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The Role of Public Health and Healthcare Organizations in

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					Introduction to Public Health and
Epidemiology


   HCA 202
   Chris Cochran, Ph.D.
   August 29, 2005
Brief History of Public Health: Greco-
Roman Period

   Hippocrates: “Whoever wishes to pursue
    properly the science of medicine … ought to
    consider the effects of the season of the year,
    the hot winds and the cold, the properties of
    the waters, the setting of the town, the
    behavior of the people
   Romans build aqueducts to bring water from
    distant sources and to remove sewage
Brief History of Public Health:
The Middle Ages
     Public health declines
     Disease and lack of sanitation rampant
     Increase in trade between cities also enabled
      the spread of disease
     Bubonic plague hits Europe between 1349-
      1354 killing one-third of the population
     By the end of the middle ages, healthcare
      starts to redevelop; rudimentary food-safety
      guidelines are introduced
Brief History of Public Health:
The Renaissance

  Lost knowledge reemerges
   First systematic classification of
    diseases undertaken.
   Occupational related disease is first
    identified by Paracelsus. This knowledge
    is still used today.
History of Public Health:
The Enlightenment

   First surveys seeking information related
    to diseases and health are developed
   Edward Jenner observed that milkmaids
    who had cowpox did not contract
    smallpox
   Industrial revolution improves sanitation
    but creates new environmental hazards
    of water and air
Brief History of Public Health:
The Sanitary Movement
     Regular bathing, clean water and controlled waste disposal is
      promoted
     To control fires, New York constructs one of the first municipal
      water systems
     River and Harbor Act of 1899, implemented by federal
      government to protect waterways from dumping of debris
      becomes the basis for protection from pollutants
     Pasteur and Koch develop germ theory of disease
     John Snow initiates the study of Epidemiology
     Science and engineering expands at rapid pace furthering the
      advance of medicine
     Use of antiseptics in hospitals allows them to become places
      where the sick can be treated, not places to die
Brief History of Public Health:
The Age of Bacteria
   Connection made between bacteria and viruses and
    disease
   Pasteurization U.S. adopts the Pure Food and Drug
    Act
   Important species of bacteria are isolated and
    identified including Escherichia coli and
    staphylococcus
   Identification of vectors helps battle communicable
    disease.
   Elements of the immune system are identified creating
    regional laboratories devoted to disease research
   Drinking water and sewage treatment plants causes a
    decline in typhoid
Brief History of Public Health:
Modern Times
     WWI introduced poison gas as warfare
     Draining of swamps reduces mosquito borne disease
     In 1919, “Spanish Flu” pandemic killed 30 million world-wide
     Fleming discovers penicillin in 1928
     In WWII, protecting soldiers from disease leads to more death
      from injuries and wounds than from infection for the first time in
      history of wars
     The World Health Organization was formed in 1948
     Salk invents the polio vaccine
     In 1978, smallpox is eradicated from the planet
     In 1979, the first cases of AIDS appear
     In 1980s, poison gas once again used in warfare (Iran-Iraq war)
     New diseases emerge: AIDS, SARS, drug-resistant
      staphylococcus
Public Health:
Priorities for the Future
  Continue the pursuit of the eradication of
   disease and its causes
  Getting the public to understand that
   preventing disease does not rely solely
   on new medicine or inventions
  Making sure that we don’t undo the
   advances that we have already made
What is Health
    A state of complete physical, mental and social
     well-being, not merely the absence of disease or
     infirmity (WHO).
    Preventing premature death and preventing
     disability, preserving a physical environment that
     supports human life, cultivating family and
     community support, enhancing each individual’s
     inherent abilities to respond to and to act, and
     assuring that all Americans achieve and maintain
     a maximum level of functioning. (Healthy People
     2010)
Epidemiology Defined for Course

    THE STUDY OF THE DISTRIBUTION AND
     DETERMINANTS OF DISEASES AND
     INJURIES IN HUMAN POPULATIONS
        Concerned with frequencies and types of illnesses
         and injuries in groups of people & factors that
         influence their distribution
        Implies that disease is not randomly distributed
        Speculates that a chain of events must occur for
         illness or disability to take place
Epidemiology

  Endemic – habitual presence of a
   disease for a population within a given
   geographic area expectations
  Epidemic – occurrence of a group of
   illnesses within a given geographic area
   in excess of normal expectations
  Pandemic – world-wide or broad
   epidemic beyond many geographic
   regions
Objectives of Epidemiology
    Identify the etiology or cause of disease and
     risk factors
    Determine the extent of the disease in the
     community
    To study the natural history and prognosis of
     the disease
    To evaluate existing and new preventive
     measures and therapeutic measures and
     modes for health care delivery
    To help make public policy
The Relationship of Epidemiology to
Health Care Managers
    Understanding the increase/decrease in size of
     service populations
    To understand the characteristics and health status of
     the population for planning purposes
    To understand the consequences of health care
     problems
    To mesh the service organizations to the needs of the
     population
    To monitor performance by the organizations
    To modify the structure and processes and respond to
     environmental change
    To better formulate and evaluate public policy
Life Expectancy at Birth
Life Expectancy at Birth and at age 65 years 1900, 1950, and 2000
THE EPIDEMIOLOGICAL TRIAD



            HOST




            VECTOR


    AGENT            ENVIRONMENT
Classification for Health Status
Today
     Disease – a state of dysfunction of the normal
      physiological processes manifested as signs,
      symptoms, and abnormal physical or social function
      (includes injury).

