Disease

Epidemiology

The study of diseases in human communities is called epidemiology. Epidemiologists investigate the biological, social, historical, or geographical relationships between a disease and its consequences. In any epidemiological study, the focus is on mortality (death) and morbidity (disease and/or illness) and the causal links between the two. The goal of epidemiology is twofold: to understand why morbidity or mortality rates may rise or fall; and to try to understand how and why a disease may wane and how to control future spread. The factors leading to increased morbidity and mortality rates may be biophysical, social, or environmental. Epidemiologists examine different diseases in their biological, social, or environmental contexts to determine how to reduce the spread and effects of particular diseases. Moreover, epidemiologists seek to identify new illnesses and place them into disease categories.

Many diseases fit into two broad categories: chronic or acute. Chronic diseases (or illnesses) are long-term conditions that may or may not require medical intervention, such as heart disease or high cholesterol. Acute diseases (or illnesses) are intense, short-term conditions, such as influenza or strep throat. Some chronic diseases are differentially intense, causing periods of decreased mobility or feelings of ill health. Depending on the person and their current state of health and the broader circumstances, both chronic and acute diseases can be the cause of mortality. Some diseases are also considered infectious, spreading from one person or animal to another person or animal, or even through one animal or insect to another animal or insect, and then to a human. Often, epidemiologists are interested in understanding the vector of an infectious disease, the subject through whom a disease passes as it spreads. Some infectious diseases can be carried from an insect to a human (such as malaria), while others are purely humanto-human (such as HIV).

When studying the spread of diseases, it is important to examine a multitude of factors, including the overall population that is impacted by a particular disease, the environmental context (broadly conceived) in which that disease is spreading, and the individual or community-based behaviors or practices that might intensify or mitigate the diffusion of a particular disease. It is impossible to partition one of these areas out from the rest, and so social scientists must consider the interrelationships among the multitude of factors that intensify certain disease distributions and limit others. Moreover, it is critical that those studying diseases take into consideration the broader socio-cultural and politicaleconomic contexts that play a crucial role in determining how certain diseases spread and why others may be stopped. As an example, malaria eradication programs have been very effective in a number of highly industrialized economies, while this particular disease, spread via mosquitoes, remains a leading killer of people in many parts of the developing world. There is thus a geography that underlies any disease distribution or pattern, a geography based in the context of human–environmental and social relationships.

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