To the layperson, disease names are generally meaningless, but in actuality they carry immense weight, and in many ways the key to understanding how and why pandemics of mutated flu viruses occur. Take for instance the H1N1 scare of 2009. Thanks to the ever-vigilant media, most people knew this was an outbreak of swine flu, but they didn’t know why the name “H1N1” was significant.
The “H” stands for Hemagglutinin and the “N” means Neuraminidase. Both are protein spikes that sit on the surface of a virus and allow it to attack cells. By changing the form of these proteins, the virus changes the tactics it uses as it enters a new host.
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Both of these protein spikes have a number of variations that dictates how they operate and what kind of host they are able to infect. Hemagglutinin (H) has 16 different strains ranging from H1 to – as you might guess – H16. Neuraminidase (N) has only 9 variations, but within each alphanumeric pairing are numerous other alterations that can take place which permits the virus to circumvent medication and jump from one species to another.
Every flu virus takes one of each of these protein spikes before they attack a system. These determine the way the virus is going to operate once it is introduced to its host. If an animal is infected with H1N1 by itself, then the system will only produce H1N1. It is generally unable to make any new strains. But usually a virus is not alone. If an animal or person gets both an H1N1 and H2N2, then the two viruses are going to begin sharing their genetic information and create viral progeny that is part of one and part of another. This is what geneticists refer to as “reassortment.”
It is this mutation that causes the flu viruses to be so troublesome. H1N1 can infect people and pigs and birds. H2N2 is a little more specific and won’t work on pigs. That is, until it meets H1N1 and the two begin reproducing using each other’s DNA. Now the virus is capable of jumping species; and once it gets into its new host, it starts to learn from whatever flu bug they may carry, say H4N9.
These jumps make the virus more dangerous because it has a whole new bag of hideous tricks to dig into, and the immunities of the newly infected organism have no defense. The immune system has never had to fight off an H2N2 virus that looks like an H1N1 virus but attacks like an H4N9. It’s like going into the civil war with an Apache helicopter. There is no way to combat it because the natural defenses have never seen anything like it before.
The 2009 H1N1 outbreak was an example of this process in action. Scientists hypothesized a scenario similar to this: Humans were carrying old H3N2 strains that were left over from the 1968 pandemic. These mixed with some H1 in swine and then found some N1 from an unknown source, along with a variety of unidentified pieces that were the result of multiple generations of reassortment. The final product was a heavily altered version of the H1N1 that found a home in pigs where it began to replicate. It had learned all sorts of deadly genetic tricks by that point and when it found its way into humans, the result was the flu panic.
Further Reading: Be sure to read BioNews Texas’ recent exclusive interview with Baylor flu expert Dr. Pedro Piedra, who finds the current bird flu outbreak “concerning,” and explains how the U.S. is“better prepared” compared to past flu pandemics.