Epidemiology and Biostatic Study

Introduction to Epidemiology

At the end of this lesson, students are able to:

1. State Father of Occupational Medicine, Father of Immunology, Father of Modern Epidemiology and Typhoid Mary

2. Define epidemiology 3. State the uses of epidemiology 4. Describe the natural history of disease

5. Illustrate the epidemiologic triangle

LESSON OUTLINE 1. History / evolution of epidemiology 2. Terminology in Epidemiology 3. Uses of epidemiology 4. Natural history of disease 5. Epidemiologic triangle

History / Evolution of Epidemiology

Bernardino Ramazzini (1633 - 1714) Italy 

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Father Of Occupational Medicine Occupational diseases “What is your occupation?”

Edward Jenner (1749 – 1823) England

 Father of Immunology  Pioneer of smallpox vaccine  “Saved more lives than the work of any other man"  In 1979, the World Health Organization declared smallpox an eradicated disease

John Snow (1813 – 1858) England  Father of Modern Epidemiology

 Mapping of cholera cases in East London during cholera epidemic in 1854  Traced source to a single well on Broad Street that had been contaminated by sewage

Dot / Spot Map

Source of outbreak

Mary Mallon (1869 – 1938) US

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Known as Typhoid Mary Asymptomatic / healthy carrier Cook Typhoid fever

Typhoid Mary  Mary Mallon, a cook responsible for 1904 typhoid fever epidemic  When source of disease was traced, Mary had disappeared only to resurface in 1907 when more cases occurred  Again Mary fled, but authorities led by George Soper, caught her and had her quarantined on North Brother Island  In 1910 the health department released her on condition that she never accept employment involving the handling of food  Four years later, Soper began looking for Mary again when two new epidemics broke out; Mary had worked as a cook at both places  She was found and returned to North Brother Island, where she remained the rest of her life until a paralytic stroke in 1932 led to her slow death, six years later

Statistics & Biostatistics Statistics – the science and art of dealing with variation of data in order to obtain reliable results and conclusions Biostatistics – the application of statistics to problems in the biological sciences, health and medicine Eg: • Computing age-adjusted cancer incidence rates to determine trends over time and locality • Calculating statistical measures of the risk of developing brain tumors following cell phone use • Quantifying the relationship between use of Cox-2 inhibitors and quality of life

Epidemiology Epidemiology is a word with Greek origins: epi, meaning “on, upon or befall,” demos, meaning “people,” and logos, meaning “the study of.”

The study of what is upon the people

Definition of Epidemiology The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems (WHO)

Distribution • the frequency and pattern of health events in a population. • Frequency refers to the number of health events

• Pattern refers to the occurrence of healthrelated events by time, place, and person. • Time patterns may be annual, seasonal, weekly, daily, hourly, that may influence health events occurrence. • Place patterns include geographic variation, urban/rural differences, and location of work sites or schools. • Personal characteristics include demographic factors such as age, sex, marital status, socioeconomic status, behaviors and environmental exposures.

Frequency & Pattern

Determinants • Are the causes and factors that influence the occurrence of health-related events. • Eg. Eating contaminated food causes diarrhea

Health-related events • Anything that affects the well-being of a population. • disease epidemic • endemic diseases • chronic diseases • occupational health & safety – injury, disease • environmental health – water supply, foods • behaviors – lack of exercise, unhealthy eating, smoking

1. To determine the etiological or causal factors of diseases 2. To determine the frequency and distribution of a disease in a community 3. To evaluate preventive, therapeutic and intervention activities 4. To develop public health policies and regulations

5. To solve epidemics/outbreaks. 6. To predict disease occurrence, impact and distribution in a community. 7. Surveillance for new disease and changes in old ones. 8. To plan current and future health care needs.

It is the description of the progression of a disease from the first sign or manifestation of the disease until recovery or death

Ending

Beginning

Incubation Period

It is important to know about the natural history of a disease to help prevent, treat and control a disease

The Triangle has three components: 

Agent, or microbe that causes the disease (the “what” of the Triangle)

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Host, or organism harbouring the disease or carrier (the “who” of the Triangle)

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Environment, or those external factors that cause or allow disease transmission (the “where” of the Triangle)

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It is the model of infectious disease causation.

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It has 3 components: an external agent, a susceptible host and environment that brings the agent and the host together.

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Disease has been classically described as the result of an epidemiologic triangle.

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Infectious diseases result from the interaction of agent, host, and environment

1. US Department of Health and Human Services, Center for Disease Control and Prevention, 2012. Principles of Epidemiology in Public Health Practice, 3rd Edition, Atlanta.

2. R. Bonita, R. Beaglehole and T. Kjellstrom, 2006. Basic Epidemiology, 2nd Edition, World Health Organization, Geneva. 3. Karuthan C. and Krishnakumari K., 2009. Biostatistics for the Health Sciences. Mc Graw Hill.