A preclinical study in animals has found that, in pregnant women, the flu virus does not only affect the lungs, but it spreads throughout the body, which can cause significant complications and endanger the life of the pregnant woman and fetus.

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The study, published this Monday in the journal Pnas, is of great importance not only for pregnant women and their babies, but it could help scientists to understand the biological functioning of Covid-19 and how it spreads from the lungs to the rest of the body.

The research, led by the RMIT University of Melbourne (Australia) and carried out in animal models, showed that during pregnancy the flu spreads from the lungs through the blood vessels to the circulatory system and triggers a harmful overactive immune response.

The focus: the vascular system

The study results suggest that the vascular system is the focus of the serious complications that the flu can cause during pregnancy.

Until now it was thought that the problems were related to the weakness of the immune system during pregnancy, but it has been proven that “the opposite occurs: influenza infection leads to a dramatically elevated immune response“explains Stella Liong, RMIT researcher and lead author of the work.

“The inflammation in the circulatory system is so overwhelming that it is like a vascular storm that wreaks havoc throughout the body.”

“The inflammation in the circulatory system is so overwhelming that it is like a vascular storm that wreaks havoc throughout the body“, said Liong.

Although the researchers acknowledge that further research will be needed to validate the study results, “the discovery of this new mechanism will be a crucial advance in developing therapies designed specifically for pregnant women, “says Liong.

“A historical advance”

For his part, John O’Leary, a researcher at Trinity College Dublin and co-author of the study, affirms that the work is a “historical advance”.

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“The discovery of a flu-induced ‘vascular storm’ is one of the most significant advances in inflammatory infectious diseases of the last 30 years and has important implications for other viral infections, including Covid-19 “, he emphasizes.

The study reveals that the flu not transmitted directly from mother to baby, although its potentially devastating effect on women is closely related to complications suffered by the fetus (miscarriage and premature birth).

Intense inflammation with serious consequences

The research, based on the influenza A virus, showed that the virus behaves in a very different way in the bodies of pregnant mice and those that were not.

In non-pregnant women, the virus remained localized in the lungs, while in pregnant women, it spread to the circulatory system through blood vessels, causing a intense inflammation with serious consequences in the function of the great blood vessels, in the health of the mother and the blood flow to the fetus.

The study found that pregnant mice with the flu had severe inflammation in the large blood vessels and aorta. Thus, while a healthy blood vessel dilates between 90 and 100% to allow blood to flow freely, blood vessels infected by the flu functioned at only 20-30% of its capacity.

“We found a dramatic difference in these inflamed blood vessels, which can seriously affect the amount of blood that reaches the placenta and all the organs that help support the growing baby, “concludes Stavros Selemidis of RMIT.