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  • Introduction to Epidemiology Dr. Abdelmageed Osman Musa
  • Epidemiology

    1. 1. Epidemiology Abdelmageed Osman Musa Associate Prof.
    2. 2. Introduction <ul><li>Contents of the course : </li></ul><ul><ul><li>Definition </li></ul></ul><ul><ul><li>Epidemiological Studies </li></ul></ul><ul><ul><li>Uses of Epidemiology </li></ul></ul><ul><ul><li>Epidemiology of infectious Diseases </li></ul></ul><ul><ul><li>Control of epidemics </li></ul></ul><ul><ul><li>Epidemiology of NCD </li></ul></ul>December 25, 2011 Epedimology
    3. 3. December 25, 2011 Epedimology 1. Definition
    4. 4. Definition of Epidemiology <ul><li>It is the study of distribution, determinants and frequencies of diseases </li></ul>December 25, 2011 Epedimology
    5. 5. Distribution of Disease <ul><li>Diseases are distributed according to: </li></ul><ul><ul><li>Place </li></ul></ul><ul><ul><li>Person </li></ul></ul><ul><ul><li>Time </li></ul></ul><ul><li>Study of distribution of diseases is essential in descriptive studies </li></ul>December 25, 2011 Epedimology
    6. 6. Place Distribution (Geographical distribution) <ul><li>Geography of diseases can identify the role of the following factors in disease causation: </li></ul><ul><ul><li>Genes, </li></ul></ul><ul><ul><li>Environment, </li></ul></ul><ul><ul><li>Culture, </li></ul></ul><ul><ul><li>Nutrition, </li></ul></ul><ul><ul><li>Socio-economic and </li></ul></ul><ul><ul><li>Cultural factors </li></ul></ul>December 25, 2011 Epedimology
    7. 7. Person Distribution <ul><li>In descriptive studies persons should be defined by: </li></ul><ul><ul><li>Age </li></ul></ul><ul><ul><li>Ethnicity </li></ul></ul><ul><ul><li>Sex </li></ul></ul><ul><ul><li>Occupation </li></ul></ul><ul><ul><li>Marital status </li></ul></ul><ul><ul><li>Behaviour </li></ul></ul>December 25, 2011 Epedimology
    8. 8. Distribution of diseases according to age <ul><li>Age is strongly related to disease: </li></ul><ul><ul><li>Certain diseases are frequent in specific age (measles in childhood, cancer in middle age, atherosclerosis in old age) </li></ul></ul><ul><ul><li>Bimodality: some diseases affect 2 age groups (Hodgkin's disease) – 20 and 80 years </li></ul></ul><ul><ul><li>Some diseases are more serious and progressive in specific age groups </li></ul></ul>December 25, 2011 Epedimology
    9. 9. Distribution of diseases according to sex <ul><li>Biological differences (e.g. Hormonal disorders) </li></ul><ul><li>Cultural behavior (e.g. 4:1 male to female lung cancers due to smoking, and so alcohol car accidents . .) </li></ul><ul><li>Some diseases are more frequent in male: duodenal ulcer, CHD .. </li></ul><ul><li>Some diseases are more severe in females (CVA) </li></ul>December 25, 2011 Epedimology
    10. 10. Distribution of diseases according to ethnicity <ul><li>Some diseases are more frequent among specific racial groups: </li></ul><ul><ul><li>Essential hypertension </li></ul></ul><ul><ul><li>CHD </li></ul></ul><ul><ul><li>Cancers </li></ul></ul><ul><ul><li>Sickle cell anaemia </li></ul></ul>December 25, 2011 Epedimology
    11. 11. Distribution of diseases according to marital status <ul><li>Mortality rates is lower for married males may be due to: </li></ul><ul><ul><li>Healthy persons are more likely to get married </li></ul></ul><ul><li>Married persons had healthy lifestyle </li></ul><ul><li>STDs are more frequent among unmarried </li></ul><ul><li>Ca cervix is more common among married women </li></ul>December 25, 2011 Epedimology
    12. 12. Distribution of diseases according to occupation <ul><li>Occupation may alter the habit pattern of employees e.g. (night shifts may alter sleep ..) </li></ul><ul><li>Occupational hazards may affect health (biological, chemical, physical, psychosocial, mechanical) </li></ul>December 25, 2011 Epedimology
