Swine flu

As an immunologist and a Mom, I feel I should probably chime in on the swine flu. I'm not an epidemiologist, or a psychic, and I have no idea if this is going to turn into a deadly global pandemic. I certainly hope not, and I do have fears for the Spawn, but although the media coverage has actually been pretty detailed (and fair in my opinion) I'm going to discuss this in layman's terms for those interested.

What is the swine flu?
Every year, I, at least, get my flu shot. What is the flu shot exactly, and why do we need to get it every year?

The flu virus is actually very simple. It has a protein coat with RNA inside it. Imagine a balloon filled with pieces of spaghetti. When the virus infects a cell, human or pig or bird or whatever, the RNA (spaghetti) is injected into the cell and the protein coat (balloon) is left outside. In case everyone doesn't remember the Dogma of molecular biology from their basic high school biology class DNA->RNA->protein. Flu viruses don't have DNA, so they coopt the machinery from the infected cell to make protein - a bunch of new protein coats in fact. They also replicate their RNA. Now the infected cell has a bunch of RNA (spaghetti) and protein coats (balloons) floating around in it, the virus assembles (the spaghetti goes into the balloons), and the new viruses (many many MANY more) go on to infect other cells.

Back to the flu shot. Your immune system produces antibodies to different proteins on the viruses protein coat, which neutralizes the virus. You get the vaccine because the immune system is much faster the second time it sees a virus than the first, and the dead (or live but weak) vaccine that you get is enough to stimulate the immune system without making you sick. The problem with the flu is 1) it mutates very quickly and 2) there are a bunch of strains out there. If you've heard about H1N1, H5N1, etc, the H and the N are different proteins in the protein coat of the virus. They are what the immune system makes antibodies to. Every year, vaccine makers try to predict what will be the most prevalent strains of the flu and make the vaccine to those strains. They're usually pretty good (which is why I get the flu shot).

Back to the swine flu. Sometimes (and it's not so rare) two or more different types of flu viruses infect the same cell. So instead of only having 1 type of spaghetti and balloons in a cell, you get more than one. You can imagine with a big mixture of, say, red and blue spaghetti that when the spaghetti is going into the balloons, sometimes it gets mixed up. If you have a blue balloon with mostly blue spaghetti and 1 strand of red spaghetti you have an entirely new virus. This happens all the time among human viruses, which is another reason you need to get your flu shot every year.

Much more rarely, because it is difficult for a virus specific to humans to get into a pig cell (or a bird cell), pigs or birds can get human flu, or humans can get pig or bird flu. This usually happens in someone who spends a lot of time around pigs or birds. Pig or bird flu in humans tends to be very dangerous to people who get it because the proteins are so very different that the proteins of the human flu (which your immune system has seen for a long time). Usually, though, it doesn't spread from person to person because it's only really made to infect pig or bird cells.

The problem comes in if both a pig and a human (or bird) virus infect the same cell at the same time. If the new virus that comes out happens to have some proteins to spread from human to human and other proteins specific to pig, it can be very dangerous. That is what the current swine flu is (and I read that it also has bird RNA in it).

Why are we afraid?
In 1918, there was (we think) a similar virus that spread across the planet. The pandemic wasn't taken care of properly. We were at war so countries weren't exactly forthcoming with knowledge sharing; medical personal were either in the trenches or overworked; there was no anti-viral tamiflu stock; secondary bacterial infections often set in after the flu left. It's estimated that 20-50 million people worldwide died. Scary stuff. Notably, the 1918 flu primarily killed healthy 20-45 year old people, not the very young and very old like it normally does. There are a number of theories about this, but no one really knows why. This new swine flu also seems to be killing healthy 20-45 year old people. A frightening parallel. Also, the 1918 flu was H1N1, as is the new swine flu. Of course, H1N1 flu has been in circulation since 1918, nearly every season, but the similarity has raised some people's concern.

Reasons this probably won't be 1918 all over again.
A lot of things are different now than in 1918. Medicine has dramatically improved, as, perhaps more importantly, has epidemiology. I would like to think, despite my fascination with infection in general, that we can handle this. It is definitely not clear at this point how deadly this new swine flu is. The large number of deaths in Mexico could be from substandard care. A lot of people don't have access even to running water. We don't know how deadly 1918 was - they didn't have genetic screening to tell us home many people got low level infections and SURVIVED. Hopefully it's just a slightly more severe case of the normal seasonal flu.

What am I going to do?
I'm going to watch and wait. The problem with the flu is its high rate of mutation. It could easily mutate into something a lot more nasty, especially as it spreads. The timeline of the 1918 epidemic was over a year, not a month, and there was a lull where the virus appeared to be gone. We can't give up vigilence too early. Hopefully a vaccine will be developed (although I read this flu is slow-growing, not a good sign) and ready for distribution by October. Hopefully this is all sensationalist media response. But definitely wash your hands - well and often. Cover your mouth when you cough or sneeze. Standard prevention.

Anyway, I hope that was informative and that my whole spaghetti/balloon metaphor wasn't too stupid (I seem to be missing the creativity for a better one right now). I would be glad to answer any questions, or go into more details if anyone is interested.