Heart complications are often observed in severe or fatal cases of Influenza. These problems can include electrical malfunctions, scarring of the heart tissue, and even heart failure. This makes flu infections especially dangerous for individuals with a pre-existing cardiovascular disease. Elderly patients, already at an increased risk of severe Influenza infections, are also more likely to have a pre-existing cardiovascular disease.
Seasonal Influenza is a major contributor to human mortality. The CDC estimates that in the United States alone, there are up to 52,000 deaths and 41,000,000 infections annually. Though vaccines are effective in preventing the spread and lowering the severity of infection, research into Influenza remains important.
It was previously thought that flu complications related to the heart were a result of inflammation in the lungs. Scientists hypothesized that the degree of inflammation in the lungs was so severe that the entire body was strained, leading to heart problems in a subset of patients. Many scientists thought that cells in the heart were not directly infected by Influenza.
Researchers at the Ohio State University have demonstrated that Influenza infects cardiac cells along with infecting the lungs. The researchers genetically altered a strain of flu virus that was not able to replicate in heart cells and then infected mice with the strain. These mice developed classic flu symptoms—except for complications related to the heart. Post-infection, the mice infected with the genetically altered flu strain had less heart muscle damage, lower levels of injured cells, less scarring of heart tissue, and fewer problems related to electrical signaling in the heart.
This is the first time that scientists have shown flu-related heart complications are a direct result of the Influenza virus infecting heart tissue. The researchers hope to further elucidate the mechanisms by which the flu damages heart cells and determine whether repeated flu infections are more impactful.
Sources: Journal of Critical Care, Centers for Disease Control and Prevention, Science Advances