The possibility that the hot season will reduce the infection or weaken Sars – CoV – 2 has already been discussed and confirmed by some research. But the study conducted in Milan in collaboration between immunologists and astrophysicists has allowed us to demonstrate that it is the specific factor of solar radiation that has the ability to neutralize the coronavirus in saliva droplets, the famous “droplets” that spread the infection. Published in preprint on the medrxiv international archive, in the section dedicated to Covid-19, the two articles (to which a third is about to be added) are the result of the work of researchers of the IRCCS Don Gnocchi Foundation in Milan, of the University of Milan , the National Institute of Astrophysics and the National Cancer Institute.
“The sun sends photons to Earth,” he explains Mario Clerici, professor of Immunology at the University of Milan and scientific director of the Irccs Santa Maria Nascente presidium of the Don Gnocchi Foundation – under three wavelengths of ultraviolet rays: Uv – A, Uv– B, Uv – C. The latter are blocked by ozone in the atmosphere and do not arrive on Earth. They are used, for example, by lamps for the sanitation of aquariums because their sterilizing power on viruses and bacteria is known. So we asked ourselves if the UV-Cs would have been able to inactivate Sars-CoV-2 in the saliva droplets that transmit the infection ». The experiment it consisted in growing the virus and spreading it in suspended water droplets, then exposed to different doses of UV-C. “Also of the virus – continues Clerici – we have spread three quantities in the droplets: the dose that is detected in infected but asymptomatic subjects, then multiplied by ten, which is detected in the swab of a patient with symptoms, and then for a thousand, that present in a dying patient from Covid pneumonia – 19 “. The outcome was positive: «We found that a small dose of Uv – C, equal to 3.4 millijoules per square centimeter, is enough to completely inactivate the virus, even at the highest doses: just less exposure than the irradiated one from lamps used to disinfect aquariums. It is the first demonstration that UV-C works, and that the quantity needed is minimal. Then we repeated the experiment with the Uv – A and Uv – B, who instead reach Earth, and the result was the same ».
This seems to justify the fact that the pandemic “now appears more controlled in the countries of our hemisphere, while it is growing in the southern one (for example Brazil), which is going to face the winter. And the phenomenon is confirmed by the comparison we made between the data of solar radiation in 246 countries of the world between 15 January and 30 May, collected by the Temis agency, and those of the prevalence of Sars-CoV-2 infection released by the World Health Organization. We have seen that there is an almost perfect relationship between the two data: as the amount of solar radiation increases, the number of new infections decreases. Of course, the containment measures adopted (spacing, masks, etc.) also affect, but astrophysicists have found that the factor that really makes the difference is the amount of solar rays that arrive on Earth ». However, Clerici points out, it is difficult to make predictions about the future: «We cannot say whether the virus will return or not. Sars 1 has disappeared, Mers has not. It is possible that in autumn the cases increase, but we are much more prepared to deal with the infection than it was in February-March ».
A comparison with the flu offers some hope: «Every year your RNA virus has a minimal genetic change, which does not allow you to immunize yourself forever, but even if you do not reach flock immunity (only 10-15%) it disappears and reappears. Our third research, currently being published, notes that in the last 120 years the epidemic trend of influenza is inversely proportional to solar radiation “.