Are city dwellers more immune to bugs?

09 May 2013

Question

Are you more immune to disease if you live in a dense population, because you are exposed to more and different types of bugs?

Answer

Eleanor - So in principle, yes. People living in small isolated communities may experience a more limited number in diversity of infections and they can lack immunity to diseases which are actually quite common place in other environments. Some classical examples are those with epidemics of diseases such as measles and smallpox in small Amazonian communities when they first came into contact with outsiders. But these days, human populations are so mobile that actually, very few of these really isolated populations persist and you're as likely to contract the latest strain of flu whether you live in a huge city or in a smaller town or village nearby. And that's because people move around between these communities on such a regular basis that they move the virus around with them and we only have to look at how quickly the swine flu epidemic in 2009 reached almost every country in the world, including countries with really low population densities. And we can see from that that actually, from the perspective of the bug, we all now live in a single global community our immune resistance will reflect the fact that we are all exposed to very large numbers of infections.

Hannah - So, with frequent global travel, there's no rationale for rushing to live in the city since it won't boost our immune systems. However, pollution and stress from the city have both been linked with weakened immunity. Plus, there are studies that show that people who grow up in cities process stress differently and have an increased risk of getting mental health disorders such as Schizophrenia.

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