    13. 13. Distribution of disease according to behaviour <ul><li>Behaviour factors (smoking, alcohol, sedentary life, overeating, drug abuse, stress ..) </li></ul><ul><li>Behaviour is a strong risk factor in modern-day diseases: </li></ul><ul><ul><li>CHD </li></ul></ul><ul><ul><li>Cancers </li></ul></ul><ul><ul><li>CHD </li></ul></ul><ul><ul><li>Accidents </li></ul></ul>December 25, 2011 Epedimology
    14. 14. Time distribution <ul><li>Short-term fluctuations (epidemics) </li></ul><ul><li>Periodic fluctuations (seasonal trend) </li></ul><ul><li>Long term fluctuations (e.g. diabetes show a consistent upward trend in the developed countries during the last 50 years </li></ul>December 25, 2011 Epedimology
    15. 15. Determinants of Diseases <ul><li>Biological factors (Bacteria, viruses etc) </li></ul><ul><li>Chemical factors (pesticides, lead etc) </li></ul><ul><li>Physical factors (radiation, heat ..) </li></ul><ul><li>Mechanical factors (accidents) </li></ul><ul><li>Psychosocial factors (stress, alcohol etc) </li></ul>December 25, 2011 Epedimology
    16. 16. Frequencies of Diseases <ul><li>Fertility Rates </li></ul><ul><li>Morbidity Rates </li></ul><ul><li>Mortality Rates </li></ul>December 25, 2011 Epedimology
    17. 17. Fertility Rates <ul><li>Crude Birth Rate (1000): </li></ul><ul><li>Number of live births during the year </li></ul><ul><li>Population </li></ul><ul><li>General fertility Rate (1000): </li></ul><ul><li>No of live births in an area during a year </li></ul><ul><li>Female 15 -49 </li></ul>December 25, 2011 Epedimology
    18. 18. Morbidity Rates <ul><li>Incidence (1000): </li></ul><ul><li>Number of new cases of a specific disease during a given period </li></ul><ul><li>Population at risk </li></ul><ul><li>Prevalence (100): </li></ul><ul><li>Number of new and old cases of a specific disease during a given period </li></ul><ul><li>Population at risk </li></ul>December 25, 2011 Epedimology
    19. 19. Mortality Rates <ul><li>Crude death rate (1000) </li></ul><ul><li>No of deaths during a year </li></ul><ul><li>Population </li></ul><ul><li>Specific death rate </li></ul><ul><li>Case fatality rate (100): </li></ul><ul><li>Deaths due to a particular disease </li></ul><ul><li>Total no of cases due to the same diseae </li></ul>December 25, 2011 Epedimology
    20. 20. Survival Rate <ul><li>Survival rate (100) </li></ul><ul><li>Total patients alive after 5 years </li></ul><ul><li>Total patients diagnosed or treated </li></ul>December 25, 2011 Epedimology
    21. 21. Standardize Mortality Rate <ul><li>SMR (100) </li></ul><ul><li>Observed deaths </li></ul><ul><li>Expected deaths </li></ul>December 25, 2011 Epedimology
    22. 22. Years of potential life lost ( YPLL ) <ul><li>Is an estimate of the average years a person would have lived if he or she had not died prematurely </li></ul><ul><li>The reference age should correspond roughly to the life expectancy of the population under study </li></ul>December 25, 2011 Epedimology
    23. 23. Person-years of potential life lost in the United States in 2006 <ul><li>Cancer 8,628,000 </li></ul><ul><li>Heart disease and strokes 8,760,000 </li></ul><ul><li>Accidents and other injuries 5,873,000 </li></ul><ul><li>All other causes 13,649,000 person-years </li></ul>December 25, 2011 Epedimology
    24. 24. The disability-adjusted life year (DALY) <ul><li>It is a measure of overall disease burden </li></ul><ul><li>Expressed as the number of years lost due to ill-health, disability or early death. </li></ul><ul><li>Originally developed by Harvard University for the World Bank in 1990, </li></ul><ul><li>The WHO adopted the method in 2000 </li></ul><ul><li>The DALY is becoming increasingly common in the field of public health and health impact assessment </li></ul>December 25, 2011 Epedimology
    25. 25. DALYs in Millions <ul><li>HIV/AIDS 46.7 </li></ul><ul><li>Lower respiratory infections 42.2 </li></ul><ul><li>Diarrhoeal diseases 32.2 </li></ul><ul><li>Malaria 30.9 8.2 4 </li></ul><ul><li>Neonatal infections and others - 13.4 3. </li></ul><ul><li>Prematurity and low birth weight 11.3 </li></ul><ul><li>Tuberculosis 10.8 </li></ul><ul><li>Road traffic accidents </li></ul><ul><li>COPD 3.1 </li></ul><ul><li>Protein-energy malnutrition 7.1 </li></ul>December 25, 2011 Epedimology
