Rijeka immunologist: Korona has not weakened, a more difficult scenario may await us in the coming weeks

ZLATKO TROBONJAČA, an immunologist from the Medical Faculty of the University of Rijeka, explained what exactly the weakening of covida-19 means and why the coronavirus has not yet taken a milder form.

“Has the SARS-CoV-2 virus weakened? How could the weakening of the virus manifest itself at all? The weakening of the virus could be manifested by a disease with milder symptoms and more favorable outcomes, meaning fewer disease residues and lower mortality. This can indeed happen if the virus would be better adapted to human biology and the biology of the cells in which the virus multiplies, which would mean that it does not have a strong cytopathogenic effect, does not cause cell death and develops mechanisms to avoid or subvert the immune system, “explains Trobonjača.

A milder form is in the interest of the virus itself

“It would also mean that the infection could pass with less damage and without the death of the host. In the long-term evolution and life cycle of the virus it is a benefit and an advantage because in that case the virus would be harder to recognize, attack and eliminate by immune mechanisms. the other side by surviving the host had more time and more chances to switch to another individual.

For example, some viruses are difficult to spread in the human population because they are too aggressive, causing severe disease and death of the host before they can pass to another individual. This evolutionary adaptation occurs on the basis of mutations in the viral genome, creating viral forms more resistant to the action of selection pressure and thus gaining an advantage in the life cycle over less adapted viral forms, with better adapted forms surviving and less adapted ones decaying. It is basically the foundation of the evolution of all living things, including viruses. Therefore, it is obvious that the dynamics of evolutionary adaptation is directly related to the dynamics of mutations in the genome of the virus, “writes the epidemiologist.

“Coronavirus has not weakened so far”

“The SARS-CoV-2 virus mutates relatively slowly. Isolated forms of the virus have a maximum of thirty mutations compared to the original Wuhan virus, and forms from the Croatian population ten to fifteen (nextstrain.org). This is practically negligible in viral evolution, especially if these mutations affect those parts of the viral genome that are not important for the virus replication cycle.

SARS-CoV-2 is a zoonotic virus, ie it is characteristic of animals and relatively poorly adapted to human biology, which is why it causes a kind of “strange” disease. With this dynamics of SARS-CoV-2 virus mutations, it would probably take tens or hundreds of years (if not more) to circulate among individuals for evolutionary adaptation to human biology, and it is impossible to expect this to happen in a few months. Therefore, the SARS-CoV-2 virus did not “weaken”. The virus is the same, and we are the same, so the COVID-19 disease is the same as it was a few months ago, “Trobonjača wrote on Facebook.

“It is not good to cause excessive panic among people, but it is not good to over-relax them with unfounded information about the weakening of the virus. This can result in unnecessary relaxation of citizens and the spread of epidemics. The impression of weakening the virus may be due to from milder forms of the disease or the fact that complications have not yet developed in infected individuals in this second wave, which usually takes seven to ten days (or more) from the onset of the disease.

Therefore, in the coming weeks we will most likely witness severe clinical forms of this disease and adverse outcomes especially among our elderly and chronic diseases affected fellow citizens. That is why caution and all epidemiological measures are still extremely important to avoid infection, ”concludes the immunologist.

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