Epidemiology

• Epidemiology


  The study of determinants, distribution, and frequency of disease (who gets the disease and why)

  
• Epidemiology


  The study of the distribution and determinants of health-related states or events in specified populations, and the specification of this study to control of health problems

  
• Epidemiology


  Study the occurrence and distribution of diseases as well as distribution of determinants of health state and events in specified population

  
• Epidemiology


  The application of this study to control health problems
• Epidemiology


  Field of science dealing with the relationship of the various factors which determine the frequencies and distribution of an infectious process
• Two broad types of epidemiology

  • Descriptive Epidemiology
  • Analytical Epidemiology

  
• Descriptive Epidemiology


  Examining the distribution of disease in a population, and observing the basic features of its distribution (Person, Place, Time)

  
• Analytical Epidemiology


  Investigating a hypothesis about the disease by studying how exposure relate to disease. (Know where to look, know what to control for, develop viable hypotheses)
• Terminologies


  • Epidemic
  • Endemic disease
  • Epidemiologist
  • Pandemic
  • Infection
  • Contamination
  • Infestation
  • Infectious Disease
  • Frequency
  • Pattern
  • Risk factors

  
• Uses of epidemiology


  • To determine, describe, and report on the natural course of disease, disability, injury and death
  • To aid in the planning and development of health services and programs
  • To provide administrative and planning data
  • To study the cause of disease, or conditions, disorders, disabilities, etc.
  • To determine the primary agent responsible or ascertain causative factors
  • To determine the characteristics of the agent or causative factors
  • To determine the mode of transmission
  • To determine contributing factors
  • To identify and determine geographic patterns

  
• Purpose of epidemiology


  • To provide a basis for developing disease control and prevention measures for groups at risk
• Person factors


  • Age
  • Gender
  • Ethnic group
  • Genetic predisposition
  • Concurrent disease
  • Diet
  • Physical activity
  • Smoking
  • Risk taking behavior
  • SES
  • Education
  • Occupation
• Geographic place factors


  • Presence of agents or vectors
  • Climate
  • Geology
  • Population density
  • Economic development
  • Nutritional practices
  • Medical practices
• Time factors


  • Calendar time
  • Time since an event
  • Physiologic cycles
  • Age (time since birth)
  • Seasonality
  • Temporal trends
• Three major aims of epidemiology


  • Construct or complete the natural history of disease so that adequate measures for diagnosis and treatment, and prevention can be formulated
  • To study immediate and special problems in the field of health. The study could provide the necessary data upon which program may be based; to guide the program, assessing its progress and pinpointing failures, etc.
  • To evaluate the effectiveness of therapy, preventive measures and programmes
• Primary care physician


  Is concerned with the health of the individual
• Epidemiologist


  Is concerned with the health of the population, monitoring health at a population level is important to determine when unexpected or unacceptable levels of health events occur such as illness, injury or death
• Epidemiologist


  Want to know what it is that the sick people have in common, for this reason the epidemiology is sometimes referred to population medicine
• Epidemiologist


  Study the behavior of disease in the community rather than in individual patients and includes the study of reservoirs and sources of human disease
• Epidemiologist


  Studies the patterns of disease occurrence in human populations and the factors that influence this pattern

  
• Epidemic


  An increase in the frequency (incidence) of a disease above the usual and expected rate, which is called the endemic rate

  
• Epidemiology count cases of a disease, and when they detect the sign of epidemic, they ask who, when and where questions
• Notifiable disease


  Surveillance made by the government before many people start dying. The timely reporting of cases of notifiable disease allows public health authorities to detect an emerging epidemic at an early stage
• A typical epidemiologic investigation of an outbreak of hepatitis involves identifying the who, where and when
• Goal of epidemiology


  The ultimate goal is to use this knowledge to control and prevent the spread of disease
• John Snow


  Father of modern epidemiology
• Two main areas of investigation in epidemiology


  • Describes the distribution of health status in terms of age, gender, race, geography, and time
  • Patterns of disease distribution in terms of causal factor

  
• Epidemiology of any disease or event


  Studies the factor which contribute to its causation and behavior- AGENT, HOST, ENVIRONMENT

  
• Epidemiology concept maintains that there can be no single cause of disease
• Types of agents


  • Living or non-living things, physical or mechanical in nature such as extremes of temperature, light electricity
  • Chemicals- endogenous (within the body) or exogenous (poison)
• Characteristics of agent of disease


  • Inherent characteristics- physical feature, biological requirement, chemical composition, resistance
  • Characteristic in relation to the environment- refers to the reservoir and source of infection and modes of transmission
  • Characteristic directly related to man- Infectivity, Pathogenicity, Virulence, Antigenicity
• Types of carriers


  • Active carrier
  • Convalescent carrier
  • Healthy carrier
  • Incubatory carrier
  • Intermittent carrier
• Modes of transmission


  • Direct transmission
  • Indirect transmission- Vehicle borne, Vector-borne (Mechanical vector, Biological vector)
  • Airborne- Droplet nuclei, Dust
• Host factors of disease

  • Age
  • Sex
  • Race
  • Habits, customs and religions
  • Exposure to agent
• Communicable disease


  An illness caused by some specific biological agent or its toxic product that can be transmitted from an infected person, animal or inanimate reservoir to a susceptible host
• Non-communicable disease


  A disease that cannot be transmitted from infected host to susceptible host
• Biological agents


  • Viruses
  • Rickettsia
  • Bacteria
  • Fungi
  • Protozoa
  • Metazoa
• Chemical agents


  • Pesticides
  • Food additives
  • Air pollutants
  • Cigarette smoke
• Physical agents


  • Heat
  • Light
  • Radiation
  • Noise
  • Vibration
  • Speeding objects
• Humoral defense


  Cells in our body like plasma cells and lymphocytes that produce antibodies to neutralize harmful effects of the infectious agents and body fluids in our body that possess substance that have antimicrobial properties