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Epidemiology
 

Epidemiology

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  • Introduction to Epidemiology Dr. Abdelmageed Osman Musa

Epidemiology Epidemiology Presentation Transcript

  • Epidemiology Abdelmageed Osman Musa Associate Prof.
  • Introduction
    • Contents of the course :
      • Definition
      • Epidemiological Studies
      • Uses of Epidemiology
      • Epidemiology of infectious Diseases
      • Control of epidemics
      • Epidemiology of NCD
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology 1. Definition
  • Definition of Epidemiology
    • It is the study of distribution, determinants and frequencies of diseases
    December 25, 2011 Epedimology
  • Distribution of Disease
    • Diseases are distributed according to:
      • Place
      • Person
      • Time
    • Study of distribution of diseases is essential in descriptive studies
    December 25, 2011 Epedimology
  • Place Distribution (Geographical distribution)
    • Geography of diseases can identify the role of the following factors in disease causation:
      • Genes,
      • Environment,
      • Culture,
      • Nutrition,
      • Socio-economic and
      • Cultural factors
    December 25, 2011 Epedimology
  • Person Distribution
    • In descriptive studies persons should be defined by:
      • Age
      • Ethnicity
      • Sex
      • Occupation
      • Marital status
      • Behaviour
    December 25, 2011 Epedimology
  • Distribution of diseases according to age
    • Age is strongly related to disease:
      • Certain diseases are frequent in specific age (measles in childhood, cancer in middle age, atherosclerosis in old age)
      • Bimodality: some diseases affect 2 age groups (Hodgkin's disease) – 20 and 80 years
      • Some diseases are more serious and progressive in specific age groups
    December 25, 2011 Epedimology
  • Distribution of diseases according to sex
    • Biological differences (e.g. Hormonal disorders)
    • Cultural behavior (e.g. 4:1 male to female lung cancers due to smoking, and so alcohol car accidents . .)
    • Some diseases are more frequent in male: duodenal ulcer, CHD ..
    • Some diseases are more severe in females (CVA)
    December 25, 2011 Epedimology
  • Distribution of diseases according to ethnicity
    • Some diseases are more frequent among specific racial groups:
      • Essential hypertension
      • CHD
      • Cancers
      • Sickle cell anaemia
    December 25, 2011 Epedimology
  • Distribution of diseases according to marital status
    • Mortality rates is lower for married males may be due to:
      • Healthy persons are more likely to get married
    • Married persons had healthy lifestyle
    • STDs are more frequent among unmarried
    • Ca cervix is more common among married women
    December 25, 2011 Epedimology
  • Distribution of diseases according to occupation
    • Occupation may alter the habit pattern of employees e.g. (night shifts may alter sleep ..)
    • Occupational hazards may affect health (biological, chemical, physical, psychosocial, mechanical)
    December 25, 2011 Epedimology
  • Distribution of disease according to behaviour
    • Behaviour factors (smoking, alcohol, sedentary life, overeating, drug abuse, stress ..)
    • Behaviour is a strong risk factor in modern-day diseases:
      • CHD
      • Cancers
      • CHD
      • Accidents
    December 25, 2011 Epedimology
  • Time distribution
    • Short-term fluctuations (epidemics)
    • Periodic fluctuations (seasonal trend)
    • Long term fluctuations (e.g. diabetes show a consistent upward trend in the developed countries during the last 50 years
    December 25, 2011 Epedimology
  • Determinants of Diseases
    • Biological factors (Bacteria, viruses etc)
    • Chemical factors (pesticides, lead etc)
    • Physical factors (radiation, heat ..)
    • Mechanical factors (accidents)
    • Psychosocial factors (stress, alcohol etc)
    December 25, 2011 Epedimology
  • Frequencies of Diseases
    • Fertility Rates
    • Morbidity Rates
    • Mortality Rates
    December 25, 2011 Epedimology
  • Fertility Rates
    • Crude Birth Rate (1000):
    • Number of live births during the year
    • Population
    • General fertility Rate (1000):
    • No of live births in an area during a year
    • Female 15 -49
    December 25, 2011 Epedimology
  • Morbidity Rates
    • Incidence (1000):
    • Number of new cases of a specific disease during a given period
    • Population at risk
    • Prevalence (100):
    • Number of new and old cases of a specific disease during a given period
    • Population at risk
    December 25, 2011 Epedimology
  • Mortality Rates
    • Crude death rate (1000)
    • No of deaths during a year
    • Population
    • Specific death rate
    • Case fatality rate (100):
    • Deaths due to a particular disease
    • Total no of cases due to the same diseae
    December 25, 2011 Epedimology
  • Survival Rate
    • Survival rate (100)
    • Total patients alive after 5 years
    • Total patients diagnosed or treated
    December 25, 2011 Epedimology
  • Standardize Mortality Rate
    • SMR (100)
    • Observed deaths
    • Expected deaths
    December 25, 2011 Epedimology
  • Years of potential life lost ( YPLL )
    • Is an estimate of the average years a person would have lived if he or she had not died prematurely
    • The reference age should correspond roughly to the life expectancy of the population under study
    December 25, 2011 Epedimology
  • Person-years of potential life lost in the United States in 2006
    • Cancer 8,628,000
    • Heart disease and strokes 8,760,000
    • Accidents and other injuries 5,873,000
    • All other causes 13,649,000 person-years
    December 25, 2011 Epedimology
  • The disability-adjusted life year (DALY)
    • It is a measure of overall disease burden
    • Expressed as the number of years lost due to ill-health, disability or early death.
