As I mentioned earlier, I’ve been fascinated by the flu since about 1997, when they first discovered the Asian bird flu. The more I learned about the flu, the more fascinated I became. The Great Influenza of 1918 killed more people than died in battle WWI, WWII, the Korean War, or the Vietnam war: 20 to 100 million people world wide (exact numbers are not known due to the nature of the world in 1918, and the number of populations that were decimated by the flu.

So to start off, what is the flu?

The flu is a virus. There is some debate as to whether viruses are living creatures or not, but the important thing to remember about viruses is that they cannot be killed by antibiotics, and the best way to stop the spread of a virus is through inoculation through a vaccine. (Why hasn’t the government put out a flu vaccine? Because it takes about six months to create the flu vaccines that are given to the general population every fall.)

The debate about viruses stems from the fact that they cannot replicate on their own. If you want more viruses, the virus has to invade another cell, take over that cell, and force that cell to do nothing but make more RNA that makes more viruses. Then like the bad guy in a really bad action movie, the virus “blows up” the cell, releasing more viruses, which then continue the cycle.

A flu virus has two important proteins: hemagglutinin (H) and neuraminidase (N). The hemagglutinin protein allows the virus to invade cells. The neuraminidase protein causes the cell to burst after it’s done the virus’ dirty work of creating more viruses.

But that’s not what makes these two proteins so important–what makes them important is that they stick out from the surface of the virus–this means the white blood cells (the body’s defense system) have a chance of recognizing the virus and destroying it before it can kill the host.

Flu strains are named by those proteins. So when scientists talk about the flu, they’ll talk about the H3N2 strain, the H5N1 strain (the Asian bird flu), or in the case of the current virus, the H1N1 strain.

For the curious, H1N1 is the same strain of flu that went through the world in 1918.

So what does all this mean?

As I said previously, the body (and scientists) recognize flu strains by their H and N proteins. When a stain of flu infects your body, if you are healthy, and if your white blood cells recognize that strain of flu (either as a previous invader or because you were immunized) then your body can resist the infection. If you are unhealthy, or if the strain is one that your body cannot recognize, then you get sick. And you remain sick until your body can recognize the invader and fight it off.

Now if we’ve only discovered a handful of flu strains, then why does the flu come around every year, and why do you get sick more than once with the flu?

This is because there are two types of changes the flu virus makes: drift and shift. Just like everything else in the world, viruses are constantly mutating. A small mutation is called a drift. In drift, there is a small change in either the H or the N proteins. This drift means that you can get the flu every year if you’re unlucky. However, your body is able to fight of the infection relatively quickly, because the mutation is small, and thus similar to earlier versions of the flu.

Shift is a big mutation in the virus. It changes the proteins significantly so that they cannot be recognized by the body. When this happens, the virus becomes deadly, because the body essentially cannot recognize the virus as a familiar invader.

The thing to remember is not to panic and freak out. First and foremost, wash your hands. Thirty seconds with regular soap is what you need to clean your hands. No anti-bacterial soaps, no hand sanitizer. If you’re around someone coughing and sneezing back away quickly and wash your hands. And if YOU feel unwell, do NOT go to work. Do NOT go to school. Do NOT go shopping. Rest and fluids and get to the doctor as soon as you can.

If you have any questions, please ask. I’ll do my best to translate science into plain English.

Recommended reading:
Flu, by Gina Kolata
The Coming Plague by Laurie Garrett
The Great Influenza by John Barry
The CDC’s flu website

(Of the three books, Gina Kolata’s book is probably the most accessible. It’s my personal favorite anyway.)