    26. 26. December 25, 2011 Epedimology 2. Epidemiological Studies
    27. 27. Epidemiological studies <ul><li>Main Types of epidemiological Studies: </li></ul><ul><li>Descriptive Studies </li></ul><ul><li>Analytical (Comparative Studies </li></ul><ul><li>Interventional studies (experimental) </li></ul>December 25, 2011 Epedimology
    28. 28. Nomination <ul><li>Case control study (retrospective) e.g. Ca lung --- smoking </li></ul><ul><li>Cohort study (prospective) e.g. smoking -- Ca lung </li></ul><ul><li>Cross-sectional Study: a study in a known short period of time (Picture) </li></ul><ul><li>Longitudinal Study: observation is repeated in the same population over a long period of time (film) </li></ul><ul><li>Facility-Based Study </li></ul><ul><li>Community-Based study </li></ul>December 25, 2011 Epedimology
    29. 29. Uses of Epidemiological Studies <ul><li>Descriptive studies: To develop hypothesizes </li></ul><ul><li>Analytical Studies: To test hypothesis </li></ul><ul><li>Experimental studies: To confirm hypotheisi </li></ul>December 25, 2011 Epedimology
    30. 30. December 25, 2011 Epedimology 3. Uses of epidemiology
    31. 31. Uses of Epidemiology <ul><li>Community diagnosis </li></ul><ul><li>Control of epidemics </li></ul><ul><li>Prevention and control of diseases </li></ul><ul><li>Evaluation of curative and preventive measures </li></ul><ul><li>Study of natural history of diseases </li></ul><ul><li>Planning for Health Services </li></ul><ul><li>Implementation of H. Services </li></ul>December 25, 2011 Epedimology
    32. 32. December 25, 2011 Epedimology 4. Epidemiology of Infectious diseases
    33. 33. Epidemiology of Infectious disease <ul><li>Definitions </li></ul><ul><li>Agent </li></ul><ul><li>Concepts of causation </li></ul><ul><li>Disease Transmission </li></ul><ul><li>Susceptible Host </li></ul><ul><li>Prevention </li></ul>December 25, 2011 Epedimology
    34. 34. Definitions <ul><li>Infectious disease = Clinically manifested disease resulting from an infection </li></ul><ul><li>Contagious disease = diseases transmitted through contact (scabies, trachoma, leprosy) </li></ul><ul><li>Communicable disease = infectious illness transmitted directly or indirectly </li></ul>December 25, 2011 Epedimology
    35. 35. cont. definitions <ul><li>Endemic = constant presence of a disease in an area </li></ul><ul><li>Nosocomial = hospital acquired infection </li></ul><ul><li>Iatrogenic = physician induced disease </li></ul><ul><li>Exotic = disease transported in a country </li></ul>December 25, 2011 Epedimology
    36. 36. Concepts of causation <ul><li>Supernatural theory </li></ul><ul><li>Germ theory </li></ul><ul><li>Multifactorial Theory </li></ul><ul><li>Web causation Theory </li></ul>December 25, 2011 Epedimology
    37. 37. Epidemiological Triangle December 25, 2011 Epedimology Agent Host Environment
    38. 38. Agent of infectious disease <ul><li>It is a biological agent: </li></ul><ul><li>Viruses (HIV ,,) </li></ul><ul><li>Ricketsiae (Typhus ..) </li></ul><ul><li>Fungi (Candida ..) </li></ul><ul><li>Bacteria (Streptococcus) </li></ul><ul><li>Protozoa (Plasmodium ..) </li></ul><ul><li>Metazoa (tapeworms) </li></ul>December 25, 2011 Epedimology
    39. 39. Nominations` <ul><li>Infectivity: ability of infectious agent to invade and multiply in human being </li></ul><ul><li>Pathogenicity: ability to induce clinical disease </li></ul><ul><li>Virulence: Power of killing </li></ul>December 25, 2011 Epedimology
    40. 40. Susceptible Host <ul><li>Host factors: </li></ul><ul><li>Demographic (age, sex, ethnicity ..) </li></ul><ul><li>Genetics </li></ul><ul><li>Immunity </li></ul><ul><li>Social and economical </li></ul><ul><li>Life style </li></ul>December 25, 2011 Epedimology
    41. 41. Environmental Factor <ul><li>Environmental factors related to the: </li></ul><ul><li>Host </li></ul><ul><li>Agent </li></ul><ul><li>Vector </li></ul>December 25, 2011 Epedimology
