Plague Time: How Stealth Infections Cause Cancer, Heart Disease, and Other Deadly Ailments

Rating:
Summary: Insightful
Review: This is a great read. Paul Ewald points out quite convincingly that medical professionals neglect the evolutionary side of disease. His theory is that most diseases including chronic diseases like some cancers and heart disease are caused by infections by micro-organisms. This is not to say that his theory is conclusively demonstrated but rather that it rests on principles that are sensible and possibly correct. Another of the important themes talked about in his book is that the virulancy of an infectious agent will evolve depending on how easily it is transmitted. An organism (bacteria or virus) in the human body is always trying to balance its fitness in reproducing in its host versus its fitness in being able to jump into another host. The outcome is decided by natural selection. Whatever evolutionary path results in the most offstring will win out. An organism which reproduces too quicky and imediately kills its host will not be very capable of being transmitted to another host. Take for example the common cold. If the effects of the common cold were much worse then people would stay home from work and the chance of the germs reaching other hosts would be much less. Ewald in fact advocates that people should stay home from work when they get a cold or the flu. This would probably benefit the employer in the long run because the flu would be less prevalent and less workers would contract it. I won't try to argue his points here but I find them quite convincing. On the other hand there are some down sides to the book. As mentioned in some other reviews the title is a bit overstated. Ewald has a theory and not conclusive evidence that things like cancer and heart disease are caused by infectious agents. Some things like cervical cancer and peptic ulcers have been shown to be caused by infectious agents in just the last few years where as the popular belief in medicine was that these were not infectious diseases. However that is not to say that all cancers and diseases are caused by infectious diseases. Ewalds obviously acknowledges this but nonetheless makes some pretty bold claims. Overall I highly recommend the book to non-specialists like myself who want to learn about infectious diseases and evolutionary biology.