Influenza (a.k.a. “the flu”) — it’s a topic none of us ever tire of, not only because it’s so widespread (five percent to 20% of the U.S. population gets it every year), but also because of the recent ominous predictions of a coming pandemic as well. The latest development may prove to be quite important, as it could mean that certain people are prone to severe forms of the flu because of their genetic makeup.
Doctors and laypeople alike have long wondered why some of us have mild reactions to this virus-borne respiratory illness and others have more severe reactions, sometimes even leading to death. During the infamous 1918 flu pandemic, for example, it was often seemingly healthy young adults who succumbed to the illness.
The rise of avian flu, or “bird flu,” is something that has prompted the concerns of another potential pandemic. This type of virus can be found in the intestines of many types of wild fowl, although the birds themselves don’t get sick from it. However, they can carry and transmit the virus around the world, infecting domesticated birds that do actually become ill.
This virulent type of flu has been found to jump from birds to humans, although the Centers for Disease Control and Prevention (CDC) says that this is rare. However, avian flu is similar to the 1918 flu, as, according to the CDC, it has been shown to have lethal consequences in otherwise healthy individuals, while others seem to fight it off in the normal fashion.
But why is this? Wouldn’t you think that a healthy person should be better equipped to battle the effects of viruses? In fact, it seems that in certain individuals, it is their immune system response that’s lethal — their bodies go into overdrive to get rid of the virus, which leads to lung inflammation and the overproduction of fluid. The reason why this happens hasn’t been fully understood or proven, until recently.
In a recent study done at the Southern Illinois University School of Medicine, researchers decided to compare two different kinds of mice: “Type B” mice and “Type C” mice. Past studies have demonstrated that Type B mice were at higher risk from death from the flu (50%) than Type C mice (10%). The Southern Illinois University researchers wanted to take a closer look at this connection.
They infected both groups of mice with a form of avian flu. Thirty hours later, the researchers checked for cytokine levels — cytokines are the proteins that are part of the immune response and are instrumental in causing inflammation. They found that cytokine levels were much higher in the Type B rodents. Nevertheless, the amount of the virus found in the lungs of both groups of mice was the same.
A follow-up study looked a little closer and found that flu- infected Type B mice had greater levels of “immune- related messenger ribonucleic acid” (mRNA) than the flu- free mice did. In fact, the levels in the former were an average of 24 times higher. In Type C mice, the infected rodents had only thrice the levels of mRNA than the uninfected ones did. Note that mRNA is a genetic template for protein synthesis.
Together, these two studies basically mean that there is a genetic component that seems to determine how an animal (or human) reacts to the flu. The next stage in the process is to figure out what specific human genes play a role in determining this. We’ll let you know if we hear anything on this front.
All of this talk about genetics and the flu is important for several reasons: 1) if doctors can determine that you are genetically prone to experiencing serious flu complications, then they can take stronger measures to prevent it (i.e. you will be at the top of the list for the flu vaccine) and to monitor you more closely; 2) it targets inflammation as an important aspect of severe flu that needs to be treated; 3) it brings up the controversial topic of a genetic-engineering solution to influenza, which is becoming increasingly resistant to modern medicine. Until we hear more, talk to your doctor about the flu shot.