We all travel more than at any other time in human history – planes and trains, cars etc, along with people travelling abroad for work means that most adults are always on the go. We all know what this means when it comes to climate change, but did you know about some of the other affects of humans travelling so much? Disease. All this travelling helps diseases to spread, and not just through the human population.
Recently we have learnt that the “Ash dieback” fungus has appeared in Britain. This fungus affects (unsurprisingly, given the name) Ash trees. Denmark has reported that 90% of all its Ash trees have been killed by the disease. Can we be sure that people bought this disease to the UK? Well we’d need disease scientists to answer that, but when you go to an area with a disease, you can carry that disease either by catching it (unlikely in this case!), or bringing back part of the disease itself (fungi in this case) on your clothes, in your hair, on your shoes, etc. There is also a danger of insects being accidentally carried by you or in your bag. This is why planes from Africa get bug sprayed before they come back to Europe – if mosquitoes or other dangerous insects were able to survive the journey we could find diseases such as malaria or dengue fever back in Europe, so the planes are sprayed to make sure that that doesn’t happen.
Looking back through history, palaeontologists and archaeologists can identify times when mass movements of people have carried disease across the world. It is commonly known that smallpox carried by Spanish invaders pretty much ended the Aztec and Inca empires of South America as smallpox had never been seen in that part of the world before. So, the immune systems of the local populations were not able to deal with this new pathogen (it did kill a lot of people in Europe too, but don’t worry, these days we have a very effective vaccine).
It goes back further too. When humans first left Africa we can see in the fossil record that where humans went, animals went extinct. There are three main theories about why we see this so clearly in the fossil record; either humans carried diseases that were caught by animals; or humans hunted too many animals, so the populations got too small to survive; or habitat loss, where humans cut down too much of the environment where the animals lived. This was tens of thousands of years ago, how little has changed since then!
Of course we’re not saying that you should never travel (especially by environmentally friendly ways like taking the train), we at Roots & Shoots just find this very interesting, and it’s certainly something to think about. Just make sure that when you do go somewhere you follow the advice of the local health authorities – if they tell you that there is a disease outbreak in an area that you are going to and that you should wash your boots and clothes before you leave, then please do!
Free images from FreeDigitalPhotos.net
Blog post by Linda Seward of Seward Technical Writing, providers of original science content.