Bacteria vs viruses

Posted on 3 May 2016

Ever wondered why antibiotics don’t do anything to fight a viral infection? As a Mediclinic anatomical pathologist explains, it’s because bacteria and viruses are completely different things. Knowing the difference will help you get the right treatment.

Coughing, sneezing, fever or fatigue could all either be symptoms of a bacterial infection or of a viral infection. For doctors, the challenge lies in working out which one of the two it is. Biologically, there’s a huge difference between the two – and your treatment will depend on whether your body is reacting to bacteria, or being attacked by a virus.

The important thing to know is that they’re completely different organisms, from completely different branches of the tree of life. When it comes to infections, you’re usually dealing with one of four types of organisms: bacteria (eg. strep throat), viruses (eg. common cold), fungi (eg. ringworm) or parasites (eg. tapeworm). Let’s focus on those first two.

‘A bacterium is a living organism. A virus is not,’ explains Dr David Laing, an anatomical pathologist at Mediclinic George. ‘A virus is basically a collection of either DNA or RNA. It’s just substance. It’s not a living organism.’ A bacterium, meanwhile, is a relatively complex, single-celled microorganism. Most bacteria are harmless – and some are actually quite useful to your body (the ones in your intestines, for example, help your body to digest food).

‘That’s the fundamental difference between those two,’ continues Dr Laing, ‘and that’s why you don’t treat a virus with antibiotics: it’s not a living organism, so an antibiotic won’t kill it. A bacterium, on the other hand, is a living organism, so an antibiotic will kill it.’

It’s important to note that an anti-bacterial will only affect a bacterium – not a parasite, not a fungus, not a virus, and not a host. Medications like antibiotics or anti-bacterials work on what’s known as selective toxicity. This means that they target specific areas in the organism, and are not harmful to the host. And that’s why, if you have a bacterial infection, the antibiotics your Mediclinic GP prescribes for your will kill the bacteria without killing you!

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In the interest of our patients, in accordance with SA law and our commitment to expertise, Mediclinic cannot subscribe to the practice of online diagnosis. Please consult a medical professional for specific medical advice. If you have any major concerns, please see your doctor for an assessment. If you have any cause for concern, your GP will be able to direct you to the appropriate specialists.

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