    42. 42. Infectious Agent <ul><li>Bacteria </li></ul><ul><li>Virus </li></ul><ul><li>Fungi </li></ul><ul><li>Protozoa </li></ul><ul><li>………… </li></ul>December 25, 2011 Epedimology
    43. 43. Chain of infection <ul><li>Infectious agent </li></ul><ul><li>Reservoir </li></ul><ul><li>Portal of Exit </li></ul><ul><li>Means of transmission </li></ul><ul><li>Portal of entry </li></ul><ul><li>Susceptible Host </li></ul>December 25, 2011 Epedimology
    44. 44. Reservoir <ul><li>People </li></ul><ul><li>Equipment </li></ul><ul><li>Water </li></ul><ul><li>……………… . </li></ul>December 25, 2011 Epedimology
    45. 45. Portal of Exit <ul><li>Excretions </li></ul><ul><li>Droplet </li></ul><ul><li>Skin </li></ul><ul><li>…………… </li></ul>December 25, 2011 Epedimology
    46. 46. December 25, 2011 Epedimology Means of Transmission
    47. 47. 1. Droplet contact <ul><li>coughs or sneezes coughing or sneezing include (at least): </li></ul><ul><ul><li>Bacterial Meningitis </li></ul></ul><ul><ul><li>Common cold </li></ul></ul><ul><ul><li>Influenza </li></ul></ul><ul><ul><li>Streptococcal throat </li></ul></ul><ul><ul><li>Tuberculosis </li></ul></ul>December 25, 2011 Epedimology
    48. 48. 2. Fecal-Oral Transmission <ul><li>Direct contact is rare in this route </li></ul><ul><li>Indirect through water, food is common </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Cholera </li></ul></ul><ul><ul><li>Hepatitis A </li></ul></ul>December 25, 2011 Epedimology
    49. 49. 3. Sexual Transmission <ul><li>Direct Transmission (contact during intercourse) </li></ul><ul><li>Indirect from secretions (semen or fluid secreted by female) examples: </li></ul><ul><ul><li>HIV </li></ul></ul><ul><ul><li>Gonorrhea </li></ul></ul><ul><ul><li>Hepatitis B </li></ul></ul>December 25, 2011 Epedimology
    50. 50. 4. Oral Transmission <ul><li>direct oral contact such as Kissing </li></ul><ul><li>indirect by sharing a drinking glass or a cigarette. </li></ul><ul><li>Most of diseases that transmitted by oral contact are forms of herpes </li></ul>December 25, 2011 Epedimology
    51. 51. 5. Transmission by direct contact <ul><li>They are called contagious </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Impetigo </li></ul></ul><ul><ul><li>Syphilis </li></ul></ul><ul><ul><li>Leprosy </li></ul></ul>December 25, 2011 Epedimology
    52. 52. 6. Vertical Transmission <ul><li>From mother to child (in-utero or during childbirth), </li></ul><ul><li>Examples: </li></ul><ul><ul><li>HIV </li></ul></ul><ul><ul><li>Hepatitis B </li></ul></ul><ul><ul><li>Syphilis </li></ul></ul>December 25, 2011 Epedimology
    53. 53. 7. Iatrogenic Transmission <ul><li>Transmission due to medical procedures </li></ul>December 25, 2011 Epedimology
    54. 54. 8. Vector borne transmission <ul><li>A vector is an organism that transmits infection </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Flies – Gastroenteritis </li></ul></ul><ul><ul><li>Mosquitoes: Malaria, Trypansomiasis, </li></ul></ul>December 25, 2011 Epedimology
    55. 55. Portal of Entry <ul><li>Broken skin </li></ul><ul><li>Mucus membranes </li></ul><ul><li>Gastrointestinal/respiratory/urinary tract </li></ul>December 25, 2011 Epedimology
    56. 56. Susceptible Host <ul><li>Neonates </li></ul><ul><li>Diabetes </li></ul><ul><li>Immunosuppressant </li></ul><ul><li>Cardiopulmonary disease </li></ul>December 25, 2011 Epedimology
    57. 57. December 25, 2011 Epedimology 5. Control of epidemics
    58. 58. Definition of an epidemic <ul><li>Abnormal increase of incidence of a disease (≥ 2 SD) or </li></ul><ul><li>Doubling of cases during a week </li></ul><ul><li>Appearance of unknown disease in an area </li></ul>December 25, 2011 Epedimology
    59. 59. Investigation of an epidemic <ul><li>Verification of diagnosis </li></ul><ul><li>Confirmation of an epidemic </li></ul><ul><li>Defining population at risk </li></ul><ul><li>Search for other cases </li></ul><ul><li>Data analysis </li></ul><ul><li>Formulation of hypothesis </li></ul><ul><li>Testing hypothesis </li></ul><ul><li>Evaluation of ecological factors </li></ul><ul><li>Further investigation of population at risk </li></ul><ul><li>Writing report </li></ul>December 25, 2011 Epedimology
