Our bodies have marvelous defenses, a complex system
commonly referred to as the immune system
. This sophisticated system comes into play when our bodies are "invaded" by a virus. This action causes our bodies to produce an "immune response," to fight off the unwanted invader.
But let's look at the invaders for a moment. Viruses are sneaky little bugs. They enter our body via droplets from a cough or sneeze, or even from our hands and fingers, where we have touched a surface or skin the virus has landed on, and then transfer it to our mouth or eyes.
Once the virus enters our bodies, our internal body temperature makes it a perfect place to use as an incubator, making multiplication easy. The virus particles seek out special blood cells called "B-Lymphocytes," entering them and redirecting them to produce more viruses.
Normally, when attacked by a virus, our bodies recognize the foreign invaders from the normal cells making up our immune system, and launch an immune response. White blood cells called macrophages attack and engulf the invading virus particles, killing them. Our bodies make about one million of these cells everyday in our bone marrow.
But sometimes, when an invading virus gets the best of us, our body will send out special cells called lymphocytes. We have two kinds of lymphocyte
s, T and B cells. Most of us have heard of T-cells. T-cells are needed to kill off other cells in our body that have become infected with germs.
Without T-cells, the other antibody producing lymphocytes called B-cells couldn't work properly. B-cells bind to a virus, stopping it from replicating. But they also are designed to go a step further. They "tag" the virus so that other white cells, the macrophages, can kill it.
Once the virus has been overcome and cleared from our bodies, some of the B-and T-cells hang around, remembering the viral code, so that next time the same virus tries to invade, our immune system will be able to identify if faster and get rid of it.
This is called "acquired immunity." As an example, once we get the mumps, we develop an acquired immunity to them. This immune response is what helps scientists to create vaccines, using weakened strains of the viruses to create an immune response in our bodies, giving us an immunity to a particular virus.
The flu virus is much more complex and more difficult for our bodies to protect us against. This is because it is able to mutate quickly
, and it can pass from humans to avians to swine and then back to humans, sometimes with apparent ease. This changing to different hosts and back makes them almost unrecognizable to our immune systems.
In recent studies of the flu virus, it has been found that after the virus enters the "B-cells," it disables and eventually kills the cell's antibody production mechanism, breaking down the body's first line of defense. This kind of attack by the flu virus makes it take much longer for the body to regain its defenses and fight off the virus.