Question of the Week

Are city dwellers more immune to bugs?

Thu, 9th May 2013

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Question

Jeremy Eaton asked:

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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No they are not because people who are in the city are around more people, which increases their chances of getting a bug. However, that doesn't exempt country people from getting it either. City people are just more likely to get a bug. Patricia92, Sat, 11th May 2013

You didn't answer the question Patricia. It wasn't 'do they get more bugs' but are they more immune to the diseases bugs transmit . I assume the answer must be that herd immunity will be higher due to more infections available to cause antibodies to be created. Measles is a good example; it killed native peoples who had never encountered it but was a relatively mild disease in Britain due to herd immunity gained over centuries. That this immunity - antibodies passed on in mothers' milk - now no longer exists due to the introduction of MMR vaccine illustrates the point, and further, I think, suggests if it's not too serious leave well alone, it's what our immune systems are for. But that's of no interest to multinational drug companies with their 'Three for the price of one' offers that politicians just can't refuse. Easier to blame it on a maverick doctor who thought he saw connections to autism and who has never been persuasively rubbished despite the concerted campaign mounted by governmnt and medical establishment. Makes you think.

I had measles as a child as did all kids, never heard of any being anything more than slightly feverish. My eldest child had measles vaccine in the sixties and got full blown measles and was in bed for a week with high fever, and then gave it to his younger siblings. Progress anyone?

But back on topic, there's so much travel these days that living rural doesn't mean never mixing in cities, so occasional visitors may be more at risk of getting ill because of less exposure.
Peter the painter, Tue, 14th May 2013

This immunity would fair well if there were no people visiting the city from outside the city, this was proven years ago when westerners visited an isolated native settlement on an island, the naitives soon developed measles and other nasty infectious deseases, they had never ever encountered such viral infections before, so were not immune and soon came down with fevers, some dying in this process. confusious says, Tue, 14th May 2013

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