     Functional Ability – a process used to represent how
      independently an individual can perform or fulfill
      expected social roles (physical and mental).

     Quality of Life – multidimensional concepts of
      measures covering symptoms/problem complexes,
      mobility, physical activity, emotional well-being and
      social functioning.
Blum’s Model of Factors Affecting
            Health

                          Health


Environment       Lifestyle    Biology   Medical Care
•Fetal            •Attitudes             •Prevention
•Physical         •Behavior              •Cure
•Socio/Cultural                          •Care
                                         •Rehabilitative
Prevention and Health Promotion

  Primary – inhibition of the development
   of the disease before it occurs
  Secondary – early detection and
   treatment of a disease
  Tertiary – the rehabilitation or restoration
   of effective functioning
Primary Cause of Death 1900
Primary Cause of Death 1997
Source: Healthy People 2010
Descriptive Epidemiology: Person,
Place and Time
  Person   Measures
    Age
    Sex
    Ethnic group and race
    Social class/social-economic
     status
Place Measures

    Place – related by natural barriers or by
     political boundaries.
        Natural boundaries – characterized by particular
         environmental or climatic condition (temperature,
         humidity, rainfall, altitude, mineral content, etc.).
        Place diseases – parasitic diseases that may be
         due to certain factors such as tropics, temperate, or
         other conditions.
        Political subdivisions – vary from entire nations to
         counties, cities, towns, and boroughs
Time and Place
    Time – basic aspect of epidemiology
        Secular trends (long-term variations, which occur
         over periods of time including years and decades).
         Good for studying "birth cohorts".
        Cyclic change – recurrent alteration in the
         frequency of disease (seasonal changes, for
         example – influenza)
    Clusters in time and place – difficult to
     determine the significance of linkages because
     there is no defined denominator
Using Rates In Epidemiology

  Numerator - the number of people/cases
   with the disease
  Denominator - (the population at risk)
Basic Descriptive Rates
  Rate - Number of events, cases, or
   deaths in a time period/Population in
   same area
  Ratio – Expresses the relationship
   between 2 numbers in the form of x:y or
   (x/y)k.
  Proportion – Specific type of ratio with
   the resultant value expressed as a
   percent.
DEATH RATES
    Three essential components of death
     rates:
      A population group exposed to the risk of
       death
      A time period

      The number of deaths occurring in the
       population during that time period (NOTE:
       best to take the population for the mid-point
       of the period being studied.
Types of Rates
    Crude Death Rate: Total # deaths from all causes during a 12
     month period  Total # persons in the population at the midpoint
     of the period
    Cause specific death rates: # deaths from a specific disease 
     # persons in the population at the midpoint of the period
    Age specific death rates: # deaths in a specific age group  #
     persons in that age group; Usually X 100,000
    Case fatality rate: Represents the risk of dying over a specified
     period of time for people with a certain disease
    Proportionate mortality ratio: Represents the proportion of total
     deaths that are due to a specific cause.
         Does not represent the risk of dying.
         # deaths from a specific disease  Total # deaths in the population X
          100 to express as a percent
Other Rates To Consider
  Gender Specific
  Race Specific
  Infant Mortality Rates
        Infant Mortality Rate – Birth to 1 year; Denominator
         is live births
           No.  of deaths < 1 year of age/No. of live
            births
        Neonatal Mortality Rate
        Post-neonatal Mortality Rate
        Perinatal Mortality Rate
Years of Productive Life Lost before Age 65 among
Children less than 20 Years


   1400
                                     Injuries
   1200
                                     Congenital Anomalies
   1000
   800                               Prematurity

