The sun’s rays make the Covid fall.

La solution la plus avancée en matière de décontamination

The sun’s rays make the Covid fall.

An Italian study about to be published shows how ultraviolet rays ‘kill’ Covid-19: ‘A minimal dose of these rays, in a very short period of time, is able to completely inactivate Sars-Cov-2’.

There are many reasons why we should be optimistic and positive today, but not Covid positivity, on the contrary: several studies, including an Italian one that is about to be published, confirm what we already “guessed” last summer, namely that sunlight inactivates Covid-19.

Astrophysics and virology together

There is strength in numbers: two apparently distant fields have come together, astrophysics and the study of viruses and virology. “It all started in March 2020 when the Ministry of Universities and Research (Mur), invited all research organisations and universities to make their expertise available to fight the pandemic. The president at the time, Professor D’Amico, who unfortunately passed away, appointed me as national coordinator and we started with what we know best, the knowledge of light, and we were lucky enough to collaborate with the University of Milan through the group led by the professor. We were lucky enough to collaborate with the University of Milan, with the group led by Professors Clerici, Biasin and Trabattoni, in order to carry out experiments immediately and implement different skills,” Giovanni Pareschi, director of the INAF (National Institute of Astrophysics) at the Brera Astronomical Observatory in Merate, in the province of Lecco, told exclusively. With some surprising results, changes were observed in the Sars-Cov-2 virus when exposed to sunlight but also to artificial light.

The effect of UV-A, UV-B and UV-C radiation on Covid

“We focused on two particular aspects: the disinfection of the virus with the so-called UV-C radiation from the blue lamps inside the aquariums, a very powerful and effective method, but unfortunately still little used in Europe to disinfect the air in closed environments”, Prof. Klaus Schmidt. Pareschi, explaining that the means of contagion of the virus are essentially three: direct contact (when talking about proximity), surfaces and aerosol, which remains in suspension even for hours inside closed environments and the only way to combat this form of contagion is through air renewal. “In this case, UV-C lamps are very effective but have not been widely adopted in public environments, schools, etc. The other aspect we focused on – adds Pareschi – is that UV-C radiation is emitted by the sun but does not reach the Earth because it is absorbed by the tropospheric ozone layer. In practice, it is the only type of radiation that can be used artificially and not naturally.

What happens in summer

“However, the UV-A and UV-B components of the solar spectrum still reach the Earth’s surface. “We set out to understand whether and how solar irradiance relative to these spectral components can moderate the pandemic.” The research, which began in May 2020, is still ongoing, but already, at the beginning of last summer, “based on preliminary data and studies, we predicted that the pandemic would be seasonal, with waves, long before what then actually happened,” explains the astrophysicist. And the result of the studies is particularly important because “it appears that this virus, which has RNA, is particularly susceptible to being inactivated by solar radiation that reaches the Earth through both UV-A and UV-B. This means that in summer, both because of the sun’s rays and because the saliva bubbles emitted by people evaporate easily, if you are in an environment populated by people who are spaced out, the aerosol can be annihilated in a few tens of seconds in broad daylight. The professor gives the example of a beach where this phenomenon is even more pronounced thanks to the reverberation of the sand which amplifies the effect. “We therefore establish a link between seasonality and the presence of UV-B and UV-A solar radiation.

What happens on the immunological level

If from the astrophysical point of view we have clearer ideas, what happens from the immunological point of view? The results are almost identical and have also been observed clinically in lung cells. “Last year we published the ability of UV-C radiation to almost completely inactivate the virus, but it is filtered out by the ozone and does not reach the Earth’s surface. We have now extended this data with a preprint ready for publication where we show that using also UV-A and UV-B rays, the ones that reach the Earth’s surface and redden the skin as well as the ones that we buy tanning, a very small dose of these rays, in a very short period of time, is able to inactivate Covid-19 completely. If you look at the virus under the microscope and put it on a carpet of lung cells, you can see that with a minimal dose it is no longer there, it disappears, you can see its absence”: this is what Mario Clerici, Professor of Immunology and Immunopathology and Director of the Department of Physiopathology and Transplantation at the State University of Milan, said exclusively to

“Sunlight changes the genetics of viruses.”

