There are many common viruses that we get exposed to on a regular basis, but the one virus that causes the most trouble year after year is the influenza virus. It is so common and damaging that we give it the respect of naming a season after it. Every pediatrician every winter experiences what we simply call “The Flu Season.” We can feel it when the influenza virus rears its ugly head because the entire medical community, from offices to emergency rooms, swells with sick visits. This article will help you understand more about how the influenza infection came to be and the options for prevention.
At some point in human history there was an ambitious flu virus that was causing its usual trouble infecting a bird. But this virus had bigger aspirations. This virus set its sight on infecting a human. Other flu viruses had tried to take hold of humans before but none had been able to sustain a contagious human infection. This one was different. The virus waited for the bird to sneeze, and then it spread by inhalation of a large, airborne particle to a nearby human. Once inhaled, the virus found one of the cells in our respiratory tract. It had previously altered its genes just enough so that it could evade our immune system and replicate by hijacking our own cell infrastructure. It made millions of viral children. These new viral progeny were released, leaving our cell weakened, and, once released, each new virus found another cell and another cell and another cell, and so began the grand human battle against influenza. As we overcome this virus we generate fever, cough, sneeze, sweating, vomiting, aches and fatigue. Certain individuals are known to be at higher risk for more serious effects from an influenza infection. These are the youngest, the oldest, those with respiratory problems and those individuals with weak immune systems. Even if you are not one of those high-risk people, the flu will make you feel awful for many, many days.
You have all heard the stats: each year, 500,000 people worldwide die from influenza, approximately 25,000 Americans die and millions of people suffer. Thankfully, on an individual level, we almost always win the battle against influenza by responding with the full weight of our immune system, and then we retain the memory to fight off this virus…unless it changes and tricks us. During influenza infections, small genetic adaptations are acquired by the virus. The changes that most successfully cloak it from our immune system become the predominant strain for any season—Darwinism on the smallest scale. Year to year these genetic adaptations are small but often enough to keep us susceptible even if we have had influenza in the past. This is the reason that scientists have to change the flu vaccine each year—they are taking their best educated guess as to what the flu will look like, and targeting the seasonal vaccine with that prediction in mind. Most of the time they get it right or are very close, and the vaccine effectively primes our immune system for the seasonal strain. Those who get vaccinated are clearly better off than those who do not. Every few decades, however, a human flu virus goes back to its roots and infects other animals, like a bird or pig. Within these other animals it dramatically reorganizes and then jumps back to us with its new genetic material and a new subtype is born. You all remember the swine flu? That was one of those seismic influenza shifts.
Someday we will create a vaccine that can generate prolonged immunity to all strains of the flu, but we are not there yet. We thought we were close when the live-attenuated influenza vaccine (Flumist) was created. For many years, this form of flu vaccine was able to generate longer immunity and showed effectiveness against strains of influenza not included in the vaccine. Through surveillance, something happened after the H1N1 strain (swine flu) component was introduced and we found the Flumist is not working anymore. It is unclear why this happened, and it once again highlights the challenges we face against an ever-changing dangerous foe. So for now we go back to the seasonal flu shot.
We often hear people ask, “My kids don’t get sick or they are not high risk, so why get the flu shot?” A good analogy for influenza vaccination is comparing it to wearing a seat belt. You drive around in your car every day, following traffic rules, but every time you get in that car there is a small risk of getting into an accident. You exponentially improve your chances of walking away unharmed or surviving a crash if you wear a seat belt. Seat belts aren’t sci-fi force fields that can protect you from all injuries. As it relates to the flu season, you walk around every day responsibly washing your hands and avoiding friends/family who are very ill, but every winter there is a chance you will be exposed to the flu. Getting vaccinated greatly improves your chances of staying healthy or having a mild case of the flu. Vaccinations are not sci-fi germ nets that block every exposure.
As you head into this flu season, hopefully you have a better understanding of the human relationship with the influenza virus and the challenges we have faced. It is a fascinating and sometimes terrifying relationship, but with better understanding and common sense we can win this battle together.
Dr. Darren Saks is a pediatrician at Tenafly Pediatrics.
