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In this unusual case, two young army trainees who were both seemingly in good health, contracted a form of meningitis Streptococcus pneumonia meningitis and died. They belonged to the same company and instances of pneumonia were high in their squad mates. They looked not only at the circumstances surrounding the deaths of the two individuals, but cases where trainees excused from training due to sickness.

They examined a number of other factors too and devised a solution that greatly reduced the risk of meningitis occurring at this camp and other military facilities. They gave advice on cleanliness, procedures for sickness and prescribed antibiotics to those affected.

Validity and Bias in Epidemiology

This study demonstrates that epidemiology underpins public health policy both in terms of preventive planning and in control This was not an only case and recent studies of the spread of Ebola in Africa in and Zika in South America in have demonstrated further precisely why the study of instances of diseases, illness and other conditions is just as important as treatment.

Although epidemiology is a largely modern science, it's actual history goes back centuries to way before the Enlightenment and the scientific method. Even as far back as classical Greece, great thinkers attempted to come up with naturalistic suggestions for the causes of illness rather than supernatural causes. Hippocrates was the first to push this idea in an essay called On Airs, Waters, and Places Before, during and after the Classical Greek period, the general perception was that sin, mischievous spirits, demonic possession, bad air and the will of the gods or God in the case of early Christian communities later on all caused disease and sickness.

However, without a rigorous testing method, much of the prevailing theory on the spread of illness and disease was stuck in the past for centuries to come. The prevailing theory behind the rise of The Black Death in s was miasma theory bad air spread by pollution or rotting food The idea did take on some of Hippocrates theory in that it suggested there was an environmental cause - and there is for some conditions, although not in the way was generally believed at the time.

Much of medieval Europe still held on to ancient supernatural notions that demonic possession, sin and bad air caused disease. Miasma theory did not die out as a concept until the 19 th century 13 , surprisingly late considering the great age of science that was already dawning. It remained the major belief behind the spread of disease, but even before the Age of Enlightenment and the birth of modern science, it had its critics and those willing to challenge the orthodoxy.

Around the middle of the 16 th century, Girolamo Fracastoro first suggested that tiny living particles too small for people to see may have caused some diseases His hypothesis flew in the face of received wisdom of miasma theory and it would be another years before the invention of the microscope that would prove him right. He was also the first to suggest that populations could prevent the spread of disease through personal hygiene.

Despite having little evidence to back up his hypothesis, his ideas were not completely fanciful. He observed and noted several cases where disease instances had greatly reduced or eliminated with the use of fire burning bodies, using fire barriers. John Graunt is one of the most prominent early modern epidemiologists, and he never intended it to be that way. A haberdasher by trade, he found a love of statistics and probability from a young age.

He published the first study on what today we could call the science of demographics 15 and he used this to calculate probable survival rates of plague patients probably Bubonic Plague during the reign of Charles II. He also invented the life table, a system still used in a range of sciences today but particularly in those who study instances of disease.

Further, he found strong correlations between decreased mortality and disease, showing that in times of plague, young and healty people were just as likely to die as the old and infirm. Epidemiology had another boost in the early 19 th century when William Farr invented the modern system of medical statistics, building on the work of John Graunt. Although his belief in what are now obsolete approaches to medical science, his work in collecting data on death demographics 16 related to age, social status and other social factors allowed his peers to begin to realize that some diseases have social patterns.

He worked with but fundamentally disagreed with fellow early epidemiologist John Snow who theorized that water was a major cause of the London cholera epidemic. This hypothesis would later prove true and following Snow's death, Farr would come to accept the changing face of the modern science.

Perhaps by accident, miasma theory drove the human race towards a more scientific and less supernaturalistic understanding of the causes of disease later in the 19 th century. It was understandable in terms of the evidence as it stood, but today we realize that correlation does not mean causation 6 - and bad smells sometimes correlate with disease, especially when poor sanitation is the root cause of the spread of the disease.

Areas of Study within Epidemiology

A government session at the Houses of Parliament was abandoned due to an awful smell coming from the River Thames and the pipes that fed into it. This was in the middle of the city's and possibly the world's at the time largest ever cholera epidemic. As a result, the British government voted to modernize the sanitation, housing and street cleanliness, replacing all the old pipes, increasing the size of the network and reducing the strain, and removing the smell from the city that had blighted it.

