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  • Alex Cloherty

Why don't antibiotics work on viruses?

When I was growing up, we had a sticker on the soap bottle in the main bathroom. It read, "Do bugs need drugs?" I had no clue what that meant when I was 12, but I later found out that the sticker was part of a campaign by our government. In fact, it was at the start of a multitude of public health campaigns across the world which took off during the 2000s to teach people more about antibiotic use. One of the main messages of campaigns like this is: antibiotics only work on bacteria - not viruses. But when I first understood that message, then I wondered: why?

This question gets to the very root of what bacteria and viruses are. Let's start with bacteria - that's an easier question to answer, as you'll soon find out. To start, let's get one thing established: bacteria are amazing. Bacteria each consist of one single cell. One single cell that is even smaller than the tiny cells in your own body. Yet, bacteria can work together as a team, they can 'talk' to each other, and they can perform quite complicated processes within themselves. They are tiny machines which can have 'daughter cells' (yes, we really call bacteria babies daughter cells), trade DNA with each other, and travel around their environments in a multitude of different ways. Bacteria have many different lifestyles, and there are actually only a few whose lifestyle involves infecting us humans and causing disease. Bacteria are way cool, and I hope as you continue to read my blog, I'll convince you of this, too.

This single-celled-ness of bacteria is a key differentiating feature between them and viruses. There is no contention amongst scientists about whether bacteria are living, just like us. Nobody in the scientific community, as far as I know, thinks that bacteria are non-living. Non-living entities are things like rocks, or candles, or your favourite stuffed animals.

This is a picture of my favourite stuffed animals. In order from left to right: HIV, a T4 bacteriophage, a white blood cell, Helicobacter pylori, and swine flu. The black plague has mysteriously gone missing. If you want one of these for yourself, you can buy them at, one of my favourite nerdy websites.

Viruses, on the other hand, are contentious. Some in the scientific community think that they should be classified as living. I am on this side of the argument because viruses can self-replicate to produce little virus kids, they can evolve over generations, and they interact with and respond to their environments . To me, these collective facts make viruses seem a lot like all the other things we classify as living. But there are many scientists who think that viruses can't be considered living. One of the main arguments behind this is that viruses absolutely need a "host" to do most of these things that make them seem to be alive. This host can be a bacterial cell, a human cell, a dog cell... Across the wild and wonderful world of viruses, viruses collectively can invade pretty much every type of cell.

Viruses need host cells for one major reason: on their own, they simply don't have all the stuff they need to do the stuff they like to do. Viruses are like hijackers: they often don't own the right machinery, so they steal it. Specifically, they steal it from their host cell. One lonely virus can't do much on it's own aside from hang around useless like the ever-irritating Damsel in Distress until Prince Charming Cell comes along, so many biologists think it simply can't tick the necessary boxes to be considered "alive".

This concept of virus-as-useless-damsel gets us back to why antibiotics don't work on viruses. Antibiotics usually work by attacking very specific machines that bacteria have, which are necessary for the survival of those bacteria. Antibiotics are designed to attack machines that bacteria have and that human cells do not have: that way, the drugs don't damage our cells and specifically mess with the bacteria. Viruses, however, don't have the same machines as bacteria!

Why don't we just make things to target virus machines then? Well, we do. For instance, Tamiflu can be used against the influenza virus, which causes (you guessed it) the flu. But, it's a lot harder to design treatments to target virus machines. Why? Viruses have far fewer machines than bacteria, because they steal our human machines! This complicates things, because if we try to mess with the major machines that viruses are using, we then mess with our own machines.

So, the take home message of this article? I'll sum it up for you below.

First, viruses are tricksters, and bacteria are cool.

Second, If you have a cold caused by a virus, drinking lots of water and sleeping a lot will likely help you a lot more than taking antibiotics! But of course, if you're not sure if you have caught something that is viral or bacterial (it's hard to tell without running certain tests in a laboratory), check with your doctor.

I leave you this week with a challenge. Next time you're sick, think back to that sticker on my childhood soap bottle and think: Do my bugs need drugs?

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