Researchers believe they now understand how severe flu cases cause heart damage, offering an explanation for the annual increase in heart attacks during flu season. As stated by Philip Swirski, the study leader from the Icahn School of Medicine at Mount Sinai in New York, «our study over the years has shown that the rate of heart attacks increases during the flu season, but... there has not been enough evidence on the mechanisms behind this phenomenon». By studying tissue samples from patients who died in hospitals from the flu, the researchers discovered that a type of immune cell becomes infected in the lungs and then travels to the heart. Instead of performing its usual immune function of removing the virus, the infected cells produce large quantities of a protein called type 1 interferon, which causes damage to heart muscle cells, leading to its weakening. As said Jeffrey Downey, a co-author of the study and also from the Icahn School of Medicine at Mount Sinai, in a statement: «These cells act as a 'Trojan horse' for the immune system during a flu infection, as the infection occurs in the lungs, the virus is transported to the heart and spread to heart muscle cells». The researchers confirmed in the medical journal Immunity that the flu vaccine provides some protection against this type of heart damage. Downey noted that in laboratory experiments, an mRNA vaccine, which in turn controls the activity of type 1 interferon, reduced flu-related heart muscle damage in test tubes and in a trial on mice and enhanced the muscles' ability to pump blood. Swirski stated that the new results «boost the chances of developing new treatments, which are desperately needed as there are currently no effective options for preventing heart damage caused by the flu».
