With this article, we are starting out on a series about viruses.
We all know something about them. Have you ever had a cold? Of course! How about chicken pox? Warts? Hepatitis?
If you’ve had any of these (and many, many more), then you have come up against one of our smallest, and the strongest, of our disease enemies—the viruses.
The word “virus” comes from Latin, and it means slimy liquid, stenchy, poison. And that is strange because viruses don’t have any of these characteristics at all.
But that’s what the first virus scientists called them—and the name stuck.
Well, let’s start with their size. How big are they? They run from about 20 millimicrons to around 200. For most of you, the next question will be “How big is a millimicron?”
They are pretty small—about 25 million of them would equal an inch (or about 10 million per centimetre). Now that is really small, which is why we knew almost nothing about them for years.
Quite a few years ago, when I was going to university, we knew there were such things, but that’s about all. We thought that sometimes they just behaved like chemicals, and other times like living things.
The only virus I ever heard about at that time was the Tobacco Mosaic Virus.
We couldn’t see viruses because there was no way of making an image of them big enough to see. The optical microscopes only could magnify up to about 1,500 times or so—even the best university ones.
But in the 1940s, a new development appeared: the electron microscope. This could give you an image many thousands of times larger than the real thing. So now we can see all kinds of things that we never saw before—or even knew existed.
So, what do they look like?
There are two major parts to a virus. The “head” part consists of DNA material, in a container, inside a coating of protein—about as simple a living thing as you can get. Then it has a “tail” part which sticks out, and may have spikes coming out of it.
The “head” can be of many shapes: spherical, oblong, hexagonal, and icosahedron (which has 20 triangular facets). Some look like lunar landing modules and some like the ancient maces, with spikes sticking out in every direction.
Viruses are, as far as we know, the simplest form of life. They cannot reproduce, they don’t make any kind of food for themselves like green plants do, and they don’t have normal structures of life that even the simple things do.
So viruses are totally parasitic. They depend on other forms of life for reproduction and any other life functions.
How did we find them? That is another one of those great scientific discoveries which came about almost by accident.
During World War I, a French scientist and a British one independently noticed something funny about their bacterial cultures. There was a clear spot where no bacteria were growing.
Why? It seemed that an invisible parasite was attacking and killing the bacteria. We now know that’s exactly what was happening. An extremely small living thing was killing the bacteria.
These things—viruses—were so small that they could pass through all filters, even the Porcelain ones which could strain out anything we knew at that time.
And so the source of some of our most common—and some of our most awful—diseases was discovered. We can thank the election microscope and many dedicated scientists for that.
More on viruses in my next column.