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Infectious Disease

Infectious Disease. Infectious Disease. Globally, Infectious disease is still the single most common cause of death in 1993, >16 million people died from infectious diseases Many diseases, previously considered conquered, have once again re-emerged Tuberculosis pneumonia

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Infectious Disease

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  1. Infectious Disease

  2. Infectious Disease • Globally, Infectious disease is still the single most common cause of death • in 1993, >16 million people died from infectious diseases • Many diseases, previously considered conquered, have once again re-emerged • Tuberculosis • pneumonia • food-borne illnesses

  3. Reemerging Infectious Disease

  4. Reemerging Infectious Disease • Why? • Human Demographics and Behavior • Technology and Industry • Economic development and Land Use • Microbial Adaptation and Change • Breakdown of Public Health Measures • and Deficiencies in Public Health • Infrastructure

  5. Communicable infection - a disease that is transmitted from person to person (NOT necessarily spread by direct contact!) influenza HIV tuberculosis chicken pox Noncommunicable infection - a disease that is not directly transmitted from person to person malaria botulism Rabies What is an Infectious disease?

  6. Cryptosporidiosis (protozoan) Diphtheria (bacterium) Malaria (protozoan) Meningitis, necrotizing fasciitis (flesh-eating disease), toxic-shock syndrome, and other diseases Group A Streptococcus (bacterium) Pertussis (whooping cough) (bacterium) Reemerging

  7. Reemerging • Rubeola (measles)(virus) • Schistosomiasis (helminth) • Rabies (virus) • Tuberculosis (bacterium) stricken) • Yellow fever (virus)

  8. What causes infectious diseases? • Microorganisms • Bacteria • Virus • Prion • Fungus • Protozoa • Helminth • Products from microorganisms • toxins

  9. Just how big are these guys anyway? Bar is 10 microns • viruses • 0.05 to 0.1 microns • bacteria • 0.5 to 1.5 microns • red blood cell • 5 microns • lymphocyte (white blood cell) • 5 to 8 microns • human sperm • 60 microns

  10. Some Definitions • Infectivity- capacity of an agent to enter & replicate within a susceptible host • Pathogenicity - capacity of an agent to cause clinical signs (disease) in a host • Virulence - refers to the severity of disease • Clinical disease - patient has noticeable symptoms of illness • Subclinical disease - no apparent symptoms; if infection persists, patient is known as a carrier

  11. Modes of Transmission

  12. Why do people get sick? • Agent Factors • new pathogens (HIV, Nile-like virus) • changes in pathogens (acquire antibiotic resistant genes) • Environmental Factors • changes in environmental conditions (el niño) • new environments (natural or man-made) • (Sweetwater wetlands)

  13. Why do people get sick?, contd. • Host Factors • age • gender • ethnicity • immune status • nutritional status • behavior • Balance is Key!

  14. Are all bacteria bad? • No! • Some bacteria perform essential functions in the body such as: • skin: prevents more harmful bacteria from colonizing • intestines: helps body break down and absorb certain nutrients; prevents more harmful bacteria from causing intestinal infections • vagina: prevents yeasts from overgrowing and causing infections • Other body areas are colonized and infections only occur in immunocompromised people • nasopharynx, oropharynx, esophagus, stomach

  15. Prevention and Treatment • Sanitation • water and waste treatment • personal hygiene • Vaccination • probably the #1 way to prevent communicable diseases • Healthy living (avoidance) • practice safe sex • avoid IV drugs • avoid hospital stays (5% of patients acquire a nosocomial infection) • Antibiotics and other drugs • use wisely and sparingly • don’t use antibiotics for viral infections

  16. Antibiotics • Penicillin • discovered in 1940s • natural product of bread mold • thought to be the miracle cure for all infections • now many organisms are resistant • Antibiotic Resistance • antibiotics do not work on viral infections • inappropriate use and overuse has resulted in many antibiotic resistant organisms (some organisms can transfer resistance between species) • research into new antibiotics has fallen behind • many multiply resistant organisms exist

  17. Your Immune System • Part of the lymphatic system • Primary lymphoid organs • bone marrow • spleen • lymph nodes • thymus • Secondary lymphoid organs • Peyer’s patches • tonsils • appendix • mucosal associated lymphoid tissues (MALT)

  18. Immunity

  19. Cells of the Immune System • Leukocytes (white blood cells) • neutrophils (PMN’s) • monocyte/macrophage • eosinophil • basophil • Specialized cells • B-cells antibodies • T-cells

  20. Innate immunity • First-line defenses • skin • low pH, low moisture, normal desquamation, antibacterial substances • vaginal epithelium • low pH, normal flora, • conjunctival epithelium • flushing effects of tears, lysozyme, lactoferrin • respiratory epithelium • secretory IgA (sIgA), lysozyme, lactoferrin, mucociliary escalator • gastrointestinal epithelium • hydrochloric acid, gastric enzymes,mucus,sIgA, normal flora • urinary epithelium • flushing effects of urine

  21. Innate immunity • Second-line defenses (occurs after organism breaches epithelial layer) • Initial environment • tissue fluids: lysozyme, lactoferrin • monocyte/macrophage: engulf & destroy • NK cells: recognize altered self cells • lymphatic fluid: drains tissues to lymph nodes

  22. Innate immunity • Second-line defenses, cont’d. • Inflammation - normal host response to a traumatic or infectious injury • heat • pain • redness • swelling • loss of function

  23. Innate immunity • Second-line defenses, cont’d. • Phagocytic defenses (by order of appearance) • PMN’s -polymorphonuclear leukocytes (neutrophils) • monocytes (in blood) • macrophages (in tissue)

  24. Adaptive Immunity • Cell-mediated • T-cells(CD4, CD8) • Humoral • B-cells • antibodies (immunoglobulins: IgM, IgG, IgA, IgE, IgD) • Both • complement cascade

  25. Autoimmune Diseases • Immune system fails to differentiate between self and non-self and generates antibodies against self proteins • lupus - immune cells attack DNA • arthritis - immune cells attack cartilage and bone • multiple sclerosis - immune cells attack central nervous system

  26. Prevention

  27. Epidemiology

  28. Initial case investigation- looking at reported cases of interest There are three questions to consider: • Who? • Where? • When?

  29. Who? • Gender • Age • Occupation • Cultural background • Signs and symptoms

  30. Where? • Physical location • Open or enclosed • High or low

  31. When? • Time of day • Time of Week • Time of month and year • Duration of event • Sequence of events

  32. Epidemiological Guidelines 1. Investigate reported cases

  33. 2. Form a Hypothesis

  34. 3. Come up with a working case definition

  35. 4. Design a questionnaire

  36. 5. Apply questionnaire to cases and controls

  37. 6. Refine case definition, refine hypothesis • Identify similarities • Assemble identified case reports • Exclude disqualified reports • Test hypothesis against identified cases

  38. Take Action

  39. 8. Communicate Findings

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