   600                               Sudden Infant Death
   400                               Syndrome
                                     Cancer
   200
      0                              Respiratory Disease
              YPPL in Thousands
Incidence And Prevalence
Knowing Which Is Which
  Incidence measures the number of new cases
   in an at-risk population
  Prevalence measures the number of existing
   cases in an at-risk population
  Point Prevalence - the number of existing
   cases of a disease at a specific period of time.
   This includes new cases (Incidence).
  Period Prevalence - refers to the number of
   cases during a period or interval. This can
   include new and recurring cases.
Uses of Incidence and
Prevalence
    Prevalence is useful as planning tool
    Can be used to express burden of some
     attribute in the population
    Can monitor control programs for chronic
     illness
    Point prevalence can track illness over time
    Incidence rates are fundamental tools for
     etiologic studies of acute and chronic illness
Uses of Incidence and
Prevalence
  Comparing incidence between groups is useful
   for measuring affects of risk between
   populations
  High prevalence does not signify risk, it may
   merely reflect a change in survival rate
  Low prevalence may reflect a rapidly fatal
   disease (or easily curable)
  Prevalence favors inclusion of chronic illness
   over acute illness
Determining the Case Fatality
Rate

  Country   No. of Persons    1-Year Case Fatality
            in Population     Rate
                              Cerebrovascular
                              Disease (Pct.)
  A                 250,000                    10

  B                 100,000                    25

  C                  50,000                    50

  D                 250,000                    20
Determining the Case Fatality
Rate
  To determine which country has the largest
   annual number of new cases - obtain the rate
   of cases per 10,000 and compare it to the total
   population.
  For example, country A has 4 cases per
   10,000 and a total population of 250,000. For
   every 10,000 population there are 4 cases.
   Therefore, the number of new cases would be
   4/10,000:n/250,000.
Adjusted Rates
 Adjusted rates or standardized rates help remove
  the effects of differences in composition of various
  populations (for example, age differences).
 Direct Adjusted Rates - age specific rates observed
  in 2 or more study populations are applied to an
  arbitrarily chosen standard population.
 Indirect rate adjustment - compares 2 or more
  populations in which the age-specific rates are not
  known or are excessively variable because of the
  small size of the population. In this case, the rates of
  the more stable population are applied to the
  population of the smaller group.
Formula for Adjusted Rates

  Direct  Adjusted Rates =
     Σ(riNi)/Nt

  Indirect Adjusted Rates =
     dt/Σ(Rini)](Rt)
Controlling Infectious Disease
Controlling Infectious
Diseases
  Epidemic – the occurrence of cases of a
   condition in excess of what would be
   expected.
  Epidemics in US during 19th Century
      Smallpox
      Cholera

      Yellow Fever

      Typhoid Fever
How Infectious Diseases
Develop
  Characteristics of the Agent
  Reservoir of the Agent (where the agent
   lives and grows/host)
  Mode of Transmission
  Portal of Entry/Exit
  Susceptibility of the Host
Classes of Bacteria and Commonly
Associated Human Diseases

  Class            Disease
  Staphylococci    Toxic Shock Syndrome
  Streptococci     Streptococcal sore throat
  Neisseriae       Gonorrhea
  Legionellae      Pneumonia
  Mycobacteria     Tuberculosis
  Spriochetes      Syphilis
  Rickettsia       Typhus
  Chlamydiae       Urethritis
Characteristics of Infectious Agents

   Characterized in terms of biological
    classification
   Microbiological agents include:
       Bacteria
       Fungi

       Parasites

       Viruses
Detection of these agents

  Morphological identification in sections of
   tissue or stains of specimens
  Culture isolation
  Use of Fluorscein-labeled anti-body
   stains or immunologic assay
  DNA/RNA or DNA-DNA hybridization
  Antibody or cell-meditated immune
   responses
Components of accurately
identifying infectious diseases
   The specimen
   Adequacy of material being tested
   Selection of appropriate body area for
    testing
   Method of Collection
   Transport of the Specimen to the Lab
Detection Issues

  Pathogeneity – the ability of an organism
   to alter normal cellular and physiological
   processes
  Virulence – the ability of the organism to
   produce over infection
  Incubation Period – the time from point
   of infection to onset of disease
Detection Issues

  Reservoirs – can be living (human, animal,
   plant) or inanimate (soil, water)
  Clinical cases
        Those who manifest signs and symptoms of the
         disease (acute cases)
        Those who are infected but don’t show signs or
         symptoms (subclinical or inapparent cases)
    Carriers - those who serve as the source of
     the disease
Mode of Transmission

  Direct transmission - actual contact with
   an infected host
  Indirect transmission - contact with a
   contaminated object (contaminated
   needles, receptacles, etc.)
  Droplet spread - such as sneezing or
   coughing (inhalation)
Hosting the Agent
  Portal of Exit - where the organism leaves the body
  Portal of Entry - where the organism enters the body
  Host Susceptibility - depends on genetic factors, general
   health, and immunity. This usually refers to the condition of
   the host and the level of resistance.
        Passive natural immunity - passed from the mother to the
         fetus
        Passive Artificial Immunity - inoculation of specific protective
         antibodies
  Active Immunity can be natural (previous exposure to
   disease or previous exposure to preventative measures)
  To develop disease, individual must be susceptible and
   exposed

				
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