viability of the virus with recovered RNA copies and dependence on the possible density dependence.

Circulating common materials

In this study, the researchers decided to use a surface that represented non-porous hand-rubbed sites (such as stainless steel) and banknotes (i.e., 10 GBP English polymer notes) and personal protective equipment materials that are dangerous in a health care setting and the wider environment, such as layered surgical masks, disposable plastic gowns, and coveralls. This was complemented by materials that represented clothing items, such as polyester sports shirts and cotton T-shirts. Coupons the size of 1×1 cm of each material were prepared.

The SARS-CoV-2 snort was first isolated using Vero E6 cells (derived from the kidney of an African green monkey), and viral aliquots were disinfected to room temperature just before products to include. The virus was recovered from the coupons, and a plaque assay was then performed. RNA analysis and re-chain-polymerase chain reaction (RT-PCR) were also followed.

When concerned with data analysis, each timepoint had three biological reactions (i.e., individual coupons) and two technical reproductions (i.e., a double-assay plaque assay). all material coupon used.

Optimum stability of non-porous hydrophobic surface

This study showed that the UK isolated SARS-CoV-2 could remain viable on a hydrophobic surface for up to seven days. The workability of a hydrophilic surface is basically reduced to three days at a temperature of relative humidity environment.

In particular, the viable virus was the longest-lasting stainless steel and surgical mask (more than 100 times for a 99.9% reduction in SARS-CoV-2 functional capacity for both materials), while in which the fastest fall was observed on a polyester shirt (99.9% reduction in 2.5 hours), followed by cotton (99.9% reduction in 72 hours).

In any case, SARS-CoV-2 was most stable on a non-porous hydrophobic surface, and viral RNA was highly stable when dried on the surface – with only one log reduction in yield over three weeks. However, it was shown that the functional capacity of SARS-CoV-2 decreased much faster, and that rate of decay was independent of the onset of congestion.

Possible genetic material vs virus

The study concludes that expected levels of potential SARS-CoV-2 environmental surface contamination lead to unstable levels within two days. In other words, when a viral genetic material (RNA) is found on the surface, it does not directly suggest the presence of a viable virus.

“This influences the interpretation of surface sampling results using RT-PCR to determine whether it is possible to detect susceptible viruses from a surface,” study authors cautioned here bioRxiv paper. “If they are not sampled immediately after contamination, it is difficult to align RNA copy numbers with the level of surface-susceptible virus”, they add.

Future studies may address this conventional limitation, where the copy number is found for much lower concentrations of SARS-CoV-2 present on the surface. As a result, this will help to identify whether RNA stability is independent of viral density and clarify the true relationship to be found over an operating virus.

* Important message

bioRxiv publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be seen as final, guiding health-related clinical practice / behavior, or be treated as information established.