Coronavirus turns into a seasonal illness with severe exacerbation in winter

“Our model offers a simple answer to a number of important but still unresolved scientific questions,” explains

Fabrizio Nicastro, INAF researcherand project manager. “Why do many viral respiratory epidemics—such as influenza—develop cyclically in the fall and winter only in temperate regions in the northern and southern hemispheres of the globe? In this case, infections are constantly present, but are less common in the equatorial belt? What generally causes and determines such seasonality? We found that the reason for the seasonality of airborne epidemics is the amount of daytime solar radiation on the Earth.”

It is well known that ultraviolet lightcapable of deactivating viruses and bacteria of various types. Therefore, the solar UV light that reaches the Earth should also have some disinfecting ability on the exposed parts of the planet. Of course, the effectiveness of UV decontamination depends on the type of virus or bacteria.

However, in temperate regions of the EarthDue to the climate in the northern and southern hemispheres, this process also depends on the time of year. Solar radiation (and, therefore, UV deactivation of viruses) is stronger in summer and lower in winter.

This is the “scheme” of solar disinfectioncorrelates with other cycles typical of epidemics. Namely, the loss of immunity of the host of the virus due to its antigenic drift. The combination of these two mechanisms causes the seasonality of epidemics, scientists are sure.

The model proposed by the Italianresearchers, accurately reproduces the seasonality observed in different parts of the Earth for epidemics with a reproductive number (R0) below two (for influenza, usually R0 ~ 1). In addition, the experts were able to simulate epidemics with a much higher R0. These include the current SARS-CoV-2 pandemic with a reproductive number in the region of 3-4. Ultimately, scientists predict high-intensity, intermittent initial COVID-19 cycles that will eventually stabilize at seasonally synchronized, moderate intensities.

In other words, the model of Italian scientists predicts the constant presence of the coronavirus with a seasonal flare-up in winter.

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