The hypothesis of some Scottish researchers (here their study) is that exposure to UV-A stimulates the production of nitric oxide, which has antiseptic properties and may reduce the ability of Sars-Cov-2 to replicate. “I am quite sceptical: UV-A, directly, is already able to block the virus because it modifies its genetic base. There is no need for such a complex mechanism, because what happens with the sun’s rays is already sufficient,” explains Professor Clerici. But that’s not all: ultraviolet rays also activate the synthesis of vitamin D “which is a powerful stimulus for the production of B and T lymphocytes, in this way we increase the immune response to the virus but even this explanation is not necessary and adds a level of complexity to a phenomenon that in itself is simple. UV-A and UV-B rays, directly, prevent the virus from replicating because they damage its genetic structure,” says the immunologist.

What happens in autumn and winter

The sun is there all year round, the sun’s rays always arrive but they become less effective when our hemisphere is in autumn and winter. “This is where our expertise as astronomers comes in – explains Pareschi – it happens simply because the flux is less, mainly because of the reciprocal positioning between the Earth and the Sun, and arrives much less. The positioning between the Earth and the Sun is such that the decrease is, depending on the position of the globe, up to a factor of about 10 less”. In addition, the expert tells us that one of the most important results being published concerns ultraviolet radiation to Covid. “This Rna virus seems to be much more susceptible to inactivation by UV-A radiation than other viruses, notably Dna viruses. This tells us that it is much more sensitive to solar radiation than others.”

Why does the virus kill in “hot countries”?

Beware, however: the more attentive may point out that in Brazil, where the weather is practically year-round and the sun’s rays are always plentiful, the pandemic continues to rage and claim victims because of another climatic factor that, in fact, cancels out the benefits of ultraviolet light. “Humidity matters a lot: where there are clouds and a humid climate, even in summer, seasonality is less pronounced: Brazil is a very large nation and there is a big difference between Rio de Janeiro and the Amazon: studies done on influenza have shown how an epidemic decreases very quickly in the Rio area but remains in the Amazon where there is a much more humid climate,” explains Professor Pareschi. The question arises: when we read that heat and sun weaken the virus, is this not true? “Often words are used inappropriately: summer, at latitudes like ours, is linked to an increase in ultraviolet rays, on this aspect we are sure and we think that they are one of the factors that inactivate the virus. Heat, on the other hand, is very generic: in itself it does nothing, the virus survives up to 70 degrees, but it needs water, the famous saliva bubbles. Heat can contribute to the evaporation of these bubbles by acting indirectly, while ultraviolet rays are a direct factor: we see all this with incredible efficiency in the experimental tests, they also amaze us. We did not expect ultraviolet A and B to be so effective,” explains the astrophysicist. The message is clear: one thing is the open-air beach, spaced out, another is a disco where you are all gathered: it is logical that in this case the virus can be transmitted, and the examples we had last summer did not need astrophysical or epidemiological studies.

How important is vitamin D?

The sun’s rays, however, in addition to killing the Covid in a very short time and giving us a tan, cause the stimulation of vitamin D which our body stores during the summer season and thanks to which we “live” for some months. How does all this affect Sars-Cov-2 disease? “If we link exposure to UV-A and UV-B to an increase in the synthesis of vitamin D, which is a stimulant of the defensive response (antibodies and lymphocytes), in autumn we have a better functioning immune system because we bring in greater amounts of vitamin D that have been synthesised with exposure to the sun,” explains Professor Clerici. There are those who say that the virus affects anyone and those who say that if you have higher amounts of vitamin D, you can somehow avoid a greater degree of illness.

Is vitamin D from sunlight different from vitamin D in food or pills? “He hit the nail on the head”, smiles the epidemiologist, “vitamin D synthesised from skin precursors following exposure to UV-A and UV-B rays and is qualitatively better than what can be taken with a pill, among its effects, there is a better stimulation of the immune response. So not everything is equal. “The vitamin D that the body produces spontaneously works better than the vitamin D that can be taken from tablets rather than from vitamin D-rich foods. The one produced by the skin is more effective, but there is no experimental data that shows with certainty that high doses of vitamin D defend us better against Sars-Cov-2. It is presumed, but there is no solid, indisputable data to prove it”, he stresses, without giving false hope to those who, for months, have continued to say that vitamin D “protects” against Covid.

“Vitamin D can help, for example, if you have a cold sore, which is not such a serious infection. But with the more difficult ones like Sars-Cov-2, it’s not enough to make a difference. Basically, the only way to beat the pandemic is to vaccinate: whatever kind of vaccine they give us, let’s do it. Also, because no one knows that serious side effects between vaccines are no more common at AstraZeneca than at Pfizer…”, concludes Clerici.

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