Epidemiology - How Diseases Spread

The branch of medicine which deals with the incidence, distribution, and possible control of diseases and other factors relating to health.

Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in defined populations.


It is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences. 


Major areas of epidemiological study include disease causation, transmission, outbreak investigation, disease surveillance, environmental epidemiology, forensic epidemiology, occupational epidemiology, screening, biomonitoring, and comparisons of treatment effects such as in clinical trials. Epidemiologists rely on other scientific disciplines like biology to better understand disease processes, statistics to make efficient use of the data and draw appropriate conclusions, social sciences to better understand proximate and distal causes, and engineering for exposure assessment.


Epidemiology, literally meaning "the study of what is upon the people", is derived from Greek epi 'upon, among', demos  'people, district', and logos 'study, word, discourse', suggesting that it applies only to human populations. However, the term is widely used in studies of zoological populations (veterinary epidemiology), although the term "epizoology" is available, and it has also been applied to studies of plant populations (botanical or plant disease epidemiology). 


The distinction between "epidemic" and "endemic" was first drawn by Hippocrates, to distinguish between diseases that are "visited upon" a population (epidemic) from those that "reside within" a population (endemic).  The term "epidemiology" appears to have first been used to describe the study of epidemics in 1802 by the Spanish physician Villalba in Epidemiología Española.  Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic.


The term epidemiology is now widely applied to cover the description and causation of not only epidemic, infectious disease, but of disease in general, including related conditions. Some examples of topics examined through epidemiology include as high blood pressure, mental illness and obesity. Therefore, this epidemiology is based upon how the pattern of the disease causes change in the function of human beings.


https://en.wikipedia.org/wiki/Epidemiology


Epidemiology is the study of how often diseases occur in different groups of people and why. Epidemiological information is used to plan and evaluate strategies to prevent illness and as a guide to the management of patients in whom disease has already developed.


Like the clinical findings and pathology, the epidemiology of a disease is an integral part of its basic description. The subject has its special techniques of data collection and interpretation, and its necessary jargon for technical terms. This short book aims to provide an ABC of the epidemiological approach, its terminology, and its methods. Our only assumption will be that readers already believe that epidemiological questions are worth answering. This introduction will indicate some of the distinctive characteristics of the epidemiological approach.


Epidemiology for the Uninitiated

Chapters


https://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated/1-what-epidemiology









Principles of Epidemiology, 3rd Edition


Epidemiology is the method used to find the causes of health outcomes and diseases in populations. In epidemiology, the patient is the community and individuals are viewed collectively. By definition, epidemiology is the study (scientific, systematic, and data-driven) of the distribution (frequency, pattern) and determinants (causes, risk factors) of health-related states and events (not just diseases) in specified populations (neighborhood, school, city, state, country, global). It is also the application of this study to the control of health problems (Source: Principles of Epidemiology, 3rd Edition).



What public health problems or events are investigated?
Environmental exposures
  • Lead and heavy metals
  • Air pollutants and other asthma triggers
Infectious diseases
  • Foodborne illness
  • Influenza and pneumonia
Injuries
  • Increased homicides in a community
  • National surge in domestic violence
Non-infectious diseases
  • Localized or widespread rise in a particular type of cancer
  • Increase in a major birth defect
Natural disasters
  • Hurricanes Katrina and Rita (2005)
  • Haiti earthquake (2010)
Terrorism
  • World Trade Center (2001)
  • Anthrax release (2001)

 


Introduction

This course [book] was developed by the Centers for Disease Control and Prevention (CDC) as a self-study course. Continuing Education for this course is no longer available.

Objectives

Students who successfully complete this course should be able to correctly:

  • Describe key features and applications of descriptive and analytic epidemiology.
  • Calculate and interpret ratios, proportions, incidence rates, mortality rates, prevalence, and years of potential life lost.
  • Calculate and interpret mean, median, mode, ranges, variance, standard deviation, and confidence interval.
  • Prepare and apply tables, graphs, and charts such as arithmetic-scale line, scatter diagram, pie chart, and box plot.
  • Describe the processes, uses, and evaluation of public health surveillance.
  • Describe the steps of an outbreak investigation.

Course Design

This course covers basic epidemiology principles, concepts, and procedures useful in the surveillance and investigation of health-related states or events. It is designed for federal, state, and local government health professionals and private sector health professionals who are responsible for disease surveillance or investigation. A basic understanding of the practices of public health and biostatistics is recommended.

Course Materials

The course materials consist of six lessons. Each lesson presents instructional text interspersed with relevant exercises that apply and test knowledge and skills gained.

Lesson One: Introduction to Epidemiology

Key features and applications of descriptive and analytic epidemiology

Lesson Two: Summarizing Data

Calculation and interpretation of mean, median, mode, ranges, variance, standard deviation, and confidence interval

Lesson Three: Measures of Risk

Calculation and interpretation of ratios, proportions, incidence rates, mortality rates, prevalence, and years of potential life lost

Lesson Four: Displaying Public Health Data

Preparation and application of tables, graphs, and charts such as arithmetic-scale line, histograms, pie chart, and box plot

Lesson Five: Public Health Surveillance

Processes, uses, and evaluation of public health surveillance in the United States

Lesson Six: Investigating an Outbreak

Steps of an outbreak investigation

Glossary

A Glossary that defines the major terms used in the course is also provided at the end of Lesson Six.

More on how to use this textbook


Epidemiology of COVID-19


Epidemiology - Latest Research and News | Nature

https://www.nature.com/subjects/epidemiology


COVID-19: Epidemiology, virology, and prevention 

https://www.uptodate.com/contents/covid-19-epidemiology-virology-and-prevention


About COVID-19 Epidemiology Investigating COVID-19: 

The Science Behind CDC’s Response 

https://www.cdc.gov/coronavirus/2019-ncov/science/about-epidemiology/index.html


Epidemiology of COVID-19 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7364648/

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