Scientists have found a secret "back door" through which influenza viruses enter cells

Scientists have discovered a hitherto unknown way for influenza viruses to enter the human body. These secret "back doors" allow infectious agents to enter human cells.

According to the scientists, influenza viruses that are able to use the second cellular entry point can move more intensively between animals and humans. And this is an additional risk of infection, LiveScience writes.

Seasonal influenza viruses "attack" about 1 billion people every year. Typically, they enter human cells by binding to sugar molecules called sialic acids on the cell surface. This starts a process that moves the virus into the cell where it can replicate.

Similar to human influenza viruses, many influenza viruses that infect animals use sialic acids to enter host cells. However, it turned out that some use a different entrance called the major histocompatibility complex class II (MHC-II). Scientists have speculated that there may be influenza viruses that use both of these pathways.

In a new study, scientists have found that those viruses that enter the body through a different route can multiply faster and reach higher levels in human lung cells than viruses that only use the "front door".

The main concern is that not only do human influenza viruses enter our cells this way, but that animal influenza viruses may use the same pathway. For example, avian H2N2 is an avian influenza virus that caused a pandemic in the 1950s after it swapped genes with the human H1N1 virus.

"Today, H2N2 viruses no longer circulate among humans, but live in the avian reservoir. But given that people born after 1968 did not come into contact with H2N2 viruses and therefore have no immunity against them, avian viruses could cause a new wave of pandemic," said Umut Karakus, author of the study and researcher at the University of Zurich.

The H2 virus can infect pigs, mice and ferrets, as well as a variety of birds. This ability to cross species and share genes with other influenza viruses raises the possibility that H2N2 could someday be transmitted from animals to humans. If such viruses become able to spread easily between people, they could cause a pandemic.

But don't panic just yet. Scientists will be conducting a series of studies to better understand the nature of the spread of viruses. With a better understanding of how these viruses behave in the wild, scientists will be able to draw more accurate conclusions about where the greatest risks are and how to prevent the next flu pandemic.

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