Appliance of science: What is a virus?

We are all familiar with the word and we have certainly experienced the down side of them, but what exactly is a virus? Are they any different to bacteria and are there any benefits to sharing our planet with them? Dr Naomi Lavelle has the answers.

What exactly is a virus?

We are all familiar with travelling light, but the virus takes the idea of hand luggage only to the extreme. They literally just contain some strands of genetic material and some proteins. These are the most basic components needed to maintain life. Except viruses can’t exactly maintain life, they need help when it comes to replicating, making more of themselves; they need a host to do some of the work for them and that is why all viruses are parasites!

What happens when we get infected by a virus?

Viruses can enter our bodies by a number of different routes: via our air passages, through an open cut or there are even those that will pigy-back through the saliva of a biting insect. Once inside the virus locates a particular cell and hijacks its machinery. Different viruses use different methods to get inside the host cell, some just inject their genetic material while others are able to enter the cell in their entirety. Once inside they use the host cell’s machinery to make copies of their own genetic code along with new protein components that allow them to package their genes into new viruses.

One infected cell may be used to make hundreds or even thousands of new viruses in this way. Once produced, the cell often bursts, freeing the viruses to infect other cells within the body.

How do we get rid of them?

Thankfully our bodies are well equipped to fight off most viral infections. Our immune system releases an arsenal of defence mechanisms and usually kills off the virus before it takes over the body completely.

Antibiotics have no effect on viruses at all and should not be taken to recover from a viral infection.

Are they living organisms?

Many scientists argue that viruses cannot be classified as living organisms as they lack the machinery required to replicate and they do not perform normal functions such as metabolism (they don’t eat and process food).

What is the difference between viruses and bacteria?

Both are microbes and they can both enter the body in similar ways and cause similar symptoms. However that is where the similarity ends. One main difference between viruses and bacteria is their size. Most viruses are about 100 times smaller than the average bacterium. Bacteria can survive on their own, without a host, while viruses can’t. Bacteria have fully functioning cells with all the machinery necessary to replicate. Viruses do not. Most bacteria are harmless to humans, many are even beneficial.

Are there any good viruses?

It seems not all viruses are bad or harmful. Resent research suggests that some viruses might be beneficial to humans, living in mucus created by our bodies and targeting and killing harmful invading bacteria.

Naomi is a science communicator and mother to three inquisitive children. She can be found at

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