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A Flu or Two!

© Debbie St. Germain

How many of you have had the flu? How many times have you gotten the flu a second time and said "I've already had the flu, how can I get it again?" Today we will learn why we can get the flu more than once; but, first, let's talk a little about the flu and its history.

Influenza, also known as the flu, is one of the oldest and most common diseases known to man. Hippocrates was the first scientist to mention flu in 412 BC. The influenza virus is so small it can only be seen with an electron microscope -- it is only 80 to 120 billionths of a meter in diameter! If you looked under a microscope, the virus would look like a tiny spiked ball. Because of its microscopic size, the influenza virus can be picked up by you without your ever knowing it.

The spread of the influenza virus is by airborne droplets (sneezing or coughing) or by contact with an infected person or contaminated items, like bathroom sinks. When a person sneezes, the droplets can spread up to 150 feet a second. When the moisture from the droplets evaporates, it leaves behind thousands of influenza germs. These germs may be inhaled as they float through the air or be picked up on your hands from contaminated surfaces.

So, how can you get the flu twice? Doesn't your body build up immunity? When you get the flu, your body builds up antibodies (proteins that fight disease in your body) that respond to that particular virus. The next time you get the same flu, your body would recognize the virus and produce antibodies to fight off the flu. The problem is, these antibodies will not protect you if the influenza virus has changed its structure. Viruses can change their structure during the replicating process. That is when the influenza uses its own RNA (an acid in a living cell that carries the codes for genetic information) to make new RNA messengers that will instruct the infected cell to make more viral proteins.

When the virus makes the new RNA, it makes an exact copy of itself, like a mirror image. Influenza virus does not have a system to notice or correct for errors during this process. These errors can make changes to the new virus that are different enough that your immune system cannot recognize it. If the immune system does not recognize it, it will not be able to produce antibodies against this new virus. Without antibodies, the virus can go about its business of infecting your cells. This process is called antigenic drift, a gradual evolution of the virus or small mutations that change the proteins in the virus. These changes can cause epidemics of flu.