The undeserved stardom of flurone

In recent days we have witnessed an expected and worrying event according to the media: the coexistence in one person of two viruses at the same time, that of influenza and SARS-CoV-2. So much so that we already have a name for the new infection, flurone, which is in search and capture by the autonomies. Please do not confuse it with a heterocyclic chemical compound of the same name related to fluorescent compounds and pharmacological use, because it has nothing to do with it.
After two years of pandemic it was as if we waited for this to happen and confirmation had to come from abroad. From Israel specifically, although it seems that it had already happened even before in Spain. Although now it seems that it is a danger, the lion may not be as fierce as it is painted.
Before triggering the alarms we must ask ourselves if this fact is really important or just one more phenomenon that occurs and occurred long before the pandemic with a greater frequency than we think.
Possibly we will again have too much noise for so few nuts.
Respiratory viruses everywhere
More than two hundred viruses cause respiratory diseases in humans. There are not a few. Of these, most produce very similar symptoms such as sinusitis, pharyngitis, laryngitis, tracheitis, bronchitis, etc, etc … That is, respiratory tract infections that cause inflammation.
As for local inflammation, it only represents the activation of the immune system against viral infection, regardless of the virus it is.
A few years ago a study was done on viruses that live with us and that are located in the lungs and up to 19 different types were found. These viruses are the redondoviruses (you can imagine why they are called that) and do not cause disease unless our immune system is somewhat battered.
The relationship between virus and disease is relatively complex since everything depends on the severity of the symptoms they produce. In many cases, the symptoms are so mild that we don’t even appreciate them since the relationship between the virus and the immune system does not produce aggressive responses. In other cases even viruses are useful to prevent other diseases such as bacterial infections, since the cells they infect are not ours but bacteria and thus control the population of bacteria that could cause diseases. You know, that “the enemy of my enemy is my friend.”
The relationship between microorganisms and the immune system is established from birth. We are subjected to invasion by multiple microscopic organisms of bacterial or viral type from birth and our survival is determined by our body’s ability to keep them at bay. People who suffer from immunodeficiency know very well that not having an efficient immune system makes them a target of even the most innocuous microorganism. There we have the example of HIV patients and the recurrent and fatal diseases they suffered before antivirals arrived.
Flu viruses and coronaviruses are not the same
Since the beginning of the pandemic there has been some suspicion of the coexistence between the flu wave and the coronavirus wave. It is not because they are two viruses that are not similar, but because both can produce saturation of the health system separately, as they have already demonstrated.
Influenza viruses belong to the large family of orthomyxoviruses. In this family we have influenzaviruses A, B, C and D. Of these, the A and B cause the seasonal epidemic that visits us year after year (except last year thanks to social isolation measures). Specifically, influenza A is the one that causes pandemics while the B have less travel, the C create mild diseases and not considered pandemic and the D essentially affect livestock.
Flu viruses contain two important proteins in their membrane that characterizes them. This is hemagglutinin (H), which serves to infect cells by binding to a membrane sugar – sialic acid – and neuraminidase (N), which use the new virions to separate from sialic acid and infect a new cell.
In humans, 18 types of hemagglutinin and 11 types of neuraminidase have been characterized and their combination determines the type of virus that affects us year after year. Some combinations have proven very lethal, such as H5N1, but have not presented the ability to disperse among humans easily, for now.
Coronaviruses, however,go, they use another mechanism already known. Its Spike protein (S) binds to the ACE2 protein of the respiratory (including pulmonary) epithelium and thus infects the cells of the respiratory tract.
Another big difference between flu viruses and coronaviruses is their genome. While in influenza viruses the genome is made up of 8 pieces of negative RNA, that of coronaviruses is formed by a single strand of positive RNA. That assumes that the respective mechanism of genome replication is very different. In addition, in the remote event that both viruses infect the same cell, it is impossible for combinations of their genomes to occur that can give rise to a viable virus with hybrid characteristics. The possibility, if it existed, would be extremely remote and would be a real molecular surprise.
The real risk is in the symptoms it generates
The danger of co-infection with two aggressive respiratory viruses such as SARS-CoV-2 and a flu virus in unison would be found in the response to infection, i.e. in the symptoms. Seasonal flu is capable of producing thousands of annual deaths on its own even in vaccinated people, as their immune systems cannot stop the infection.
Therefore, if both viruses co-infect an immunologically depressed person, their combined action would generate already known symptoms such as pneumonia, cytokine storm and multi-organ failure that also occur in cases of influenza, respiratory syncytial virus, pneumococci and other respiratory pathogens separately.
Apart from this problem, which is already worrying, the other speculations about the recently baptized disease with such an ungraceful name should be considered nothing more than speculations without a solid scientific basis.
In any case, it should already be clear that to be prevented against influenza and SARS-CoV-2 infection, the best strategy is to strengthen the immune system with vaccination.
Guillermo López Lluch, Professor of Cell Biology. Associate researcher at the Andalusian Center for Developmental Biology. Researcher in metabolism, aging and immune systems and antioxidants., Pablo de Olavide University
This article was originally published on The Conversation. Read the original.

Original source in Spanish