Disease and Evolution
The human body has been plagued with diseases since the beginning of time—pathogens like viruses and bacteria have made us privy to Mother Nature. As humans evolve, so do the diseases we are susceptible to. Some diseases that were once rare have become common, others have disappeared and newer, more daunting ones have emerged. Many of these changes have taken place in the wake of important transformations in human civilizations and ecology. It is therefore feasible to propose that diseases succeed and fail in response to humanity's advances. Natural selection is unable to provide us with perfect protection against all pathogens, because they tend to evolve much faster ...view middle of the document...
In order to be successful as a pathogen, there must be a balance of transmissibility and effect on host fitness.
Knowledge of microbial genomes, and the functions they encode, is severely limited. Among 40 phyla of bacteria, for example, most of the available genomic sequences were from only three phyla; sequencing of Archae and Eukaryote genomes has proceeded in a similarly sporadic manner (WHO, 2007). However, pathogens like virus, bacterium, prion, fungus, viroid or parasite are known to cause disease. Bacteria are typically 1- 5µm. In fact, a vast majority of bacteria are considered harmless or beneficial to humans. They are living prokaryotes and cause disease from parasitism or toxin production. Some common examples of bacteria causing disease are Tuberculosis or being exposed to Anthrax. On the other hand, viruses are also big players in the world of disease. Typically only 20-300 nm, they are interestingly the most abundant type of biological entity. They are acellular and cannot replicate on their own. They cause disease by hijacking a cell’s machinery. They have no energy metabolism, do not grow, produce no waste, and do not respond to stimuli—so are they living? That is a hot debate topic in the world of Science. What we do know is that viruses are behind some of the deadliest diseases in our world including Ebola, SARS, HIV/AIDS.
The Ebola Virus and Evolution:
The Ebola outbreak in West Africa has international medical organizations on high alert and people all around the world on the edge. Ebola is normally carried by animals like fruit bats, but occasionally makes the jump to humans. When it becomes apparent in humans, it is fatal, killing more than half of those infected. However, because it is only spread by direct contact with bodily fluids, most of the world need not fear for their lives. An important question to ask though is whether Ebola virus can evolve.
The Ebola virus is experiencing plenty of mutations. Ebola has RNA, not DNA, as its genetic material. When RNA is copied, many more mistakes are made than when DNA is copied. This gives viruses like Ebola a particularly high mutation rate when compared to DNA-based viruses like smallpox or chickenpox — though not as high as the rates at which HIV and the flu accumulate new mutations. This indicates that Ebola's high mutation rate and its rapid rate of replication may cause the virus to evolve quickly (Carol et. al, 2013). Ebola (at least the strains that we are most interested in) now live in humans, which have many physiological differences from bats. The quick pace of evolution in the recent Ebola outbreak may in part reflect the initial stages of the virus' adaptation to humans, as natural selection favors mutations that make the virus more successful in its new host (Gire et. al, 2014). It is difficult to diagnose Ebola infections and hampering the medical community's ability to treat and contain the virus. Such changes could also impact vaccine development and...