Viruses! Every cold and flu season the word pops up as we, or those we know, get "the bug."
But what are viruses? And can they be good for us?
So grab your microscope and come take a peek in the world of the very small.
The survival of a species means it must meet two basic requirements.
It must take in nutrients from something else, often something that is alive.
It needs to reproduce, creating the next generation.
For plants, this is done by taking in the good stuff from the soil, water, air, and sunlight – then producing seeds.
Some animals get what they need from these plants.
Still others get what they need from the animals that eat the plants.
And others live by making do with the leftovers of other living things.
All this is even true in the world of the very small. Microscopic things called bacteria live in and on another living creature. Many of our diseases come from these tiny creatures.
Escherichia Coli, commonly called E. Coli. This image shows them greatly magnified from their original size of less than ten-thousandths of an inch.
But stranger things are to come.
Viruses take all this in a stripped-down, no-frills way. Why make things difficult when you can simply have other living things – cells really – do all the work for you?
Take the astrovirus.
Electron microscope view of Astroviruses by Graham Beards*
These viruses do nothing all day but float around, looking for a target cell. Then it goes into Trojan horse mode.
and hop into action.
First, a virus attaches itself to the target cell.
Like a doctor giving a shot, the virus shoots its DNA into the cell.
The virus DNA gets mixed in with that of the target cell.
The victim cell dutifully follows its new instructions, now making new viruses.
Once the cell gets too crowded with viruses, it burst open – spilling multiple viruses into the outside world.
It's a simple life – if you can call it that. Some consider viruses a form of life, and others not.
The problem is that the viruses doing their thing means destroying healthy cells – leaving sickness as it goes.
Meet the gang
There is a virus for any living thing you can imagine – plant and animal. Here are a couple of types that go after humans:
But perhaps the most common human virus is the common cold. But the cold is not one virus, but a whole family of different viruses:
Coronavirus – second most common type, with influenza, and accounts for SARS.
Respiratory syncytial virus
Rhinovirus – most colds are from this.
If that ain't enough, each type has multiple forms, called strains. In fact, there are hundreds of different strains in all!
The Good, the Bad, etc.
It is true that viruses going through the world leave a trail of sickness as they go. But there are possible exceptions.
Take a bacteriophage
Image by "AFADadcADSasd"**
OK, they look like creepy aliens from Mars, but they do have one potentially useful property – they go after bacteria, not people. Some want to use these creatures to fight illness.
Set a thief to catch a thief, as they say. Sounds a bit strange? Maybe not so strange – after all, we are dealing with odd things, things that hinge on the verge of not even being alive after all.
Such is the world of viruses.
On the web
What is a virus? How do viruses work?
This is a fun online animation that recaps most of the points in this lesson.
*Shared by creative commons license 3.0.
**Shared by creative commons license 4.0.
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