The arrival of sunny days does not reduce the infection itself

We found that an increase in UV radiation slows down the spread of the virus. The average daily UV radiation (UV radiation received by cities in our dataset is approximately between 30kJ / m² and 130kJ / m²) is reduced by R₀ 0.05 per ten kilojoules (kJ / m²) per square meter.

These results suggest a seasonal effect on SARS-CoV-2 coronavirus transmission as UV radiation levels are high during the summer. However, it is important to note that this correlation is not synonymous with causation: UV radiation does not necessarily cause a decrease in transmission, it is also associated with other causative factors. For example, if UV radiation is high in a city, it will be hot.

Although we cannot find a distinct and statistically significant relationship between R₀ and temperature or humidity at the overall level, we cannot exclude the existence of such relationships. The relationship between viral prevalence and temperature or humidity may be obscured by many other factors affecting R₀, as well as by the strong correlation between UV radiation and temperature.

Other studies have shown that there is a correlation between viral spread and temperature The evidence is weak.

What does that mean?

The effect of UV radiation we observed is statistically significant, although it is very small compared to other factors. The variations in R₀ values ​​we observed are further explained by the population characteristics of cities (such as their size and air pollution – the potential index of industrialization and congestion associated with population density), and public health. Measures taken to respond to infection.

It has been found that the effects of actions taken by governments in explaining variations in R₀ are four times greater than differences in terms of UV.

This means, and importantly, that our decisions put us in a position to keep ourselves in control. In the near future, the new waves of the epidemic will be determined mainly by the sanctions imposed by the governments, far beyond the weather. Added to this are the effects of the anticoagulant-19 vaccine.

In the long run, questions remain as to whether COVID-19 can become a seasonal local infection caused by influenza and other coronaviruses. Our research has highlighted the presence of seasonal factors that induce this type of variation, once Kovid-19 became an infectious disease in all likelihood.

However, it is difficult to predict that such behavior will occur in a system as complex as our planet. As we move out of the early stages of the infection, the long-term behavior of the Kovid-19 transmission certainly depends on many other factors. These include the level and duration of immunity acquired by infected individuals, as well as the effect and duration of protection provided by current and future vaccines, and the evolution of new viral variants.

Kieran Sharkey, Reader in Mathematical Sciences, University of Liverpool

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