By Arshya Gurbani
I’m sorry about the title, too. I heard a pretty ridiculous pun today, and I guess they’re just contagious…much like the flu.
That’s right–sure as the sun rising each morning and the certain as the pride every Tarheel felt following last week’s momentous basketball victory…flu season is back again. In the US, flu season tends to peak somewhere between December and March. A highly variable virus, influenza strains are often different than the previous years’, which leads to the need to constantly update and refine recommended vaccines for the year. It’s why you have to go back to get a flu shot every year.
Of course, it’s important to know what you can do to prevent getting ill. If you need a refresher, quick shout-out to a fellow UpstreamDownstream blogger from the past: Surviving Flu Season. But I thought it’d be kind of fun to talk about the influenza virus itself. (You may roll your eyes at “fun” but you’re still reading…)
There are 4 types of the influenza virus, A-D. Influenza A and B are the most common causes of the seasonal epidemic known as the flu that afflicts the US. The A viruses has hemagglutinin and neuramidase surface proteins, also called H and N subunits. That’s where the name of a particular strain comes from. Remember the H1N1 pandemic in 2009? That’s right–the H1 refers to 1 of 18 known H subtypes, and N1 refers to one of 11 known N subtypes. Both of these proteins live on the outside layer of the virus, also known as the viral envelope. They act sort of like bridges, connecting the virus to our cell membranes by latching on to one of the sugars in our cell membranes, sialic acid–H helps the virus enter our cell, and N helps it leave. Pretty nifty, right? Here’s a helpful visual from David Goodsell’s “Molecule of the Month” blog featuring H and N:
As mentioned earlier, the strain of influenza virus most prevalent in any given season can change. Now that we have a vague idea of the naming system, let’s talk about which strains vaccines recommended for the 2016-2017 season protect against. There are 3-component and 4-component vaccines:
- A/California/7/2009 (H1N1)pdm09-like virus
- A/Hong Kong/4801/2014 (H3N2)-like virus
- B/Brisbane/60/2008-like virus (B/Victoria lineage)
- B virus called B/Phuket/3073/2013-like virus (B/Yamagata lineage) –only in 4 component vaccines
So far this season, according to a Morbidity and Mortality report looking at data from Oct-Feb, the A(H3N2) virus has been the most prevalent. Around 94% of infections were caused by Influenza A, and 98% of these were attributed to the H3N2 strain. Overall, the report says, it’s been a pretty moderate season.
I hope you enjoyed that brief dip into biology–who knows, if enough of you did, maybe this post can go, you know ….viral.