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Principles of Disease and Epidemiology

Principles of Disease and Epidemiology. Pathology. Study of Disease ETIOLOGY = cause of disease PATHOGENESIS = disease development. Infection and Disease Same or Different?. INFECTION – colonization of body by pathogenic microorganisms

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Principles of Disease and Epidemiology

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  1. Principles of DiseaseandEpidemiology

  2. Pathology • Study of Disease • ETIOLOGY = cause of disease • PATHOGENESIS = disease development

  3. Infection and DiseaseSame or Different? • INFECTION – colonization of body by pathogenic microorganisms • DISEASE – change in state of health as result of infection • ANSWER - ?

  4. 100,000,000,000,000(100 trillion) • Number of bacterial cells in and on the body • NORMAL FLORA – permanent bacterial residents of the body that usually DO NOT produce disease • TRANSIENT FLORA – microbes that are present for a few days or weeks and then disappear

  5. Skin Eyes Mouth Nose and Throat Large Intestine Urinary and Reproductive Tract Stomach and Small Intestine have very few bacteria Major locations of bacterial populations

  6. Host and Microbial Interaction • Microbial Antagonism – normal flora prevent the overgrowth of harmful microorganisms • Example – normal flora preventing the growth of the yeast Candida albicans • Disruption of the normal flora can lead to yeast infections

  7. Symbiosis Living Together COMMENSALISM One benefits Other unaffected MUTAULISM Both benefit PARASITISM One harmed Other benefits Host and Bacterial Relationships

  8. Opportunistic Pathogens • Microbes that ordinary do not cause disease in their normal habitat but do so in a different environment • Example – E. coli is generally harmless in the large intestine but can cause infection if it gets into the bladder.

  9. Koch’s Postulates • Cause and effect relationship between pathogen and disease • Established a set of experimental criterion for the etiology of ANY infectious disease

  10. What are Signs and Symptoms? • Symptom – subjective changes, something YOU feel that is not apparent to anyone else • Sign – objective changes that can be observed and measured

  11. Disease Interaction • COMMUNICABLE DISEASE – disease that can spread either directly or indirectly. Example?? • CONTAGIOUS DISEASE – disease that spreads easily. Example?? • NON-COMMUNICABLE DISEASE – disease that is not spread from one host to another. Example??

  12. Disease Occurrence • Incidence – number of people in a population who develop a disease during a particular time period • Indicator of spread of disease • Prevalence – number of people who develop a disease in a specified time regardless of when the disease first appeared

  13. Disease Occurrence • ENDEMIC DISEASE – always present in a population, example?? • EPIDEMIC DISEASE – many people in an area acquire a disease in a short period, example?? • PANDEMIC DISEASE – epidemic disease that occurs worldwide, example??

  14. Severity of Disease • ACUTE DISEASE – rapid development, short duration, example?? • CHRONIC DISEASE – slow development, long duration, example?? • LATENT DISEASE – causative agent remains inactive, example??

  15. Host Involvement • LOCAL INFECTION – small area of the body is involved • SYSTEMIC INFECTION – spread of microbes OR their products throughout the body.

  16. Host Involvement • Sepsis – toxic inflammation caused by spread of bacteria or toxins. • Septicemia (blood poisoning) – systemic infection. Bacteria multiplying in the blood. • Bacteremia – bacteria in the blood • Toxemia - toxins in the blood • Viremia - viruses in the blood

  17. Development of Disease

  18. Development of Disease • INCUBATION • PRODROMAL • PERIOD OF ILLNESS • PERIOD OF DECLINE • PERIOD OF CONVALESCENCE

  19. Reservoir of Infection Human Reservoir Carriers Animal reservoirs Zoonoses Non-living Reservoir Soil and water Source of Infection

  20. Transmission of Disease • CONTACT TRANSMISSION • VEHICLE TRANSMISSION • VECTORS

  21. Contact Transmission • Direct contact transmission – person to person; touching, kissing, etc. • Indirect contact transmission • FOMITE – non-living material, tissue, bedding, towels, cups, etc • Droplet transmission • Coughing, sneezing, laughing, talking

  22. Vehicle Transmission • 1. Transmission of disease by water, food, or air • 2. Transmission also possible by blood, and other body fluids

  23. Vectors • ARTHROPODS (Bugs) • Mechanical transmission: passive transport on insect’s feet or other body parts • Biological transmission – bite: infected insect can transmit the pathogen via a the bite route, example is malaria

  24. Nosocomial Infections(Hospital Acquired) • 5-6 infections per 100 admissions • 20,000 deaths per year • $4.5 billion dollars in costs per year • 80% of infections are caused by microbes “brought in” by patient • 20% of infections caused by microbes from the hospital

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