The cholera epidemic came to an end shortly afterwards. Although it was a massive improvement to public health, the perception of the cause remained in error. People still believed that bad smells caused sickness, rather than that excess dirt and poor sanitation caused sickness that would also create the bad smells and the environment for disease to breed and spread Despite this error in thinking, there were proponents of the idea of a waterborne cause of the cholera epidemic and the rise of the science of bacteriology in the later 19 th century would shape the 20 th century Louis Pasteur's work in developing vaccine theory and pasteurization for food represented a giant leap forward.

Together with the work of Edward Jenner who developed the world's first vaccine for smallpox , and effectively create the medical science of immunology, epidemiology would see great strides but also face new challenges in the 20 th century. The 20 th century saw several immense shifts in thinking and science within the discipline of epidemiology, largely thanks to the work of forbearers in late 19 th century.

Bacteriology was now a firmly established medical scientific concept, and so was immunology.

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The role of bacteria in the causes of some diseases was only gaining more and more evidence and the growing disciple of virology was equally gaining ground. The 20 th century was notable for two world wars but also for medical science and pandemic. Spanish Flu was the biggest disease of the century, killing more people in than the war that had just ended.

The science was already making great strides in the early 20 th century. Janet Lane-Claypon examined breast cancer survivors, comparing them to women of a similar demographic who did not have breast cancer and had never developed it.


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In this, she designed the first case control study Around the same time, her contemporary Sir Ronald Ross received the Nobel Prize for Physiology when he discovered that mosquitoes transmitted the parasite that led to malaria. His discovery, in turn, led to the first treatments of the condition Diseases that were common in the western world in the 20 th century are now rare or extinct. A major diphtheria epidemic in the USA circa saw the first tests and licensing of vaccination against the disease In the 21 st century, this condition is rare.

EPIDEMIOLOGY - GLOSSARY OF EPIDEMIOLOGICAL AND STATISTICAL TERMINOLOGY

The same can be said for polio, which peaked between and globally. It is no coincidence that the first vaccines against this disease in saw a massive drop of infection in the western world.


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Qualitative studies conducted after a quantitative survey can provide key insights for interpretation of results. It is the position of this paper, in regard to field epidemiology, that both qualitative and quantitative investigation are required for a full understanding of disease ecology.

Principles of Rapid Appraisal Methods Rapid and participatory appraisals are based on two important principles which are designed to improve the quality and reliability of the information gained. Having noted the way in which PRA techniques are, in themselves, a means of improving information quality, it should also be said that they are useful tools for investigating linkages within farming systems and determining causality.

PRAs are often useful as a follow-up mechanism to investigate, for example, the findings of a more formal study.

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Data Sources in Rapid Appraisals In applying the principles of flexibility and triangulation, a number of data sources must be tapped. These may be classified either as primary or secondary, depending on their closeness to the actual subjects of study.

Validity and bias in epidemiological research - Oxford Medicine

Sources within the communities studied would be seen as primary; all other sources would be secondary. Also included are the outcomes of participatory activities undertaken to study and evaluate local animal health problems. It is usual to consult as many secondary data sources as possible before undertaking field work; the results of this study may highlight issues to be given priority attention in the field study.

Factors which may militate against the use of Random Sampling While formal randomised studies and PRA work are often seen as complementary, it is sometimes not possible to carry out a formal study. This would make access difficult, and the drawing-up of an appropriate sampling frame difficult, if not impossible. A cheaper option and one which would solve the problem would be to use a rapid appraisal. Random surveys are designed around a particular need, they are large-scale, and require a large number of field staff.

These staff need not be of a particularly high level of training, but should understand the questionnaire they are using and be able to take appropriate samples if required. Appraisals, on the other hand, require a single small but specialised team to carry out an in-depth study of a number of factors playing a role in a given farming system. Overall, the costs of PRAs are thus much lower. Potential Sources of bias in Participatory Appraisals All epidemiological studies, even those that are randomised, need to be designed so as to minimise bias. Planning of PRA work is of great importance, as the sample is purposively selected..

While it is true that appraisals can often yield a depth of information not possible with formal surveys, they are not planned on the basis of a sampling frame with randomisation of survey localities.


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This means that survey planners need to be aware of possible biases and must consciously take steps to avoid them. Thus, it is essential to include the rural poor as key informants and insure they are interviewed in settings were they feel comfortable enough to express their views. PRA offers specific tools, such as wealth ranking, to help define the social strata within a community as well as each groups needs, views and interactions. This is one reason why it is important to seek training or assistance experienced in the application of PRA methods at the outset of any new program.

Advantages of Participatory Methods in Epidemiological Studies Despite possible pitfalls and the need for experience, there are a number of distinct advantages to the use of participatory methods.