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Provisional research, subject to peer-review and assessment by experts, on the environmental factors linked to the spread of COVID-19 suggests that ultraviolet radiation (UVR), temperature and humidity are factors affecting the spread of the SARS-CoV-2 virus.

A study entitled Nocturnality, seasonality and the SARS-CoV-2 Ecological Niche and posted as a preprint on Cornell University’s arXiv server looked at Italy, Spain and Australia for a nine-week period following lockdown and found that the number of reported cases of COVID-19 decreased as natural ultraviolet radiation increased. High temperatures and humidity enhanced the effect. The researchers linked these results with the behaviour of coronavirus-carrying bats and suggest that those features of bat behaviour, particularly nocturnal behaviour and living in caves and in large groups, are the long-term evolutionary features that have characterised coronaviruses over millions of years of coevolution with bats. The authors stress that lockdown has been the key overriding factor in flattening the disease growth curve and that the influence of the environmental variables identified must be seen in a co-evolutionary context and as providing the backdrop. They stress that the lesson could be learnt from the behaviour of bats. Human activities resembling those of highly social cave-dwelling bats will only serve to exacerbate the problem. Thus nocturnal gatherings or high-density indoor activities, for example, should be avoided. The authors of the research include scientists from the Gibraltar National Museum, Gibraltar Botanic Gardens and the University of Gibraltar as well as scientists from the Universidad de Murcia, University of Toronto and the Instituto de Salud Carlos III in Madrid. The authors emphasise that they have brought their results forward so as to enable experts to assess these quickly. These results should, therefore, currently not be relied upon without context to guide clinical practice of health-related behaviour and should not be reported in news media as established information without consulting multiple experts in the field.


Access the preprint via ResearchGate.



Finlayson, G., Finlayson, S., Finlayson, C., Bensusan, K., Guillem, R., Holmes, T. L., Giles Guzmán, F., Carrión, J. S., Belda, C., & Sawchuk, L. (2020). Nocturnality, seasonality and the SARS-CoV-2 Ecological Niche.

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