“The Problem Child of the Seasonal Flu”: Review by Paul S.

“The Problem Child of the Seasonal Flu”: Review by Paul S.

           As I am currently a healthcare worker in a primary care setting, I have so far seen dozens of patients who have the flu this season, and one that was so sick we had them life flighted to the hospital where he was in the Medical ICU for a week. As I was reviewing possible articles, this one caught my eye with its title, “The Problem Child of Seasonal Flu”: Beware This Winter’s Virus.

                                                               I had already been curious about why this years flu season has been so severe, and reading this article helped explain it for me.  It starts by saying that the H3N2 virus strain that is out and about this winter is deadlier than many of the other influenza virus strains, partially because it is especially hard on the health of seniors. The article states that the reason for that isn’t yet fully established, but they have a theory that peoples immune system “imprints” onto the first strain of flu virus that they come into contact with in their lifetime, making them more resistant to that particular strain but less resistant to other strains, even after being vaccinated; The concept is formally known as 'original antigenic sin'.

                                                               Based on that theory, it makes sense that more seniors will be hospitalized or even die from the flu virus on years that the H3N2 virus is active, since it was not around during their childhood. But beyond that theory there are multiple other factor contributing to the H3N2 virus being so deadly. One factor is that people over the age of 50 have weaker immune systems to begin with. Another is that it does not grow as well as other virus strains in eggs. This is a problem because our flu vaccines are currently grown in a egg based medium, and when the virus is being incubated for the vaccine, the H3N2 virus tends to mutate slightly, so even though you get the vaccine designed for that strain, the immune system has been exposed by the vaccine to a slightly different strain, and therefore doesn’t have the correct antibody match. Because of this, the H3N2 component of the vaccine is less than half as effective as the other viral strain components. “We don’t have a flu vaccine problem so much as we have an H3N2 vaccine problem,” Belongia said.

                                                               What else makes the strain of the virus so troublesome? Well, three other factors were mentioned in the article. The first is that traditionally the influenza virus will bind to blood cells, and that is how it is usually found for testing in the laboratory. Unfortunately, the H3N2 strain will not bind to blood cells, and while there are other tests they can perform, they are more time consuming, so not as much testing gets done on it as the other strains to identify if the vaccine needs to be updated. Secondly, the virus mutates faster than the other strains on its own, independent of the egg vaccine mutations. Because of this, and the original antigenic sin concept, it is becoming a problem for more and more people every year with new mutations. Thirdly, the virus strain is very tenacious. Traditionally, only one strain of influenza would circulate at a time, and when a new strain came to circulate, it would push out the old strain. However, when H3N2 came around, it stayed, even after other viruses started circulating. Thanks to this we can get sick with influenza multiple times in a single season, between influenza H1N1, H3N2, and the B strains.

                                                               The paper concludes by pointing out that the most problematic thing about the H3N2 virus strain, as well as the hardest to combat, is the fact that while it causes the most severe illnesses it is also the strain the vaccine is least effective against. Unfortunately for all of us, I believe based on this article we might expect this years flu season to continue to worsen unless scientists discover a way to more effectively test the H3N2 virus and make a more effective vaccine. As a healthcare worker I still strongly recommend everyone get a flu vaccine each year, as the benefits still outweigh the risks, even with the declining efficacy. I found this article especially interesting since this years flu season has been worse than many recent years, even though it has yet to run its course.

By Helen Branswell, STAT on January 9, 2018

https://www.scientificamerican.com/article/ldquo-the-problem-child-of-seasonal-flu-rdquo-beware-this-winter-rsquo-s-virus/