    60. 60. Control of epidemic <ul><li>Treatment </li></ul><ul><li>Control </li></ul><ul><li>Notification </li></ul>December 25, 2011 Epedimology
    61. 61. December 25, 2011 Epedimology 6. Epidemiology of Non-communicable diseases
    62. 62. Definition <ul><li>Chronic diseases which have one or more of the following characteristics: </li></ul><ul><li>permanent </li></ul><ul><li>have residual disability </li></ul><ul><li>non-reversible </li></ul><ul><li>require special training of the patient for rehabilitation </li></ul><ul><li>require a long period of supervision, observation or care </li></ul>December 25, 2011 Epedimology
    63. 63. Examples of Non-communicable Diseases <ul><li>Cardiovascular diseases </li></ul><ul><li>CHD </li></ul><ul><li>Ca </li></ul><ul><li>Hypertension </li></ul><ul><li>diabetes </li></ul><ul><li>Accident </li></ul><ul><li>Blindness </li></ul><ul><li>Obesity </li></ul>December 25, 2011 Epedimology
    64. 64. The Problem <ul><li>32 million people die due to non-communicable diseases every year </li></ul><ul><li>Affects adults </li></ul><ul><li>Affects the quality of life </li></ul><ul><li>It is increasing, mainly in developing countries </li></ul><ul><ul><li>Life expectancy is increasing </li></ul></ul><ul><ul><li>Change of life style </li></ul></ul>December 25, 2011 Epedimology
    65. 65. Impact of Non-communicable diseases on the lives of people <ul><li>Disabilities </li></ul><ul><li>Family hardship </li></ul>December 25, 2011 Epedimology
    66. 66. Risk factors of Non-communicable diseases <ul><li>Smoking, Alcohol </li></ul><ul><li>Inability to obtain preventive health services </li></ul><ul><li>Life style changes </li></ul><ul><li>Stress </li></ul><ul><li>Environmental risk factors: (Occupational hazards, Pollution (air, water) </li></ul>December 25, 2011 Epedimology
    67. 67. December 25, 2011 Epedimology Prevention of Diseases
    68. 68. Definition of Disease Prevention <ul><li>Any activity which reduces morbidity and mortality of diseases </li></ul>December 25, 2011 Epedimology
    69. 69. Primordial Level (Health Promotion) <ul><li>Definition: Helping people to improve Health </li></ul><ul><li>Interventions of Health Promotion: </li></ul><ul><ul><li>Health Education promoting healthy lifestyle </li></ul></ul><ul><ul><li>Environmental modification </li></ul></ul><ul><ul><li>Nutritional Interventions </li></ul></ul>December 25, 2011 Epedimology
    70. 70. Levels of Prevention <ul><li>Primary Level </li></ul><ul><li>Secondary Level </li></ul><ul><li>Tertiary Level </li></ul>December 25, 2011 Epedimology
    71. 71. Primary Level of Prevention <ul><li>Actions taken before the onset of a specific disease </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Bed nets </li></ul></ul><ul><ul><li>Vaccines </li></ul></ul><ul><ul><li>… . </li></ul></ul>December 25, 2011 Epedimology
    72. 72. Secondary Level of Prevention <ul><li>Early diagnosis and adequate treatment </li></ul>December 25, 2011 Epedimology
    73. 73. Tertiary Level of Prevention <ul><li>Tertiary level of Prevention ( Rehabilitation) </li></ul><ul><ul><li>Medical rehabilitation </li></ul></ul><ul><ul><li>Occupational rehabilitation </li></ul></ul><ul><ul><li>Social rehabilitation </li></ul></ul><ul><ul><li>Psychological rehabilitation </li></ul></ul>December 25, 2011 Epedimology
    74. 74. Disease Control <ul><li>An ongoing operations aimed at reducing: </li></ul><ul><ul><li>The incidence of disease </li></ul></ul><ul><ul><li>The duration of disease </li></ul></ul><ul><ul><li>Complication of the disease </li></ul></ul><ul><ul><li>The financial burden to the community </li></ul></ul><ul><li>It concentrates on primary and secondary prevention </li></ul>December 25, 2011 Epedimology
    75. 75. Thank You <ul><li>References: </li></ul><ul><ul><li>Park’s Textbook of Preventive and Social Medicine </li></ul></ul><ul><ul><li>طب المجتمع – منظمة الصحة العالمية </li></ul></ul>December 25, 2011 Epedimology