concepts of epidemiology

• epidemiology - derived from greek words epi (up, upon), demo (people), and logos (study)
• american society of epidemiology - science of knowledge of the natural history of disease
• frost (1931) - science of the mass-phenomenon of infectious diseases or as the natural history of infectious diseases
• macmahon - science of the distribution and determinants of disease frequency in man
• leavell and clark - field of science which is concerned with the various factors and conditions that determine the occurrence and distribution of health, disease, defect, etc
• stallybras (1931) - science of infective disease, their prime causes, propagation and prevention
• stallybras (1931) - science of infective disease, their prime causes, propagation and prevention
• lilienfield (1976) - study of the distribution or physiologic condition in human populations and the factors that influence this contribution
• components

  human population

  factors

  agent
• great plague/bubonic plague - europe and asia
• cholera - london as investigated by john snow
• typhoid fever - studied by william bud
• hippocrates - recognized the influence of environment and expressed his idea that disease may be connected with person's environment
• fracastorious (girolamo fracastoro) - italian doctor and poet, used epidemiologic method of reasoning expressed in his book (de res contagiosa) and stated that disease results from specific contagious or seeds of disease
• john graunt (1620-1674) - first to provide survival rate/mortality rate
• john graunt (1620-1674) - famous for his uses of statistics specifically his notes on high infant mortality rate and believed to have the first life table
• dr william farr (1807-1883) - noted for his work on statistics notably mortality among cornish metal workers, prisoners, etc
• from 1950's, epidemiology has been applied to chronic disease and other conditions (smoking and lung cancer)
• objectives of epidemiology

  identify etiology or the cause of disease

  determine extent of disease

  study natural history and prognosis of disease

  evaluate new preventive and therapeutic measures

  provide foundation for developing public policy and regulatory decision
• aims of epidemiology

  prevention of disease

  maintenance of health

  promotion of health
• human population - group of people within geographic location (sick or healthy)
• components (based in lilienfield definition)

  human population

  distribution

  factors
• geographic boundaries - towns, cities, etc
• characteristics or attributes - working populations, school children, healthy individuals, etc
• distribution - occurence of disease according to person, place and time
• epidemic - occurence in a community of cases in excess or normal expectancy (outbreak) such as sars outbreak in china
• endemic - constant or habitual presence of a disease/agent in a given place (schistosomiasis in paolo, leyte and malaria in Palawan)
• pandemic - epidemic of worldwide proportion (hiv-aids, sars)
• sporadic - dew, unrelated cases in several areas; happens occasionally
• factors - all that affects the causation and distribution of the diseases
• host - result of interactions of genetic endowment
• agent - properties of this are important in disease occurence
• morphology - size, shape, and structure
• chemical composition - rna and/or dna, lipoprotein
• antigenic properties - basis for specificity
• viability - spores in bacillus anthracis
• host range - infecting all animals
• properties which relate to its perpetuation as species

  viability

  growth requirements

  host range

  vulnerability to chemotherapy

  evolution of drug resistant strains

  changes in antigenic character
• infectivity - infectiousness, ability to infect
• pathogenicity - ability to cause disease, depends on rapidity and extent