Viruses

Here are a few things that are alive. And some that are not alive. And here is something... in between. It doesn't use photosynthesis, like plants, and it can't eat, drink, or grow.

It can do only one thing: reproduce. However, it can't do this by itself. This is a virus. A virus can look like this. Or like this.

Or like this, for instance. There are many different kinds of viruses, but all of them are built the same way: A shell of proteins, and inside the shell - the genes of the virus. The genes describe how a new virus of the same sort is created. Because this is all that a virus does. It reproduces.

But how does a virus reproduce? And why can it make us ill? Well, to reproduce, a virus needs to find a living cell, and hijack it. The virus enters the cell, infecting it. The cell is supposed to use its own genes, and produce what the cell needs, or something that it will send to other cells.

But when the virus is in control, it orders the cell to use the genes of the virus instead. And so it does. The virus forces the cell to produce new virus particles. Tens of thousands, sometimes hundreds of thousands. This way, the virus reproduces.

At the same time, the cell dies. Viruses can't move. They fly, float or stay still, until they are lucky enough to come across just the kind of cell that they can hijack. Viruses are really choosy. They usually match only one sort of cell, for instance a liver cell in a human, or a leaf cell in a tobacco plant.

This is why viruses normally don't spread between species. Humans have their viral diseases, dogs have theirs, birches have theirs. What ails you when you have a virus infection is first and foremost your own immune system. It battles the virus, which it identifies as an intruder. The immune system can change the body temperature and the blood flow, or produce substances that fight the infection.

This can give you fever, nausea, or body aches. Often your immune system incapacitates the virus. For example when you get the common cold. After a few days, you get well. But there are virus infections that won't go away for a very long time, or will never leave.

They become chronic. This is the case with some liver infections, and HIV. There are also viruses that can hide in the body, and create symptoms again, though you feel well in between. This is how herpes and chickenpox viruses work. They can stay latent in the body.

And then there are viruses that disappear, but can leave traces. One example is HPV, that can damage cells in the cervix and cause them to later develop into cancer cells. But aren't there medicines against viruses? Antibiotics, for instance? Nooo!

No, no, no. Antibiotics are great if you are infected by bacteria and other living organisms. But they don't help at all against viruses. And it's extremely important that we only use antibiotics when they are really needed, and make a difference. The more antibiotics we use, the more organisms - such as viruses - become resistant to antibiotics, and the medicines don't work anymore.

So: No antibiotics against viruses. The best weapon against viruses is vaccination. While using vaccines smallpox has been exterminated, and soon polio might be gone too. Measles and rubella, serious diseases that can be deadly without treatment, have become a lot rarer, thanks to vaccines. Vaccines train the immune system, so that it can quickly defeat intruders that enter the body.

Lots of research is dedicated to finding new and better medicines against viruses. But for now: Hooray for vaccines!