Where do sexually-transmitted diseases originate?

Chris - Wherever there is an ecological niche something will spring up to occupy that niche. When you've got an opportunity for spread to occur and you've got humans coming into close contact - it doesn't matter if you're kissing someone and spreading Epstein-Barr virus that causes glandular fever or you're talking about other viruses and bacteria that can spread sexually - there is an opportunity for spread to occur and you have a certain environment which is coming into contact with another environment. That means there's an opportunity for anything that can tolerate those environments or exploited to spread. Because you have those opportunities and that contact anything that becomes able to exploit that environment will do so. That's just nature. If as viruses and bacteria evolve and change to exploit those environments so they become specialised to do just that. If you look at Neisseria meningitides, the bacterium that causes meningitis, it's got a relative called Neisseria gonorrhoeae. In other words the same kind of family, the same species of bacteria can cause bacteria down there and meningitis up there but if you move one to the other location they can cause a sort of similar infection and similar manifestation in both places. If someone gets Neisseria meningitides down there then instead of meningitis they can get a bit of an infection. Kat - Do you think we are winning against bugs or they're winning? It seems to be an evolutionary arms race. Chris - Ever since life got started there's been a furious arms race going on with each organism on the planet trying to secure its own patch of turf because there's only so much energy to go round. There's only so much chemistry to go round and if you've got it someone else hasn't. As populations increase you will see competition between one group of organisms or one entity trying to rob energy or exploit the system better than anyone else. In order to keep up everyone has to change. It's a bit like radio station changing to digital. You found people buying very expensive equipment that could make your sound a bit louder than the person who was running the radio station next door. The radio station then bought a bigger box that would make them louder than everyone else. Before you know if=t you've got this compression war going on where people are seeking to be louder than everyone else. Now people are saying now we've got the audio so loud we're going to make our station distinctive by being quieter than everyone else. It's the same with microorganisms. They're going to change and adapt in order to shift and exploit the circumstances as they exploit themselves. We're never going to have an end to this arms race.

Kat - Do you think we're due another massive flu pandemic or Black Death plague?

Chris - History has a habit of repeating itself there's absolutely no doubt about that. We know that flu pandemics come roughly every 30 or 40 years. There's no doubt that there will be another one. Whether there will be a major manifestation or not we don't know because the Earth is a very different place now than it was in the past. We've got half a million people airborne in aeroplanes at any instant in time. No city is more than 24 hours from any other city which means that's less than the incubation period for most infectious diseases. At the same time we have more people on Earth - nearly 7 billion than we've ever had before and living in higher density than we've ever had before. This is the time, if there's ever going to be one, that we're going to see some kind of infectious outbreak.