    • Originally developed by Harvard University for the World Bank in 1990,
    • The WHO adopted the method in 2000
    • The DALY is becoming increasingly common in the field of public health and health impact assessment
    December 25, 2011 Epedimology
  • DALYs in Millions
    • HIV/AIDS 46.7
    • Lower respiratory infections 42.2
    • Diarrhoeal diseases 32.2
    • Malaria 30.9 8.2 4
    • Neonatal infections and others - 13.4 3.
    • Prematurity and low birth weight 11.3
    • Tuberculosis 10.8
    • Road traffic accidents
    • COPD 3.1
    • Protein-energy malnutrition 7.1
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology 2. Epidemiological Studies
  • Epidemiological studies
    • Main Types of epidemiological Studies:
    • Descriptive Studies
    • Analytical (Comparative Studies
    • Interventional studies (experimental)
    December 25, 2011 Epedimology
  • Nomination
    • Case control study (retrospective) e.g. Ca lung --- smoking
    • Cohort study (prospective) e.g. smoking -- Ca lung
    • Cross-sectional Study: a study in a known short period of time (Picture)
    • Longitudinal Study: observation is repeated in the same population over a long period of time (film)
    • Facility-Based Study
    • Community-Based study
    December 25, 2011 Epedimology
  • Uses of Epidemiological Studies
    • Descriptive studies: To develop hypothesizes
    • Analytical Studies: To test hypothesis
    • Experimental studies: To confirm hypotheisi
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology 3. Uses of epidemiology
  • Uses of Epidemiology
    • Community diagnosis
    • Control of epidemics
    • Prevention and control of diseases
    • Evaluation of curative and preventive measures
    • Study of natural history of diseases
    • Planning for Health Services
    • Implementation of H. Services
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology 4. Epidemiology of Infectious diseases
  • Epidemiology of Infectious disease
    • Definitions
    • Agent
    • Concepts of causation
    • Disease Transmission
    • Susceptible Host
    • Prevention
    December 25, 2011 Epedimology
  • Definitions
    • Infectious disease = Clinically manifested disease resulting from an infection
    • Contagious disease = diseases transmitted through contact (scabies, trachoma, leprosy)
    • Communicable disease = infectious illness transmitted directly or indirectly
    December 25, 2011 Epedimology
  • cont. definitions
    • Endemic = constant presence of a disease in an area
    • Nosocomial = hospital acquired infection
    • Iatrogenic = physician induced disease
    • Exotic = disease transported in a country
    December 25, 2011 Epedimology
  • Concepts of causation
    • Supernatural theory
    • Germ theory
    • Multifactorial Theory
    • Web causation Theory
    December 25, 2011 Epedimology
  • Epidemiological Triangle December 25, 2011 Epedimology Agent Host Environment
  • Agent of infectious disease
    • It is a biological agent:
    • Viruses (HIV ,,)
    • Ricketsiae (Typhus ..)
    • Fungi (Candida ..)
    • Bacteria (Streptococcus)
    • Protozoa (Plasmodium ..)
    • Metazoa (tapeworms)
    December 25, 2011 Epedimology
  • Nominations`
    • Infectivity: ability of infectious agent to invade and multiply in human being
    • Pathogenicity: ability to induce clinical disease
    • Virulence: Power of killing
    December 25, 2011 Epedimology
  • Susceptible Host
    • Host factors:
    • Demographic (age, sex, ethnicity ..)
    • Genetics
    • Immunity
    • Social and economical
    • Life style
    December 25, 2011 Epedimology
  • Environmental Factor
    • Environmental factors related to the:
    • Host
    • Agent
    • Vector
    December 25, 2011 Epedimology
  • Infectious Agent
    • Bacteria
    • Virus
    • Fungi
    • Protozoa
    • …………
    December 25, 2011 Epedimology
  • Chain of infection
    • Infectious agent
    • Reservoir
    • Portal of Exit
    • Means of transmission
    • Portal of entry
    • Susceptible Host
    December 25, 2011 Epedimology
  • Reservoir
    • People
    • Equipment
    • Water
    • ……………… .
