|MadSci Network: Medicine|
>How can a body recover from this massive
>kind of injury?
There are many ways to aspects to this question. You are correct that it is very difficult if not impossible to recover from a full-blown infection with an aggressive filovirus. You can get a tremendous amount of damage to the vital organs. The cumulative effect of all that damage, if extensive enough, can definitely be irreversible and lethal. But realize that many tissues have a large reserve capacity (you can lose a lot of your liver and still have plenty left to serve the essential functions), some tissues can regenerate themselves to a degree, and in essentially all cases the decrease in tissue function will be greater during the infection (i.e. active inflammation) than after healing. It may be useful to consider the infection as having a 'critical phase' in which tissue damage will be at a peak, resulting from the combined effect of viral cell killing, tissue damage from blood vessel leaking and clotting, and damage from the immune/inflammatory reaction the body mounts.
So why might some people be able to make it past that critical phase? Realize that Ebola virus itself, and certainly the filoviruses as a larger group, are not a single virus. While they all infect the reticuloendothelial cell system, they follow the rule among viruses that there is great heterogeneity among strains and rapid evolution. And for many reasons, many of which we understand very poorly for the filoviruses, different viruses and strains are more aggressive or 'virulent'. That is to say that they may reproduce themselves faster, infect a greater variety of endothelial cells, evade the immune system better, be better at killing cells, and so on. So while there are definitely many people who appear to have been infected by Ebola type viruses in the past and survived (evidenced by antibody testing) these are presumably not the same and very virulent strain of Ebola virus that caused the "outbreak" not long ago. In fact, the distinctions among the different strains and species of virus are a matter of constant debate and investigation.
The other difference between a good and bad outcome of infection may lie with the person infected - we call these 'host factors'. There are many host factors, but the most important relate to the immune system. This is certainly very complicated, but in general it is clear that some people mount a more effective immune response to certain 'pathogens' than others. That is, they recognize and kill the infecting bacteria or virus more efficiently. Paradoxically, though, it can also work the other way - that is to say that sometimes reacting against the virus can be BAD, since the resulting inflammation may be worse than the infection itself !! People fill textbooks trying to explain these differences, but the bottom line is that you and I may not get sick to the same degree, even if we are infected with the same strain of virus.
I hope this helps answer your question. Since I seem to be getting a lot of Ebola questions on MadSci Network, I feel it only fair to say that I definitely do NOT consider myself an expert on this virus! In fact, I must admit to having been somewhat in error on my last answer, since it seems that filoviruses are able to infect a greater variety of cell types than I had originally been taught!! I do have a thorough understanding of basic virology and medicine, though, and have tried to answer this and the previous questions from that basis. Simply put, Ebola virus can and must be considered by the same 'rules' as any other infection. There is a lot of good literature out there on the internet about Ebola, and I encourage you to peruse it (try ebola on any search engine - you'll be amazed). There is also a lot of garbage!! The hype that surrounded the recent outbreak, the movie 'Outbreak' (entertaining, but scientific hogwash), and all the rest has resulted in a lot of misinformation and fantasy. So read on, but be skeptical.
Anyway, thanks for reading the Mad Scientist.
Tom Wilson, MD PhD
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