Historical studies of infectious diseases may help guide modern health sciences to recognise methods for controlling diseases as infectious agents spread and evolve over time. An understanding of these evolutionary effects helps in understanding why some pathogens cause more harm than others and the human activities that can prevent the harm. The prevailing dogma was that disease organisms eventually should evolve toward benign coexistence with their host. But now the evolution has been broadly investigated by a theoretical framework that is based on the principles of natural selection.
It provide s insight into the true scope of infectious causation of chronic disease and a sense of , which diseases can be prevented or cured by disease control strategies such as vaccines and antibodies. It has been confirmed after various studies that vector-borne pathogens are more lethal on a per-infection basis than the directly transmitted pathogens. A comparative study of vector-borne pathogens indicates that this greater virulence is related to the adaptation to the conditions of vector-borne transmission.
Evolutionary theory predicts that pathogens that can be transmitted from immobilized people should evolve to relatively high levels of virulence. The process of virulence management can be achieved by a virulence antigen strategy. This strategy states that vaccines should be based on virulence antigens which functions by making mild but transmissible organisms harmful. The virulence antigen theory differs from the traditional approach to vaccine development as the latter selects antigens on the basis of the protection conferred to study subjects regardless of whether the antigens are virulence antigens.
By selectively suppressing the virulent variants, virulence antigen vaccines force the target pathogens to evolve toward benignity. An interesting case is of sexually transmitted pathogens. They are characterised by adaptations that allow them to evade the immune system to persist in and be transmitted from the body. The sexually transmitted pathogens are moulded by natural selection to be benign over the short run. But this long term persistence within host raises the possibility of long term damage, even though there is low probability of severe damage during any small period of time.
Zoonotic diseases generally have limited potential for spread in human population with AIDS as the only exception. The article provides a good insight on the pathogen’s transmission mechanism, their evolution and logic on becoming epidemic or endemic causing mass destruction of human population. The history and the effect of pathogens have been discussed in detail. It is a very insightful work to help prohibit the evolution of highly virulent pathogens. This is also useful in finding ways to contain the transmission and spread of diseases.
The facts are supported by enough examples from the past. The new method of virulence management by virulence antigen strategy is really very effective as circulating benign strains may protect unvaccinated individuals and the population as a whole against the spread of harmful strains. In my opinion I feel that a more elaborate dealing is required for diseases like diabetes, ulcers, cancers etc. It is very difficult to draw an inference on chronic diseases and their relation to pathogens. Over the article is very insightful and enriching.