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By Hassan Vally

One of the many challenges over the course of the past two years has been in understanding the importance of the different routes of transmission of the SARS-CoV-2 virus that causes Covid-19. Understanding the role of the different infection pathways plays a vital role in prioritising what we should be doing to prevent disease.

The World Health Organization advises Covid-19 transmission mainly occurs during close personal contact and via aerosols in poorly ventilated or crowded spaces. But the WHO also acknowledges people can become infected by touching their eyes, nose or mouth after coming into contact with contaminated objects or surfaces.

Over time we have seen a reduced emphasis on preventing surface transmission and a greater focus on preventing person-to-person and aerosol transmission. This focus reflects how our understanding of transmission pathways has improved but it is still important to understand as much as we can about surface transmission.

New Japanese research – published online and not yet reviewed by expert peers – examines how long the SARS-CoV-2 virus survives on skin and plastic. It investigates differences in survivability between the original Wuhan strain of the virus and subsequent variants – Alpha, Beta, Gamma, Delta and Omicron. The study claims to be the first to include Omicron in such side-by-side comparisons.

The researchers report SARS-COV-2 variants are able to survive on skin and plastic more than twice as long as the original Wuhan strain. Of particular interest, the Omicron variant was found to survive on plastic for 193.5 hours and on the skin for 21.1 hours. What is inferred is that this longer survival on these surfaces contributes to Omicron’s increased infectivity, because there is more likelihood of picking up viable virus from surfaces. But is that really likely?

The study has yielded interesting results but has limitations that mean understanding the significance of these findings to the real world is difficult.

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