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Understanding Epidemics
John Brooke
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eBook - ePub
Understanding Epidemics
John Brooke
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About This Book
This book explains, in non-technical terms, the relationship between man and the many bacteria, viruses and other micro-organisms with whom he lives in the most intimate manner throughout his existence. It is explained that for the most part, this coexistence is beneficial, but that through evolution and natural selection, some bacteria, viruses and other micro-organisms may become aggressive to the host in which they live and that others may become aggressive as a result of mutation through other species. This aggressiveness manifests itself through the diseases which afflict man and all that is living. The cause and nature of those diseases which have been most devastating for human society and which have greatly influenced the course of history are portrayed in this book, as are the means by which the spread of infections may be controlled before they progress to become epidemics and pandemics.
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Topic
MedicineSubtopic
Infectious DiseasesChapter 1
The Bacteria, Viruses and Other
Micro-Organisms with Which We Live
Micro-Organisms with Which We Live
In our introduction we stated that on and within our bodies, we have a vast number of microorganisms. These include the bacteria and the viruses which first the microscope and then the electron microscope had enabled us to visualize, and then, by using other technologies, to categorize these small structures into their different species and sub-species.
Apart from the difference in their size, the bacteria being many times larger than the virus, the most striking difference between the bacteria and the viruses is that whereas a virus must live within a living cell. (A virus may survive for a variable time outside a cell but must be intracellular in order to nourish itself and reproduce.) A bacteria may live on or in the body of its host but is also capable of free living.
As we have already related, since the middle of the nineteenth century it has been known that bacteria, viruses, and other microorganisms provoke disease. Why therefore, if our bodies are full of these structures, are we not in a constant state of illness?
Certainly, this question was frequently raised after it had been shown by Pasteur that bacteria cause disease. Perhaps understandably, a xenophobia directed against bacteria entered the human psyche in the same manner as the wrong doing by one member of a particular religious sect or racial group has been known to provoke violence against all members of the sect.
âWhy take chances,â says the mob, âeliminate them all.â And as history shows only too clearly, the wrong doing or even the misunderstanding of an individual, a group, a sect or a race may provoke aggression against the whole group.
After Pasteurâs discoveries, the chase of bacteria became the order of the day. The bowel, a structure normally full of bacteria and relatively accessible, became victim to the âcolonic washoutâ, a procedure which quite reasonably gave the client the belief that no bacteria could survive such an onslaught. Numerous are the testimonials to its efficacity and to the benefits which accrued.
In a manner perhaps less dramatic, it was not long before each attainable body part would be subject to a systematic âdisinfectionâ in the misguided believe that true sterility, the removal of all bacteria and other microorganisms was not only attainable but also to be desired.
Of course, shortly after these often unpleasant procedures had been completed and the bills of the operatives paid, the bacteria returned to the settlements from which they had been displaced with remarkable rapidity.
In fact, as we know now, this cohabitation; this living together of man with his community of viruses, bacteria and other microorganisms is, for the main part, advantageous for both parties. These organisms which live upon and within our bodies are now termed our âfloraâ, a term which has somewhat softened their image.
The term âfloraâ gives the image of a garden, and as every gardener knows, by choosing his plants and positioning them correctly, there remains little space for the undesirables; the weeds and aggressive plants which are all too ready to take advantage of a vacant spot.
As in a well-ordered garden, our correctly constituted âfloraâ leaves no room for the undesirable incomer and crowds out those âforeignâ bacteria, viruses, and other microorganisms who may attempt to gain a foothold.
But keeping others at bay is not the only roll of our âfloraâ. Certain bacteria which make up the âfloraâ in our gut, also play a role in the creation of an essential vitamin.
From studies which began in 1929, the Danish scientist Henrik Dam (1895â1976) deduced the presence of a vitamin which is essential for the process of coagulation. Coagulation is the mechanism which stops bleeding when we cut ourselves.
Dam published his findings in a German scientific journal. His âcoagulation vitaminâ was therefore written âKoagulation vitaminâ, the âKâ in the German spelling of coagulation becoming the identifying symbol of the new vitamin, Vitamin K.
For his work on Vitamin K, Henrik Dam received the Nobel prize for medicine in 1943.
Chapter 2
The Nature of An Infectious Disease
Having concluded that bacteria viruses, and other microorganisms are part of âourselvesâ; our âfloraâ, with which we coexist in a state of serenity and mutual self-help; we must now ask ourselves how this âGarden of Edenâ situation may change to become the nightmare of illness and death.
Firstly, we must ask the basic question: What is an infectious disease? To which the answer, in broad terms is always the same.
Simply stated, an infection is the invasion of the host organism (man, animal, or plant) by another living organism, to the almost certain benefit of the invader, and the unquestioned detriment of the host.
