Influenza A virus suppresses the reproduction of SARS-CoV-2

(ORDO NEWS) — Both the novel coronavirus SARS-CoV-2 and the influenza A virus cause dangerous and widespread respiratory tract infections.

Not surprisingly, both pathogens sometimes infect the same person – this is the so-called coinfection.

Influenza A virus suppresses infection caused by SARS-CoV-2 (the causative agent of Covid-19), according to a study in cell cultures and rodents.

The long two and a half years of life in a pandemic has become a real test for both the healthcare system and ordinary people.

This time also gave rise to many concerns about the danger of other pathogens and, say, combined infections – when infected with SARS-CoV-2 and some other virus.

Previously, similar studies have been carried out for HIV, hepatitis B and C viruses, dengue virus and, of course, influenza.

In fact, in the first few months of the pandemic, doctors recorded a significant number of people infected simultaneously with SARS-CoV-2 and the influenza A virus.

They accounted for three percent of the total number of cases of Covid-19. Such cases were considered more severe and dangerous, and later similar results were obtained in experiments on mice.

Both SARS-CoV-2 and influenza A virus are primarily airborne, affect the respiratory tract, and can cause severe acute respiratory syndrome (SARS).

At the same time, these viruses belong to different families and use different receptors on its surface to penetrate into a human cell: the angiotensin-converting enzyme ACE2 in the case of coronavirus and polysaccharides with sialic acid at the end in the case of the influenza pathogen.

However, their tropism, that is, specificity to certain tissues, largely coincides: both viruses infect the lungs, primarily alveolar cells of the second type – in this sense, the viruses compete with each other for lung tissue.

To find out the details of the interaction between SARS-CoV-2 and the influenza A virus that got into the same cell or organism, the authors of a new article in the Journal of Virology used different model systems: cell cultures, as well as Syrian hamsters, rodents that reproduce human infections well.

Both cells and animals were individually infected with SARS-CoV-2, the causative agent of influenza A, as well as both viruses. In some cases, one infection preceded another.

As a result, it turned out that, contrary to expectations, coronavirus does not make the course of infection with the influenza virus more severe – in fact, SARS-CoV-2 does not affect the influenza A virus infection cycle in any way.

However, much more important was the influence of a previous infection with the influenza virus on the replication (creation of new copies) of SARS-CoV-2.

It was shown that the coronavirus infection in this case was suppressed, and the copying of the SARS-CoV-2 genome was slowed down, which is associated with the specifics of the interaction of this pair of viruses. Moreover, the effect is observed, even if a week has passed since the moment of infection with the flu.

According to the authors, the new data suggests that the simultaneous infection of influenza A and SARS-CoV-2 – two respiratory viruses that can cause pandemics – “should not be considered as a huge threat looming over humanity.”

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