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What particular characteristics do people who have never contracted Covid-19 have? Among the various hypotheses in the field, one is based on the so-called viral interferenceor “The growth inhibition of a virus caused by a previous infection”has explained to Republic Aureliano Stingi, molecular biologist and collaborator of the World Health Organization in the battle against fake news on COVID-19. Let’s see in detail what it is.
The concept of viral interference was first described in the 60’swhen i vaccines against the live enteroviruses (Lev), consisting of attenuated enteroviruses for the prevention of enteric diseases caused by a large number of unrelated pathogens, mainly in children. In addition to the protective effect of Lev on pathogenic enteroviruses, in particular on poliovirustheir vaccine administration in children reduced the detection of other unrelated respiratory viruses, such as influenza virus, parainfluenza virus, RSV, HRV and human adenovirus.
How remember from the Centers for Disease Control and Prevention (Cdc), we know that different respiratory viruses can circulate during the same period and infect our respiratory tract simultaneously or sequentially, thus creating virus-virus interactions, which can be “positive“, ie synergistic, or “negative”, That is, antagonistic. In the first case, these are co-infections that could lead to an increase in severity of the disease, while in the second case, the negative ones, there may be two other possibilities: homologous and heterologous, depending on whether the two viruses belong to the same family or not. It goes without saying that the homologation implies that theimmunity against a first virus it also prevents infection against a second virus. Heterologous viral interference, on the other hand, is based on the induction of one innate immune response it is not specific by a first virus that reduces or prevents the infection and replication of a second virus, such as influenza A virus and respiratory syncytial virus. “The type of virus-virus interaction (negative or positive) probably depends on the respiratory viruses involved, the timing of each infection and the interaction between the host response to each virus”explain from the CDC.
Take for example the coronavirus and the flu virus. In the past seasons, in fact, when the infections from COVID-19 peaked we observed that cases of influenza were significantly reduced. And this could be due to a competition between viruses, or rather to viral interference, based precisely on the control of one virus on the proliferation and, therefore, spread of the others. The most probable biological mechanism of this phenomenon is based on interferonsthat is the group of proteins that are produced by the cells of the immune system to defend themselves from the attack of a virus and which serve, therefore, to induce protection against pathogens, which is in any case transient.
In the case of influenza and Covid-19, they specify from the CDCs, more research is needed to clarify the interactions between SARS-CoV-2 and the flu virus. Early studies, however, seem to show that “The innate immune responses induced by Sars-Cov-2 and the influenza virus in the upper and lower respiratory tract could influence the type of virus-virus interactions, depending on which virus it infects first”explain from the CDC. “L’viral interference at the population level it is difficult to prove since there are differences in the dynamics of transmission of respiratory viruses based on social behaviors and the time of year between the various age groups ”.
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