For most infections, and certainly those which have throughout history caused epidemics and pandemics, the infecting organism is a small and often unicellular microorganism. But let us remember that some invaders which can provoke disease may be quite large. Intestinal worms for example.
What is also a common characteristic of all infections is that each represents a form of parasitism, the infecting organism living off and nourishing itself from the person, animal, or plant which it has invaded. In addition, an infecting organism causes damage to the structures of that person, animal, or plant, sometimes to such an extent that it leads to their death.
It must of course be said that parasitism need not of itself be detrimental. Our own flora is an example of parasitism which cannot normally be seen as an infection â but read further!
How then, we may ask, did we move from a situation where man, woman, bacteria, viruses, and other microorganisms lived happily in the âGarden of Edenâ, to the plagues and pestilences which are the main reason for writing this book?
Certainly, we know from the earliest fossils that the âfallâ occurred long ago. Bacteria ravaged the dinosaurs as well as our earliest known ancestors.
If one follows the logic of Charles Darwin (1809â1882) and his theory of evolution which proposes that it was natural selection over many thousands of years which had determined the characteristics of the finches, tortoises, and mockingbirds which he studied in the Galapagos islands, then it is logical to consider that natural selection and evolution followed the same pattern for less exotic species such as bacteria, viruses, and other microorganisms.
As for the finches, tortoises, and mocking birds it is reasonable to offer the hypothesis that under threat for their survival, bacteria, viruses, and other microorganisms modified their structure and characteristics through natural selection, producing variants or mutants which improved the chance that their own species would survive.
As we shall see, these variants or mutants may turn out to be more or less aggressive towards man than the original form. A previously innocuous species perhaps producing variants or mutants with the capacity to cause serious disease and pandemics.
With reason, it is suggested that the coronavirus has evolved in this manner.
It is believed that the coronavirus has been with us for many millions of years. With the coming of the electron microscope in the 1930âs, the coronavirus was identified as the cause of infections which mainly affected poultry and pigs. In the mid 1960âs it was identified as one of the causes for coughs and colds in humans, infections which were, for the most part, benign in nature.
With the arrival of the variant SARS-CoV-2, the virus which causes COVID-19, the coronavirus achieved an exceptional degree of aggressivity towards man, and since that time the number of variants, each with a different degree of aggressivity has increased steadily.
The World Health Organization (WHO) now recommends the use of the letters of the Greek alphabet to identify the variants or mutants of SARS-CoV-2, the virus which causes COVID-19.
As of July 2021, four dominant variants or mutants of SARS-CoV-2 which have spread amongst the global population have been officially identified and recognized:
The Alpha Variant (formerly called the UK Variant and officially referred to as B.1.1.7), first found in London and Kent, the Beta Variant (formerly called the South Africa Variant and officially referred to as B.1.351), the Gamma Variant (formerly called the Brazil Variant and officially referred to as P.1), and the Delta Variant (formerly called the India Variant and officially referred to as B.1.617.2).
It is now considered most probable that SARS-CoV-2, the virus which causes COVID-19, the cause of the present pandemic, developed from a less aggressive coronavirus during its passage through one or perhaps several different animal species.
Passage of an infective agent such as a bacteria, virus, or other microorganism to a different animal species demands an adaption to the new environment, and adaptation to any new environment will inevitably lead to a process of natural selection. Those bacteria, viruses, or other microorganisms which adapt in the manner which is best suited to this new environment will be those which survive and reproduce.
Thus, as indicated by Darwin, when faced with a new environment, a different animal host for example, the virus, bacteria, or other microorganism will need to adapt and following adaptation, natural selection will choose the adaption which is most assists survival and reproduction.
If the habitat of man, animals, bacteria, viruses, and other microorganisms remains relatively constant, then little adaptation will be necessary.
If, however, climatic, or other changes eliminate some species of animal and bring in others, then passage through these new species will require adaption. Natural selection will then follow, producing variants or mutants of the original bacteria, virus, or other micro-organism which may be more, or sometimes less virulent to man than the original version.
It is reasonable to assume that with climate change, we shall be faced with the appearance of old and known bacteria, viruses, and microorganisms, which, like the coronavirus present with new characteristics following their adaptation. These new characteristics need not be unfavourable to man, but it is prudent to assume that any change may be to our disfavour.
When, in 1796, long before viruses had been identified, Edward Jenner (1749 â 1823) inoculated the arm of a young boy with the exudate from a cow-pox lesion present on the hand of a dairymaid, and two months later inoculated the same boy with material from a true case of smallpox; no illness resulted. The passage of the pox virus through the cow had resulted in a diminution of its virulence, yet it retained characteristics close to those of true smallpox; so much so that the effect produced in the body by the inoculation of cowpox (which we now know to be the production of antibodies) had protected the young boy, as it has protected the lives of many millions from the scourge of smallpox since that time.
Chapter 3
The...