Flurona: what is the double infection of influenza viruses and covid-19

Since the beginning of the pandemic, there has been some suspicion of the coexistence between the flu wave and the coronavirus wave.

Photo: Andrea Piacquadio / Pexels

In recent days we have witnessed an expected and worrying event according to the media: the coexistence in a person of two viruses at the same time, that of influenza and covid-19, which was baptized as “flurone”.

After two years of pandemic, experts assure that this combination was confirmed in Israel, although apparently it had already happened before, even in Spain.

Although it now looks like it could be a dangerous situation, it may not be that serious; First, it must be analyzed whether this fact occurred since the beginning of the pandemic, or more frequently than we imagined.

Respiratory viruses in humans

More than two hundred viruses cause respiratory diseases in humans; Most of them produce very similar symptoms such as sinusitis, pharyngitis, laryngitis, tracheitis, bronchitis, among other diseases.

A few years ago a study was made on viruses that live with us and that are located in the lungs and up to 19 different types were found.

These viruses are roundviruses and they do not cause disease, unless our immune system is weak; 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 do not 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.

Flu and covid-19 proteins

Influenza viruses contain two important proteins in their membrane that characterize them:

It is hemagglutinin (H), which serves to infect cells by binding to a membrane sugar (sialic acid) and neuraminidase (N), which are used by 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 been shown to be very lethal, such as H5N1, but they have not shown the ability to spread easily among humans, for now.

Coronaviruses, however, use another well-known mechanism. Its Spike (S) protein binds to the ACE2 protein of the respiratory epithelium (including the lung) 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 made up of a single strand of positive RNA.

This assumes that the respective genome replication mechanism is very different.

In addition, in the remote assumption that both viruses infect the same cell, it is impossible for combinations of their genomes to occur, which can give rise to a viable virus with hybrid characteristics.

The possibility, if it existed, would be extremely remote and would come as a true molecular surprise.

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 similar viruses, which they are not, but because both can cause saturation of the health system separately, as they have already shown.

Influenza viruses belong to the large family of orthomyxoviruses. In this family we have influenza viruses A, B, C and D.

The real risk is in the symptoms

The danger of co-infection with two aggressive respiratory viruses such as SARS-CoV-2 and an influenza virus at the same time would be found in the response to the infection, that is, in the symptoms.

Seasonal flu is capable of causing thousands of deaths annually by itself, even in vaccinated people, since their immune systems cannot stop the infection.

Therefore, if both viruses co-infect an immunologically depressed person, their combined action would generate known symptoms such as pneumonia, cytokine storm and multi-organ failure that also occur in cases of influenza, respiratory syncytial virus, pneumococci and others respiratory pathogens separately.

In any case, it should be clear that to be prevented against flu and covid-19 infection, the best strategy is to strengthen the immune system with vaccination.

Also read:
· “Flurona”: the simultaneous flu and COVID-19 contagion that had its first case in a pregnant woman from Israel
IHU: They discover a new variant of Covid-19 with more mutations than Ómicron
Ómicron has led many US companies to delay going back to office


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