    December 25, 2011 Epedimology
  • Portal of Exit
    • Excretions
    • Droplet
    • Skin
    • ……………
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology Means of Transmission
  • 1. Droplet contact
    • coughs or sneezes coughing or sneezing include (at least):
      • Bacterial Meningitis
      • Common cold
      • Influenza
      • Streptococcal throat
      • Tuberculosis
    December 25, 2011 Epedimology
  • 2. Fecal-Oral Transmission
    • Direct contact is rare in this route
    • Indirect through water, food is common
    • Examples:
      • Cholera
      • Hepatitis A
    December 25, 2011 Epedimology
  • 3. Sexual Transmission
    • Direct Transmission (contact during intercourse)
    • Indirect from secretions (semen or fluid secreted by female) examples:
      • HIV
      • Gonorrhea
      • Hepatitis B
    December 25, 2011 Epedimology
  • 4. Oral Transmission
    • direct oral contact such as Kissing
    • indirect by sharing a drinking glass or a cigarette.
    • Most of diseases that transmitted by oral contact are forms of herpes
    December 25, 2011 Epedimology
  • 5. Transmission by direct contact
    • They are called contagious
    • Examples:
      • Impetigo
      • Syphilis
      • Leprosy
    December 25, 2011 Epedimology
  • 6. Vertical Transmission
    • From mother to child (in-utero or during childbirth),
    • Examples:
      • HIV
      • Hepatitis B
      • Syphilis
    December 25, 2011 Epedimology
  • 7. Iatrogenic Transmission
    • Transmission due to medical procedures
    December 25, 2011 Epedimology
  • 8. Vector borne transmission
    • A vector is an organism that transmits infection
    • Examples:
      • Flies – Gastroenteritis
      • Mosquitoes: Malaria, Trypansomiasis,
    December 25, 2011 Epedimology
  • Portal of Entry
    • Broken skin
    • Mucus membranes
    • Gastrointestinal/respiratory/urinary tract
    December 25, 2011 Epedimology
  • Susceptible Host
    • Neonates
    • Diabetes
    • Immunosuppressant
    • Cardiopulmonary disease
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology 5. Control of epidemics
  • Definition of an epidemic
    • Abnormal increase of incidence of a disease (≥ 2 SD) or
    • Doubling of cases during a week
    • Appearance of unknown disease in an area
    December 25, 2011 Epedimology
  • Investigation of an epidemic
    • Verification of diagnosis
    • Confirmation of an epidemic
    • Defining population at risk
    • Search for other cases
    • Data analysis
    • Formulation of hypothesis
    • Testing hypothesis
    • Evaluation of ecological factors
    • Further investigation of population at risk
    • Writing report
    December 25, 2011 Epedimology
  • Control of epidemic
    • Treatment
    • Control
    • Notification
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology 6. Epidemiology of Non-communicable diseases
  • Definition
    • Chronic diseases which have one or more of the following characteristics:
    • permanent
    • have residual disability
    • non-reversible
    • require special training of the patient for rehabilitation
    • require a long period of supervision, observation or care
    December 25, 2011 Epedimology
  • Examples of Non-communicable Diseases
    • Cardiovascular diseases
    • CHD
    • Ca
    • Hypertension
    • diabetes
    • Accident
    • Blindness
    • Obesity
    December 25, 2011 Epedimology
  • The Problem
    • 32 million people die due to non-communicable diseases every year
    • Affects adults
    • Affects the quality of life
    • It is increasing, mainly in developing countries
      • Life expectancy is increasing
      • Change of life style
    December 25, 2011 Epedimology
  • Impact of Non-communicable diseases on the lives of people
    • Disabilities
    • Family hardship
    December 25, 2011 Epedimology
  • Risk factors of Non-communicable diseases
    • Smoking, Alcohol
    • Inability to obtain preventive health services
    • Life style changes
    • Stress
    • Environmental risk factors: (Occupational hazards, Pollution (air, water)
    December 25, 2011 Epedimology
  • December 25, 2011 Epedimology Prevention of Diseases
  • Definition of Disease Prevention
    • Any activity which reduces morbidity and mortality of diseases
    December 25, 2011 Epedimology
  • Primordial Level (Health Promotion)
    • Definition: Helping people to improve Health
    • Interventions of Health Promotion:
      • Health Education promoting healthy lifestyle
      • Environmental modification
      • Nutritional Interventions
    December 25, 2011 Epedimology
  • Levels of Prevention
    • Primary Level
    • Secondary Level
    • Tertiary Level
    December 25, 2011 Epedimology
  • Primary Level of Prevention
    • Actions taken before the onset of a specific disease
    • Examples:
      • Bed nets
      • Vaccines
      • … .
    December 25, 2011 Epedimology
  • Secondary Level of Prevention
    • Early diagnosis and adequate treatment
    December 25, 2011 Epedimology
  • Tertiary Level of Prevention
    • Tertiary level of Prevention ( Rehabilitation)
      • Medical rehabilitation
      • Occupational rehabilitation
      • Social rehabilitation
      • Psychological rehabilitation
    December 25, 2011 Epedimology
  • Disease Control
    • An ongoing operations aimed at reducing:
      • The incidence of disease
      • The duration of disease
      • Complication of the disease
      • The financial burden to the community
    • It concentrates on primary and secondary prevention
    December 25, 2011 Epedimology
  • Thank You
    • References:
      • Park’s Textbook of Preventive and Social Medicine
      • طب المجتمع – منظمة الصحة العالمية
    December 25, 2011 Epedimology