For we know that the whole creation groaneth and travaileth in pain together until now.
Romans 8:22
"Many infectious diseases can be traced back to the decay and corruption of the original created design of microorganisms as a result of the Fall. Corruption literally means to destroy (from the Latin corruptus).
The origin of pathogenic (disease causing) bacteria such as Y. pestis is complex and multifaceted, and may be explained by a combination of genes that were lost, added and moved. 
The story of Yersinia’s degeneration into the plague pathogen may serve as a model of ‘fast’ genomic decay and corruption.
It appears that the beginning of pathogenicity in the genus Yersina started with a net loss of chromosomal DNA from its original ‘kind’.
Later, there were minor additions of plasmid DNA3 as well as DNA from gene from another organism, Y. pestismade a crucial shift in its host range, allowing it to survive in fleas, and devolved to relying on its blood-feeding host for transmission. This is just another example of the flexibility of many microbes in sometimes repackaging themselves into more dangerous agents of infectious disease.
This last corruption is one that distinguishes Yersinia pestis from all closely related, more benign bacteria such as Y. pseudotuberculosis and other Yersinia (e.g. Y. entercolitica).
In turn, as Y. pestis adapted to rely on its new blood-feeding host for transmission, the emergence of more deadly bacterial strains would have been favored. It appears that these minor plasmid additions were the last changes made in an otherwise long series of genetic losses in Y. pseudotuberculosis’ chromosome.
One pathogenicity island was acquired by Yersinia pestis from a different bacterium. This cassette of genes was not the result of evolution of new chromosomal DNA, but was an acquisition through lateral gene transfer.
It produced a c o r r u p t e d m e s s a g e t h a t g a v e bacteria a new ‘position’ in the gut. Y. pseudotuberculosis, which lacks the hms locus gene inhabits harmlessly the mid gut of the flea. Plague bacilli, by contrast, have this inserted locus gene. Free from their original control, causing a lack of ‘good’ ‘direction’ information, the bacteria migrate from the mid gut to the fore gut, forming a plug of packed bacilli which is passed on to the victim when the flea feeds.
Plague bacteria are not the only microorganisms that have 
degenerated into disease-causing organisms.
A more common recent example of a harmless bacteria ‘devolving’ into a pathogenic one is the intestinal Escherichia coli O157H7 strain that occasionally causes fatalities.
Other pathogenic bacteria that have undergone genomic decay include various mycoplasmas (e.g. Mycoplasma genitalium and M. pneumonia, the later causing pneumonia), and Mycobacterium leprae (the leprosy bacillus).
As we study the origin of infectious disease from a creationist, Biblical perspective, bacteria provide us with a model of what happened to living things over time in a fallen, cursed and corrupted world. Many ill-nesses can probably be traced back to a loss of genetic information, plasmid acquisition, and gene translocation in organisms such as bacteria, fungi, etc. For those who know the Creator, we can rejoice that someday the Great Physician will restore all plagued bodies to a very good condition once again (Rev. 22:2–3)." CMI