How much virus?

The most important limitation of the study, and one that is shared with similar survivability studies published earlier in the pandemic, is generalising survival times in the laboratory to survival times in the real world. The main reason for this is the lack of a clear rationale for the decision on the amount of virus added to the surfaces tested.

This is important because the ability to detect viable virus on a surface over time is hugely influenced by the amount of virus seeded on the surface in the first place. Theoretically – and not to suggest the researchers in this study did this – you could contrive any survival time in the laboratory if you deposit enough virus at the outset.

How the amount of virus used in this study relates to how much virus might be deposited on a real world surface by an infected person is not clear from the preprint article.

The laboratory versus the real world

It’s also worth noting the study was completed under highly controlled laboratory conditions. It is reasonable to speculate real world conditions would be harsher and more changeable – in terms of temperature and humidity – which may reduce virus survival times considerably.

On the plus side, researchers used the same set of conditions when assessing all variants so comparisons of survival times are likely to be a good indicator of relative environmental stability. Therefore the increased survival time of the Omicron variant compared to other variants is likely to indicate mutations that make it more resilient. This could contribute to its increased infectiousness – but the extent of any increase in the amount of surface transmission, the relative contribution of surface transmission to Omicron infections, and what causes this enhanced environmental stability are key questions that were beyond the scope of the study.

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Originally Appeared Here