1 / 110

GENERAL PRINCIPLES OF INFECTIOUS DISEASES Department of Infectious Diseases, t he Third Affiliated Hospital Li Gang

GENERAL PRINCIPLES OF INFECTIOUS DISEASES Department of Infectious Diseases, t he Third Affiliated Hospital Li Gang ( 李刚） 2009.2.

micheal
Download Presentation

GENERAL PRINCIPLES OF INFECTIOUS DISEASES Department of Infectious Diseases, t he Third Affiliated Hospital Li Gang

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GENERAL PRINCIPLESOF INFECTIOUS DISEASESDepartment of Infectious Diseases, the Third Affiliated HospitalLi Gang (李刚）2009.2

  2. Introduction·Definition of infectious diseases and communicable diseases. · Distinction between infectious diseases and communicable diseases.

  3. Definition: 1. Infectious disease: any infection caused by microbes or parasites. 2. Communicable disease: infection transmitted from persons or animals to other persons.

  4. The goal of studying infectious disease:1. To study etiology, epidemiology, pathogenesis, clinical manifestations, treatment and prevention of infectious diseases. 2. To control and eliminate these diseases. (occurrence, spreading, prevention)

  5. Infection and immunity

  6. The concept of infection The course of struggle between pathogens and human or animal bodies (host).

  7. Pathogens:(microbes, parasites) Prion; virus; chlamydia; rickettsia; bacteria; fungus; spirochete. Protozoa; helminth.

  8. Emerging pathogens and infectious diseases 1977 Hantaan virus 1977 Ebola virus 1982 E coli O157：H7 1983 HIV 1986 CJD 1988 HEV 1989 HCV 1992 Vibrio cholerae O139 strain 1997 H5N1 2003 SARS coronavirus

  9. Three kinds of infection

  10. ⑴ Commensal infection: Pathogens live in the host but don’t induce pathologic changes.

  11. ⑵ Opportunistic infection:Pathogens within the host can induce pathologic changes if host immunity is suppressed by some factors.

  12. ⑶ Pathogenic infection: According to the severity of the pathologic changes, several degrees in clinical manifestation from mild, moderate to severe will occur.

  13. Infection status: Primary infection re-infection co-infection super infection secondary infection

  14. Manifestations of Infection Process

  15. Entrance and colonization of pathogens will lead to the following results.

  16. 1. Elimination: pathogens were excluded out by host nonspecific or specific immunity. Such as Candida albicans Escherichia coli

  17. 2. Covert (subclinical) infection:￭ Most frequently occurs in healthy individuals. ￭ The outcomes will be: A. Immunity acquired. B. Carrier state: healthy carriers.

  18. 3. Overt (clinical) infection: The outcomes will be: A. Recovery. B. Chronic carrier.

  19. 4. Carrier state: Definition of different types of carriers: . incubation carrier . acute carrier . convalescent carrier . chronic carrier

  20. 5. Latent infection: After infection, pathogens remain latent inside the body. Develop clinical manifestations when the host immunity has been impaired. Pathogens usually will not be excreted by the host during period of latency.

  21. The Role of Pathogens in the Infection Process:⑴ Invasiveness: adhesion, penetration ability. ⑵ Virulence: toxins, enzymes, and histolytic ability.⑶ Infection dose: minimal dose that can cause an infection.⑷Variability: change in structure of the pathogen to evade from host immunity.

  22. The Role of Immune Response in Infection Process:Differentiation between protective immunity and allergy. . Protective immunity: beneficial . Allergy(anaphylactic reaction): harmful

  23. ⑴ Nonspecific immunity:A. Natural barriers:external (skin, mucous membrane, cilia), internal (blood-brain barrier).B. Phagocytosis:macrophages, monocytes, and granulocytes.C. Humoral factors: complements, interferons, lysozyme, cytokines.

  24. ⑵ Specific immunity: Immune respond to specific recognizable antigens. A. Cell-mediated immunity: Important in intracellular infections by viruses, fungi, protozoa and certain bacteria.B. Humoral immunity: Different kinds of antibodies (immune globulins) and their functions.

