Epidemic!

WARNING: The United States is in the midst of an epidemic! This outbreak has been cited as the cause of more than 9% of deaths during the first week of the new year. Nearly all fifty states have reported widespread infection and hospitalization rates have spiked. But in the words of CDC Influenza Division Director Dr. Dan Jernigan, “yes, [we’re] definitely in an epidemic, but that happens every year in the United States and in the Northern Hemisphere with influenza.” 

Yes, that’s right. This epidemic that America is struggling with just so happens to be the same one we that face year after year: the flu. 

Yet again, we come to the question: how is something no more than 120 nanometers across able to wreak so much havoc? Our culprit is another small RNA virus: influenza! 

Image courtesy of Kat Masback.

But influenza is certainly not the shrimpiest kid on the block.  Instead of having just a single gene like a rhinovirus, it has upgraded to a whopping 10 genes, and it has a bonus feature: an envelope! Much like the plasma membrane of our own cells, a viral envelope resembles a bubble of fatty molecules and serves as another defense for the virus. 

The influenza envelope has two surface proteins embedded into it. Known as H and N or hemagglutinin and neuraminidase respectively, these proteins play crucial roles in helping the virus grab onto cells in our airways and in defining our immune response. In fact, they are so important that we name strains or forms of influenza according to them! 

For example, the strain we have seen this winter is H3N2, aka. a form of the influenza virus with the third type of H and the second form of N. 

But more broadly, the classification of the human influenza virus is as simple as A, B, C! Influenza A is broken down into the H and N subtypes we discussed above, and it, along with its accomplice Influenza B, causes the seasonal outbreaks we look forward to each and every winter. 

But it seems that after more than 50 years of fighting this virus, we should have figured it out by now! 

But, influenza A and B are fickle and indecisive, making it difficult for us to pinpoint them. These viruses just can’t stand still, continuously shifting via a process called antigenic drift. 

Antigenic drift is a gradual change where small mistakes in copying the viral genes cause minuscule tweaks in the identity of the new virus particles produced. These mutations might not make immediate drastic transformation, but with time, they stack up. 

Antigenic shift is the big brother to antigenic drift and the big bad behind the Swine Flu (H1N1) panic and pandemic of 2009. Remember way back to elementary school when H1N1 came from nowhere? All of the sudden, everyone had to get a swine flu shot, and school halls were riddled with rumors about how swine flu killed people! A titanic change had occurred in the flu virus, creating entirely new types of H and N that we had never seen before. Antigenic shift may be rare, but it is undoubtedly terrifying! 

Either way, since influenza can’t seem to make up its mind about what surface proteins will be in style this winter, we just have to wager an educated guess about what to include in the annual vaccine. As a consequence, vaccines might not always be entirely effective. (This is not to say that you shouldn’t get the flu shot; rather it is an essential preventative measure required to stay healthy!) 

This flu season, in particular, is the most intense since the Swine Flu in 2009. But, why is the flu so severe this year? 

Image courtesy of Agência Brasília. 

The specific strain of influenza A that is widespread throughout North America right now is known as H3N2. And according to Live Science, H3 strains of influenza tend to cause more serious cases of the flu. Vaccines have also been shown to be only 30% effective against H3 strains of the virus, relative to the typical 50-60% efficacy against other forms of influenza. 

In other words, this year especially, you must be sure to get a flu shot – its not too late – and to see a doctor within 48-hours of seeing symptoms of the flu. Although flu symptoms do tend to resemble those of a cold, the flu comes on more suddenly and often involves a high fever (above 101°F). 

Taking precautions similar to those for avoiding the common cold (check out last week's post), can also help keep the flu away! As always, best of luck staying healthy.