Many of us have grown accustomed to the troublesome symptoms of influenza, but we rarely think about how serious the disorder can be except when we are reminded of the influenza epidemic following the First World War (which killed 20 million to 50 million people worldwide) or are frightened by the prospect of a bird flu epidemic.
In fact, influenza is a great threat every year, and the number of influenza-related deaths in the U.S. has increased significantly over the past 20 years (CDC researchers estimate that an average of 36,000 people die from complications of influenza each year in the United States).
It's also been recognized for a long time that more deaths occur in the winter months than at any other time of the year; and influenza is the major contributing factor to this greater mortality during winter. Fatal heart attacks are also about 50 percent more common in the winter than in the summer, and a recent study showed that influenza triggers many of these heart attacks.
Some studies have shown that more than twice as many people with influenza die as the result of heart attacks than from pneumonia or other complications of influenza. A fatal heart attack during or shortly after an attack of influenza is especially common among older individuals.
Researchers have proposed that influenza may trigger cardiovascular events by causing a general inflammatory state in the body and in the walls of arteries.
This arterial wall inflammation can then lead to rupture of an atherosclerotic plaque, which in turn promotes the formation of an artery-blocking blood clot.
Influenza should therefore be considered as a risk factor for a cardiovascular event, especially in those who are older than 65 or who have been diagnosed with cardiovascular disease or diabetes.
Since studies have shown that influenza vaccination halves the overall mortality rate from influenza, it is especially important for these people to remember to get an influenza vaccination this September, before the approach of the next flu season.