  25. Pathogenic Mechanisms of Infectious DiseasesThe occurrence and natural course of infections can be divided into three stages:

  26. 1.Portal of entry:Each pathogen has its specific portal of entry.Such as: Mycobacterium tuberculosis, Meningococcus via breath tract. Shigella via digestive tract.

  27. 2. Localization and Dissemination in the host:Specific for each pathogen.Such as: . Mumps virus in parotid gland. . Hepatitis C virus in the liver. . Shigella in the intestine.

  28. 3. Channels of excretion: Important factor for host infectivity. As the source of infection. Such as: . Hepatitis A in the stool. . Hepatitis B in the blood. . Measles virus in expiratory air.

  29. Mechanism of Tissue Damages1. Direct invasion: Cytolysis, tissue necrosis, inflammation.2.The actions of toxins and cytokines: Resulting in septic shock, Disseminated intravascular coagulation, etc.

  30. Mechanism of Tissue Damages3. Immunopathogenesis: Immunosuppression, T-cell destruction, immune complexes, antibody-mediated cytotoxicities.

  31. Important Patho-physiologic Changes in infection

  32. 1. Fever(pyrexia): Exogenous and endogenous pyrogens.. Exogenous pyrogens: virus etc. . Endogenous pyrogens: IL-1, TNF, IL-6, interferon etc.

  33. 2. Metabolismchanges:(1) Protein: higher proteins catabolism. “acute” proteins (C-reactive protein, sign of acute inflammation). (2) Carbohydrate: acceleration of glucolysis.

  34. 2. Metabolismchanges:(3) Water and electrolytes: dehydration, hypokalemia.(4) Endocrine disturbances: higher anabolism, stress, hyper-corticosteroidemia.

  35. Epidemiological Process of Infectious Diseases and Influencing Factors

  36. Epidemiological Process (course): Definition: case occur, spread. The essential elements of epidemiological process include:

  37. 1. Sources of infection:Definition. Human, animal.⑴ Patients: acute, chronic; typical, atypical(mild, severe).⑵ Subclinical infection:no symptoms. poliomyelitis.⑶ Carriers:chronic, typhoid, shigellosis.⑷ Infected animals:(natural source)rabies, plague.

  38. 2. Routes of transmission⑴ Air, droplets, dusts. e.g. measles.⑵ Water, food, flies(fecal-oral infection).e.g. typhoid.⑶ Fingers, utensils(contact infection).e.g. shigellosis, influenza.

  39. ⑷ Arthropods.A. Biologic:intermediate hosts. e.g. mosquitoes in malaria, chiggers in scrub typhus. B. Mechanical:passive transfer. e.g. flies in amebiasis.

  40. 3. Population susceptibility: Proportion of susceptibles.

  41. Factors Influencing Epidemiological Process

  42. 1. Natural factors:Climatic and geographic factors.. Climatic: season, rain, humidity.. Geographic: endemicity.

  43. 2. Social factors: social system, social-economic condition, cultural background.

  44. Characteristics of Infectious Diseases

  45. Basic characteristics:(1) Pathogens.(2) Infectivity. (3) Epidemiological features: age, sex, season; imported or endemic; sporadic, epidemic, pandemic, outbreaks.(4) Post-infection immunity.

  46. 2. Clinical Characteristics:(1) Development stage:A.Incubation period.B.Prodromal period.C.Symptomatic period. Apparent clinical manifestations.D.Convalescent period.E. Recrudescence or relapse.F.Sequelae.

  47. 2. Common symptoms and signs.

  48. ⑴ Fever(pyrexia) :Courses:A. Effervescence: early stage. B. Fastigium: full-blown stage.C. Defervescence: improvement stage

  49. Forms:A. Sustained fever:Difference of body temperature less than 1℃ within 24 hours, over 39℃. e.g. Second week of typhoid.

  50. 1 2 3 4 5 6 7

More Related