How do viruses make us sick?

Well, it’s not only us that get sick. Thousands of other animals, birds, plants, insects, and even bacteria, get sick, too.
In the first place, a virus can’t do anything to harm anything unless it is inside a cell. As long as it is outside of a cell, on any surface, floating in the air, in the water, on your kitchen counter, or your own skin, or inside your intestine, it can’t do you any harm.
Every cell has little “receptors” on the outside of itself. Some of these are called “docking” areas. The virus finds one of these, into which part of its outer covering can fit (like a key in a lock).
This enables it to go right into the cell.
In the process, its outer covering is lost. Now the genetic material of the virus is floating in the cell.
The virus can convert that material into dioxyribonucleic acid. This DNA goes into the nucleus of the cell and takes over. And it can reproduce.
Finally, the cell is overwhelmed by this new DNA and it dies. But before it dies, it releases a whole host of new viruses to attack other cells. And so it goes, on and on.
As long as there are more viruses, and more cells to get into, this action goes on.
How do we know all this happens? Once more, we can thank the electron microscope, which enables us to actually watch some of these things as they happen.
So the virus continues happily on its way, making more DNA, making more viruses, and pushing them out through the walls of living calls. In this process, the “host” cells can get very sick or die.
Some viruses are the so-called “quiet” ones. These may live in mosquitoes, birds, or other living things for years, not doing them any harm at all. But they can do great harm when they get into humans.
And some can live in humans for years, too, and do no harm. Then they “flare up” and make a person sick.
And some may cause cancer changes in cells. These may be triggered by chemicals, irradiation, other viruses, or simply because the person gets old.
Viruses are all around us—in uncountable numbers. So are a lot of other things (bacteria, pollen, spores from lower plants, many kinds of microscopic animals, and so on).
Most of the time, these things don’t hurt us at all. Only once in a while, some change takes place—and the tiny things can affect us.
In a cubic centimetre of soil (about the size of a sugar cube), there may be hundreds and hundreds of living things—most of them too small for us to see. Among these things are certainly viruses.
Viruses are new to us because we only have known about them for less than 100 years. But they have been with us for a very long time. You may have heard about the great influenza epidemic of 1918, in which about 20 million people died.
We know from the pustules on the face of Ramses V that viruses killed the pharaoh nearly 3,000 years ago. Yellow fever and smallpox have been great scourges over the centuries.
We have our modern plagues, such as the dreaded polio not that long ago and now AIDS.
Many viruses change in the course of time. Take the influenza virus, for example. There are several ’flu viruses, and some of them seem to change each year.
So, every year, scientists have to come up with their “best estimate” as to what type of ’flu is going to go around. That’s why the ’flu shot is different every year.
They have done extremely well in their “intelligent guessing” for many years now.
And how are we protected against these tiny, fierce enemies? That’s for my next column.

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