Flu season is upon us once again, and so the question of whether or not to be vaccinated against it also comes up again. The influenza virus in its pandemic forms can be very serious (in the U.S. alone, 200,000 people are hospitalized and 36,000 die from the flu per year), but even in its relatively benign forms the flu can produce symptoms such as chills, body aches, fatigue, coughs and sneezing, headaches, and high fever. On average, 5 to 20% of Americans experience these or similar symptoms every year when they get the flu, so trying to avoid them is a persuasive argument for being vaccinated.
But now you can add another argument to the "Yes" side of the "Should I get a flu shot?" question – the potential long-term side effects or impact of contracting influenza. Recent studies have suggested that the flu virus may be linked to both diabetes and heart attacks.
The flu-diabetes connection
Researchers in Italy, working at the World Organization for Animal Health laboratory that studies the impact of avian (bird) flu, examined the effects of the flu virus on the pancreas in animal studies, and also on human pancreatic tissue. People who contract Type 1 diabetes have an inherited genetic predisposition for the disease, but for it to appear and begin attacking the pancreas, there also usually needs to be some kind of environmental trigger. In their studies, the Italian researchers found evidence that the flu virus may be at least one of those triggers.
The presence of the flu virus in pancreatic cells seems to trigger the production of a number of inflammatory chemicals central to the autoimmune reactions that create Type 1 diabetes. The flu virus is normally found in the lungs and stomach, but can also appear in blood, which would route it to the pancreas. Once there, the virus "finds a good place to replicate," possibly because the same immune bodies that attack the flu-infected cells may begin to attack the cells that produce insulin. Researcher Ilaria Capua suspects that the widespread H1N1 swine flu epidemic of 2009 may be one of the causes of the huge increases in diabetes we've seen worldwide since.
Other researchers in Italy and Japan tend to agree, citing an increase in the number of children diagnosed with Type 1 diabetes who had previously contracted influenza. During the winter season of 2004-5, the flu virus was found in the bloodstreams of only 7% of children treated for diabetes. But during the winter of 2009-2010 (after the 2009 pandemic), the flu virus was found in 21% of the diabetes patients. The researchers concluded that "The 2009 H1N1 virus seems in some way involved in the pathogenesis of Type 1 diabetes." Since there are currently 65,000 new cases of Type 1 diabetes worldwide, and that figure is growing by 3% to 5% every year, this association is more than troubling – it's a suggestion that diabetes (generally considered a non-infectious disease) may be spread by the flu (which is definitely infectious).
The flu-heart attack connection
If diabetes weren't enough to worry about as a byproduct of the flu, in research published in the Canadian Journal of Cardiology, researchers at the University of Toronto have demonstrated that heart attacks may be linked to the flu. They have long known that the number of heart attacks surges after a widespread flu epidemic, but their research demonstrated this association of the flu with heart attack in individual patients.
More important, their research indicated that patients who had received the influenza vaccine were less than half as likely to suffer from a heart attack or stroke during the following year. They concluded that vaccination against the flu may in itself constitute a powerful preventive therapy against adverse cardiovascular events.
So, although none of this research can be considered definitive until it has been replicated by many other researchers, its findings do lend some weight to the arguments for getting a flu vaccination. It is beginning to look like the impact of getting the flu is much more serious than the symptoms described at the beginning of this article. As unpleasant as those symptoms are, there are now indications that for many people getting the flu may increase their risk of contracting diabetes or cardiovascular disease. With this in mind, although I have never gotten a flu shot (because I rarely get the flu), I'm thinking of changing my mind this winter season. Fever and cold-like symptoms are one thing; increased risk of diabetes and heart attack are quite another.