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Asked by to Bethany, Keith on 19 Jun 2014. This question was also asked by .
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Bethany Dearlove answered on 19 Jun 2014:
This is a hard question, and depends what you mean by ‘more’ diseases. Most infectious diseases change over time, and often this changes how they behave. One of the most noticeable effects of these changes it that they allow the bug to fool our immune system, so we can get re-infected with the same disease. This is why we have to have a new flu vaccine every year, as the current flu strains are different to those which circulated last year. Sequencing allows us to identify these different strains much more easily, meaning we can now discover them a lot more quickly. For most microbes, you’re probably looking at 1-2 years for a distinct strain to appear. For example, during the course of my PhD, there were two types of norovirus common in humans – one that originated in New Orleans 2010, and one that originated in Sydney in 2012.
As for new diseases, I read somewhere that there’s been at least 30 new types of infectious disease discovered in the last twenty years…and these are just the ones we’ve been able to characterise in multiple people. That’s actually quite a lot of diseases, when you think how much treatments have progressed in the last 50 years. Of course, the fact we’re getting better at diagnosing diseases all the time means that we’ll continue to discover more and more, even if they’re rare.
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Keith Grehan answered on 22 Jun 2014:
As Bethany said this is tough question because diseases like bacteria and especially viruses change so quickly it can be hard to decide when they have changed so much that we have to think them as new diseases.
So while we think of flu as just one disease there are lots and lots of strains and we are definitely finding new strains, most recently two new strains of flu have been identified in bats. These have been called H17N10 and H18N11 and they don’t seem to be able to infect humans.
More seriously the recent outbreak of Middle Eastern Respiratory (MERs) was a new virus that we hadn’t known about before. It’s really tough to know if when we first identify a disease if it is really new or if this is just the first time we have had the tools to identify it and study it. It’s important to realise that as research moves forward so we invent better and tools and procedures this makes it easier to identify new disease and sometimes this lets us identify things that made people sick in the past. A good example is the 1918 flu outbreak, although this was a horrible disease that killed millions of people at the time no-one knew what the actual disease was since at the time we had no way to isolate and examine viruses. It is only by using modern methods and tools to analyse samples from that time that we have been able to identify it as a flu.
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