Saturday, May 2, 2009

What's the Deal with Swine Flu?

By now, everyone has heard that the swine flu is slowly spreading around the world. The World Health Organization (WHO) has raised the pandemic threat level to 5, which means that an outbreak is imminent; a threat level of 6 means an outbreak is occurring. To me, the word "outbreak" makes the swine flu sound more ominous. Maybe it's because I only expect to hear about an outbreak of this scale in a Hollywood movie.

In this post, I'll try to give you the basics of the flu and explain why a swine flu is now infecting humans. The information below was gathered from reliable health sources, such as the WHO and CDC.

What's in a name?
Influenza, the flu, is believed to have been around for a few thousand years. The ancient Greek doctor Hippocrates, who is considered to be the father of modern medicine, has described the symptoms of the flu in 412 B.C. but it didn't have a name.

Fast forward to the 1700s–most people believed that astrological or occult occurrences caused health outbreaks and so an old Italian word
influenza, which roughly meant influence of the stars, was given during an outbreak in Italy and the name stuck.

The flu virus
The flu is spread by a virus, which is very different from a bacteria. A bacteria has the machinery of life, which allows it to copy its own DNA, make energy, and reproduce. A virus does not have this machinery; instead it relies on a host cell to do all the hard work for it.

Viruses come in many shapes and sized, but most have a few common features, such as a protein shell on the outside and precious DNA (or RNA) blueprints on the inside. Below is a cartoon of a flu virus I found on the web. The blue and green spikes are the proteins and the genetic blueprints are on the inside.

The flu virus has many proteins, but two key proteins are haemaggluttinin and neuraminidiase, and are abbreviated H and N, respectively. Haemagglutinin allows the flu virus to enter a cell and neuraminidase allows the virus to exit the cell.

By the way, flu viruses are named by their H and N proteins. The flu goes by names like H1N1 (swine flu) and H3N2, etc.

How it works
The flu virus uses the H protein to enter cells in the back of the throat and in the lungs. Once inside, the virus falls apart and the blueprints eventually find their way to the cell's machinery which contain instructions to make more viruses; eventually the cell becomes full of newly made flu viruses. When the time is right, the viruses use their N proteins to escape and spread to other cells, and eventually to other people.

Here's a cartoon of the flu virus "life cycle" I found on the web.

How do humans get the swine flu?

All sorts of animals get the flu. Most flu viruses that infect animals are specific to the species. This means that a flu virus that infects dogs have H and N proteins that can only enter dog cells.

Interestingly, some flu viruses that infect humans can also infect birds and pigs! These viruses have H and N proteins that allow the entry and escape process to occur without a hitch.

Pigs are considered mixing vessels since they can be infected by human and swine flu viruses. Why mixing vessels?

Imagine this, if a pig is simultaneously infected with two different flu viruses (swine and human), there is a chance that the viruses can infect the same cell. As the viruses use the cells machinery to assemble copies of themselves, there is a chance that mixing can occur, that is some of the proteins and blue prints from the human virus can mix with the proteins and blueprints from the swine virus. In the end, a new flu strain can be created that is different from the original human strain and can cause new cases of the flu.

Below is a cartoon from the National Institute of Allergy and Infectious Diseases that shows how new flu strains form.

Bird flu worries
Not too long ago, health scientists were worried about an avian flu (bird flu) called H5N1. Many deaths were reported in Pacific Asian countries but no pandemic alert was raised.

Doesn't the flu vaccine help?
Even if you get a yearly flu vaccination, you are not immune to the new H1N1 swine flu strain. Unfortunately, the flu virus undergoes subtle changes each year. This means that an H1N1 strain from this year could be different from the H1N1 strain next year. This is why it is always important to get a yearly flu vaccination.

In the end, your best bet is to use common sense and wash your hands regularly. If you are sick, stay at home and get plenty of rest.

Please visit the following websites for more information:

WHO Influenza Page
CDC Influenza Page
National Institute of Allergy and Infectious Diseases Influenza Page

Dr. Dave

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