SARS-CoV-2, commonly known as Covid-19, is a novel coronavirus first identified in Wuhan, China in late 2019. It is a member of the family of coronaviruses that includes Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). The virus is thought to have originated in bats, and is spread mainly through close contact with an infected person through respiratory droplets, such as sneezing and coughing. There is open scientific discussion as to whether the virus may have escaped from a research lab. ^{1) 2)}

The symptoms of Covid-19 vary from mild to severe, and can include fever, cough, and shortness of breath. In more severe cases, the infection can lead to pneumonia, severe acute respiratory syndrome, kidney failure, and even death. Several treatments and prevention measures that can help patients to recover faster in case of infection are currently available.

The World Health Organization declared Covid-19 a pandemic on March 11, 2020. Since then, the virus has spread rapidly, resulting in over 20 million confirmed cases. In countries where this new disease was not cured correctly and in a timely manner many thousands of people died.

Scientific studies have confirmed that in countries or regions where vitamin D deficiency in the population is widespread the severity of symptoms and mortality rate has been the highest.

This virus, as other coronaviruses, has a high rate of mutations, so during time the following variants of the virus have been classified. For this reason the epidemy had several waves:

Currently the older strains do not circulate anymore because they have been replaced by Omicron variants and derived descendents, which are milder and have higher contagiousness, also among people that received artificial immunization, because of the high pace of mutation of the virus. These new variants have a big evolutionary advantage compared to the original version of the virus.

A Danish cohort study demonstrates that breakthrough infections can not be avoided. Artificial overstimulation of the immune system with older strains can even lead to negative protection, aftern some months, when new variants emerge. ³⁾

A new study on mice confirmed that repeated artificial immunization overturned the protective immune memories by promoting adaptive immune tolerance. This means that there can be risks with the continuous use of boosters. ⁴⁾

It has been demonstrated that that natural immunity given by healing confers longer lasting and stronger protection against future infection and symptomatic disease. ⁵⁾

Current Omicron variants cause much fewer risks than Delta strains, with symptoms that generally remain in the upper respiratory tract. Currently Omicron infection is less dangerous than seasonal influenza. ⁶⁾

A high percentage of the world population has currently aquired natural immunization after encountering one or more variants of the virus, therefore it can be considered that this type of infection has become endemic like traditional flu and will be recurrent in the following years. Omicron has worked as a natural immunizer and this is helping to reach herd immunity. ⁷⁾

Natural way for preventing severe illness are now known, first of all it is important to avoid vitamin D deficency. ^{8) 9) 10) 11)}

Currently there is also a lot of experience in the medical community regarding correct treatment of patients. ^{12) 13) 14)}