Epidemiology is defined as the study of patterns of health and illness including the associated factors at the population level. It involves the study of the distribution and determinants of health, disease and injuries in human populations thus implying that diseases are not randomly distributed but that subgroups vary in the frequency of the many different diseases. Epidemiology is one of the major methods used in public health research, which aids to inform evidence-based medicine that is used in identifying risk factors for disease and also determines the optimal treatment approaches to clinical practice .Epidemiology relies on many other scientific disciplines like biology, biostatistics and social science disciplines. Earlier on it was restricted to infectious diseases only but nowadays it is applied to many chronic conditions like injuries, drug addiction, adverse drug reactions mental illnesses, congenital defects and health services research. Some of the major fundamental concepts in epidemiology are; Multiple Causation of Disease and the Epidemiologic Triangle, Natural History of Disease, Variations in Severity of Illness, Reservoirs and Mechanism of Transmission.
Define and explain epidemiologic transition and describe the factors involved in epidemiologic transition
Epidemiological transition is a phase of development that is witnessed by an abrupt and severe increase in the population's growth rate. It is said to be the general shift from acute deficiency and infectious diseases that are characteristic of underdevelopment to diseases that are chronic and non communicable which is a characteristic of advanced levels of development and modernization. This is as a result of medical improvement in disease or sickness therapy and treatment, which is followed by a re-leveling of population growth from ensuing decline in fertility rates. The indicators that are most evident in this transition are the various changes in the patterns of mortality, that are particularly related to the cause of death and the changes in morbidity. (Wahdan, 1996)
Epidemiological transition was though to be a unidirectional process, but over time it became evident that it is more complex and dynamic. This was mainly because the disease and health pattern of any society normally evolves in varied number of ways as a result of socioeconomic, demographic, technological, cultural environmental and biological changes. It is viewed as a transformational process that is continuous whereby there are some diseases that are disappearing while others are re-emerging.
There are several factors involved in the epidemiological transition. Some of the most important include:
Demographic changes play a very important part in changes to both mortality and fertility. It is normally seen that as populations become healthier, there tends to be a reduction in mortality especially in infants and children and this is followed by reduction in fertility rates. As a result more people will survive to adulthood and hence have the disease patterns of adults. Most of these diseases are non-communicable. This increases the number of cases of deaths from such diseases as a result of this demographic change.
Microorganisms are seen to constantly undergo changes which enable them to handle the ever increasingly hostile environment. It is known that the development of mechanisms that would enable survival of microorganisms that are most adaptable is much more rapid than the development of the defense mechanisms which would allow their hosts to fight microbial invaders. This process of adaptation involves finding the weaknesses in the hosts and exploiting them. This can happen by means of alteration in antigenic identity, emergence of drug-resistant strains or dual infection. (Wahdan, 1996)
Existing evidence show that certain changes in disease patterns .An example is the reduction in the occurrence of communicable diseases like cholera, are usually caused by improvement in environmental sanitation. This is also the case when environmental factors at times facilitate the infection of some diseases especially by promoting breeding of vectors of diseases.
Social, cultural and behavioral factors
Social, cultural and behavioral factors have close relations. An example is when a society changes from being agricultural to an industrial society, the peoples health may be affected.
Say we suspect a relationship between a specific dietary factor and heart disease. Can you think of ways of epidemiologically assessing whether indeed the dietary factor is a determinant of heart disease?
In order to epidemiologically asses if the dietary factor is a determinant of heart disease first it is important to check if there is any possibility of multiple causation of this disease. This is whereby one determines if there may be any other causes of this heart disease so as to determine if the dietary factor is an agent of this disease.
After this the Natural history of the heart should be determined through its stage of susceptibility whereby the disease is yet to develop and check if the presence of the dietary factor favors its occurrence. Then the stage of Pre-symptomatic Disease where the disease process begins then the Stage of Clinical Disease where there are recognizable signs of the disease before assessing the stage of disability of the heart disease.
After this the levels of prevention of the disease from occurring by seeing if the people who are not exposed to a certain type of diet are least likely to get the heart disease or not. From this it is also determined if the disease is more severe in patients taking a certain diet.
Which types of diseases do you think pose a greater risk for the population of the United States: infectious diseases or chronic diseases? Please explain
In the United States the population is at a greater risk of chronic diseases as compared to infectious diseases. This is largely because of the epidemiological transition that is as a result of a number of factors some of these factors include;
In the United States the health facilities and system have been improving more and more over time and as a result the population in general has grown healthier. This has resulted in reduction in mortality of the children and orphans and reduced fertility rates. Therefore many people are older and hence much more likely to get chronic diseases compared to infectious diseases.
In the United States the matters of environment such as sanitation are properly maintained .as a result of this infectious diseases are not likely to affect compared to chronic diseases.
Social, cultural and behavioral factors
These factors have proven to play a very important part in the lives of the United States population. A good example is the cases of lifestyle. The changes in lifestyles in the United States do not in any way facilitate the spread of infectious diseases but rather the non infectious and chronic diseases.