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Asked by Thomas B to Ceri, Marikka, Matt, Rob, Sally on 10 Nov 2014.
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Robert Hampson answered on 10 Nov 2014:
Throughout history, viruses generally cause larger and more infectious pandemics as they spread more easily (e.g. Spanish flu in 1918, the current Ebola crisis is also caused by a virus). Bacteria generally cause smaller, slower, but more lethal pandemics as they are often less infectious but more dangerous to those infected (Bubonic plague or Black Death was caused by a bacteria called Yersinia pestis). However, this is a massive generalisation.
The issue at the moment is we’ve never really had truly effective medicines for viruses so our society is designed around them existing (people get a cold or the flu and the avoid work/school for a couple of days). However, for nearly 100 years, we have had very effective medicines to treat bacterial infections and our society has changed to take this into account. Much of medicine relies upon the assumption that bacteria can be quickly and effectively treated.
When these medicines become ineffective (this will happen) there will have to be a change to learn to live alongside bacteria again or we will have to very quickly come up with more effective treatments for bacteria.
For viruses to become more of a problme, we are waiting for them to mutate to either infect humans more easily (which may increase the number of ill people but it may still only be as serious as a cold or flu) or for them to become more dangerous to those infected with them. However, often it isn’t particularly effective for a virus to quickly kill the host as it then struggles to pass on the infection to other hosts.
I think bacteria therefore are likely to be more of a problem.
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Sally Cutler answered on 10 Nov 2014:
Hi Thomas,
This is a pretty big question. Viruses, especially those with RNA genomes are more error prone in their multiplication and therefor vary and evolve more quickly. This is important to those which have recently made host species jumps like HIV virus adapting from apes to humans. Guess you also need to think what is the bigger threat – to be killed or carry infection without being killed so that you can continue to spread infection. I think here you could compare Ebola vs HIV even though both subvert your immune system. In very general terms, bacteria often result in more life-threatening conditions. Sometimes these can also work together like when you have a viral respiratory infection allowing a bacterium to take hold and cause pneumonia. The bacterial infection is the more serious, but needed the virus to pave the way. Hope this helps. -
Ceri Dare answered on 10 Nov 2014:
Good question, and it’s hard to tell. We aren’t very good at treating viruses – mostly we just look after people who are ill with them, until their immune system can fight them off. At the moment we can treat most bacterial infections with antibiotics, but as you know then bacteria are becoming more resistant to antibiotics.
The thing that would probably kill most people in Europe isn’t the direct effects of a disease, but the problems of society breaking down – if supermarkets don’t deliver food every day, then the shops will run out in a day or two. Hospitals might not be able to look after people with ordinary illnesses if too many people have an epidemic disease. If workers stayed at home to avoid catching an illness, electricity, gas etc would stop working. So I would say the biggest threat is not being prepared. You can find out more about emergency planning in the UK here: https://www.gov.uk/terrorism-national-emergency/national-emergencies
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Matt Bilton answered on 11 Nov 2014:
Really interesting question. If you’ve seen the film Contagion then you’d probably say virus. Certainly, the 1918 flu pandemic was pretty horrific. To put it in context, about 16 million people died in the first world war from 1914-1918 – whilst about 50 million people died from the flu in 1918. This is why the threat of pandemic flu is so scary, and the swine flu pandemic was taken so seriously even though it wasn’t quite as bad as feared. Or take another virus, HIV/AIDS, which kills ~1.6 million people every year. This is more than any other single infectious agent.
By contrast, about 1/3 of the world’s population (~2-2.5 BILLION people!) are thought to be latently infected with tuberculosis bacteria. Every year, ~1.5 million people die from tuberculosis – more than any other single pathogen except HIV. And it kills that many people despite the fact it’s mainly curable! Before antibiotic treatments for TB were discovered, tuberculosis killed on average about 70% of those who become sick. TB – caused by bacteria – was the leading cause of death in the Western world. Now, currently hard to treat, and even impossible to treat antibiotic strains of TB bacteria are on the steady increase. And of course the problem of antibiotic resistance exists for all sorts of potentially lethal bacteria for which there are currently treatments, not just those that cause TB.
So I think that in the long term, the issue of antibiotic resistance could cause the greater impact to public health – although if I was worried about a sudden global event, I think I’d be most worried about a respiratory virus, like the flu. In any case I wouldn’t panic…although maybe best not to put down the pipette just yet. Best get back to work!
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Marikka Beecroft answered on 12 Nov 2014:
That is an interesting question! To be honest with you there is no clear defining point that makes one more deadlier than the other and each one has big killers on their side! Viruses have things like HIV, flu and smallpox (though it’s been eradicated) and bacteria has tuberculosis, pneumonia and MRSA that kill loads of people everyday. One thing I can say is this, antibiotic resistance is tipping the deadliest factor towards bacteria: if we can’t treat them how can we stop them from killing us? It, to me, is the bigger threat as we depend heavily on antibiotics in our healthcare system and need to discover new antibiotics and new ways to treat different people.
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