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Post-polio syndrome

I'm not a doctor or a researcher, and I have no idea whether this has any connection to some ME patient's conditions. I know a Polio-like illness was suspected to be the cause initially, and that Dr Chia thinks other enteroviruses are to blame, but apart from that there doesn't seem to be much interest in this area in terms of ME research.

I didn't write this blog to stir all this up again, but rather because I find the Post-polio syndrome fascinating. I started thinking about it after reading Disease: the Next Big One, in which the author talked about the difficulties early researchers had in identifying viruses as the cause of diseases such as polio. Another chapter discussed why some viruses are more likely candidates to be the Next Big One (global pandemic) than others.

Apparently one of the relevant factors is the difference between DNA and RNA viruses: the former having lots of genes but mutating slowly, and the latter having few genes but mutating quickly, This is due to the differences between DNA polymerase and RNA polymerase: the former is much more reliable at copying genes, so fewer mutations occur. The author suggested that this often leads to differing survival strategies for each type of virus. DNA viruses, being 'sneakier' (my term), often use their ability to incorporate the genes of the host into their own genome to subvert the immune system, and thereby establish persistence in the host organism. RNA viruses, on the other hand, don't have the same ability to incorporate host genes (because RNA polymerase's unreliability puts constraints on the size of the genome) and therefore have to rely on 'shock tactics' (my term again), resulting in more virulent, but shorter lasting infections. Examples of the former (DNA viruses) include the herpes viruses; examples of the latter include Ebola, Marburg, and the Influenza viruses.

This made me think about Dr. Chia's enterovirus theory. I knew enteroviruses are RNA viruses, so I wanted to know if other RNA viruses were suspected of causing chronic infection. HIV is a very prominent example of such a virus, but I don't know enough about retroviruses to know if these are an exceptional case.
I then looked up polio (which is a member of the enterovirus family but is often treated with separately in the literature) and started reading about Post-polio syndrome. It amazed me that the cause is still unknown; this was one of the first viruses to be identified, and one that is no longer a real danger in the West, thanks to the polio vaccine.

Several theories have been proposed to explain Post-polio syndrome. The one that interested me the most was the idea that it is caused by persistent, albeit mutated, polio viruses. The two papers below are fairly recent and cover in vivo and in vitro persistence, respectively.

http://www.researchgate.net/publica..._survivors_diagnosed_with_post-polio_syndrome

http://www.ncbi.nlm.nih.gov/pubmed/9645992

I started thinking about the possible parallels between the initial difficulties researchers had in proving that viruses were the cause of illnesses such as Polio, and the current difficulties researchers have in proving that persistent infection is the cause of chronic illnesses such as Post-polio syndrome.

Post-polio syndrome might prove an interesting test case of the latter theory: if it is proven to be correct in this case, doctors and researchers might be more open to the idea of persistent infection in other chronic illnesses such as ME. Unfortunately, some of the same factors that discourage research into this area in ME are also at work in the case of Post-polio syndrome: it is a relatively unfashionable area of research, and its victims find it difficult to make their voices heard. Polio has the additional problem that it is seen as largely a Third World issue.

Despite these problems however, Post-polio syndrome has the potential to make us rethink our approach to chronic disease.

Comments

My husband has Post Polio. I'd understood it to be due to death of nerve fibers which had regrown weaker after the illness. But it seems more like ME, with fatigue, weakness. Maybe your explanation relates to some of his cognitive decline, also.
 
I'm sorry to hear that. It's not my explanation, and it doesn't seem to be widely accepted yet, but perhaps work like this will one day allow doctors to help people with Post-polio.
 

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