Current hygiene guidelines appropriate for UK and SA variants of SARS-CoV-2, study finds

Many different variants and lineages have arisen from the ancestral Wuhan-Hu1 strain of the severe acute respiratory syndrome coronavirus (SARS-CoV-2). This requires careful attention to control measures since many are more infective and transmissible than the older strains. A recent study, released as a preprint on the bioRxiv* preprint server, compares the UK variant of this virus with the wildtype in terms of susceptibility to routine cleaning and disinfection measures.

The SARS-CoV-2-caused pandemic of coronavirus disease 2019 (COVID-19) is largely spread by respiratory droplets and aerosols containing the virus, from infected people. However, scientists have warned that the infectious particles in the air can settle on nearby surfaces and on fomites, to produce transmission, though this is not a major route of infection.

Variants of concern

The recent emergence of the UK variant, B.1.1.1.7, with a group of mutations at the spike and other regions, has been followed by its rapid rise to dominance in the UK and its rapid spread to other countries. This has led to its being reported as a variant of concern (VOC), with higher transmissibility and reproduction numbers than the older variants.

In some cases, VOCs have also been associated with increased severity of the infection and immune evasion, allowing reinfection of immune individuals. This is the case with the South African variant, B.1.351.

The rollout of several safe and effective vaccines was supposed to be the beginning of the pandemic's end. However, the logistical challenges as well as the demonstration of resistance to vaccine-elicited antibodies by the VOCs have made it essential to continue non-pharmaceutical interventions for the time being.

These include face masks, hand sanitization and physical distancing. Environmental contamination is also an area of possible concern, especially in healthcare facilities where there are often a large number of infected patients with a high rate of viral shedding, in a relatively small space.

This has meant that environmental contamination requires to be dealt with in order to limit the spread of the virus by inactivating it. The current study compares the wildtype or B1.1.70 variant with the B.1.1.7 and B.1.351 variants in terms of its sensitivity to three inactivating agents: heat, soap and alcohol.

Comparable inactivation between variants

The researchers found that the three variants were equally inactivated on exposure to alcohol at 30% w/v for 30 seconds or more.

Secondly, when using commercially available hand soap, in a 1:49 dilution, all three variants were inactivated after a period of exposure ranging from 1-5 minutes.

Alcohol is harsh on the skin, and hence not recommended for routine use. Soap contains surfactants that act on the lipid envelope of the virus to disintegrate it in a matter of minutes.

Common handwashing routines are completed within less than two minutes, so this cannot be the only mechanism. It is supplemented by the elution of the viral particles from the hands' surface, as the hands are rubbed against the soap particles, which adsorb the virus, and the mixture washed off.

This finding indicates the validity of the currently recommended handwashing guidelines in preventing viral transmission. Of course, the ratio of soap and water can affect the contact time necessary for inactivation. The small differences found between the variants do not need to reflect their biology.

When heated to 56°C or more, all three strains were found to be susceptible, showing reduced viral titers, and reaching background levels within 30 minutes of heating.

Stability on environmental surfaces

The virus stability on various surfaces was also examined, using a representative sample in the form of silver, copper and stainless steel. The infected material was allowed to remain in contact for up to 48 hours.

This showed that the wildtype virus, as well as the three VOCs, had comparable infectivities. This was repeated when the inside of a surgical or FFP2 mask was contaminated experimentally. This emphasizes the need to change masks regularly and to use separate masks.

Silver did not show any antiviral properties, in contrast to other studies, though copper surfaces did inactivate the virus effectively.

What are the implications?

The findings show that the currently circulating VOCs are not more stable than the earlier strains, and are equally susceptible to inactivation by ordinary methods of disinfection. This implies that the current measures of environmental hygiene are both adequate and appropriate for environmental disinfection in situations of possible contamination.

*Important Notice

bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.