Structure of the epidemiological process

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Structure of the epidemiological process

  1. 1. BASIC PRINCIPLES IN THE FIGHT AGAINST INFECTIOUS DISEASES. PROPHYLACTIC AND ANTIEPIDEMIC MEASURES Prof. Dr. N. Ribarova, MD
  2. 2. <ul><li>STRUCTURE OF THE EPIDEMIOLOGICAL PROCESS </li></ul><ul><li>Source of infection </li></ul><ul><li>Mechanism of transmission </li></ul><ul><li>Susceptibility of the </li></ul><ul><li>Population </li></ul>
  3. 3. <ul><li>Changes in these factors caused by the social and natural environment reflect on the intensity of the epidemic process. </li></ul>
  4. 4. <ul><li>Thus the efficacious prophylactics and effective fight against infectious diseases are possible only when the antiepidemic measures are directed in three ways: </li></ul><ul><li>measures eliminating or decontaminating the source of infection; </li></ul><ul><li>measures stopping the mechanism of transmission of infection; </li></ul><ul><li>measures stimulating insusceptibility of the population to a certain disease. </li></ul>
  5. 5. <ul><li>I. MEASURES ELIMINATING OR DECONTAMINATING THE SOURCE OF INFECTION </li></ul><ul><li>It is the main trend in the fight against infectious diseases. </li></ul><ul><li>* measures for extermination - elimination of the sick animals (carriers of infection). The method is the best one in case of infected wild animals as well as domestic animals; </li></ul><ul><li>* measures for derattization - used at rodents, reservoirs of infections; </li></ul><ul><li>* sanitary measures - concerning domestic and farm animals (for example, carriers of brusellosis). In this way animals are used for the purposes of the farms simultaneously with the measures for their recovery. </li></ul>
  6. 6. <ul><li>Measures for extermination are not applicable at anthroponosus infectious diseases where the source of infection is the man - a sick person or a carrier of infection. In this case the aim is to decontaminate the source of infection putting it in such conditions in which the possibilities for transmission of infection are cut off. </li></ul><ul><li>*isolation of the sick persons - in an infectious ward or at home. Complete influencing of the source of infection is impeded also by the characteristics of the clinical course of the disease - inapparent, mild clinical forms, chronic forms, etc. </li></ul>
  7. 7. <ul><li>Localization and decontamination of the source of infection depend on: </li></ul><ul><li>* living conditions - conditions facilitating transmission of infection to other persons should be eliminated; </li></ul><ul><li>* attitudes of the population - whether people seek doctors' help immediately, refusal of hospitali-zation, etc. as well as degree of health knowledge and responsibility for the economic costs. </li></ul><ul><li>* possibilities for specific, etiologic treatment of the sick persons and carriers of infection. </li></ul>
  8. 8. <ul><li>Urgent prevention is also one of the measures for influencing the source of infection. Urgent prevention - it is the use of prophylactic and curative means to prevent development of the disease from the carriers of infection in incubation. For this purpose immune serums, vaccines, bioproducts, chemotherapeutic agents – sulfonamides, antibiotics, etc. are applied. </li></ul>
  9. 9. <ul><li>II. MEASURES STOPPING THE MECHANISM OF TRANS-MISSION OF INFECTION </li></ul><ul><li>These measures are various ones. They are mainly related to the specific characteristics of the mechanism of transmission of the different infectious diseases. Generally, it is very difficult to carry out such measures. </li></ul>
  10. 10. <ul><li>1. Diseases belonging to the group of enteric infections. </li></ul><ul><li>The measures require the agents of infection in the faeces of the sick persons not to get through food, water, etc. into the gastrointestinal tract of the healthy people. </li></ul>
  11. 11. <ul><li>Sanitary measures eliminating the faecal-oral way of infection are of crucial importance: </li></ul><ul><li>development and urbanization of the built-up areas; </li></ul><ul><li>water supply, sewerage; </li></ul><ul><li>decontamination of the sewerage waters; </li></ul><ul><li>collection and decontamination of the hard wastes; </li></ul><ul><li>sanitary measures in public catering; </li></ul><ul><li>following the regulations of sanitation; </li></ul><ul><li>school hygiene; </li></ul><ul><li>health knowledge of the population. </li></ul>
  12. 12. <ul><li>2. Diseases belonging to the group of respiratory infections: </li></ul><ul><li>Gauze masks, aeration and ventilation, bactericidical lamps, disinfection. </li></ul>
  13. 13. <ul><li>3. Diseases belonging to the group of blood infections: </li></ul><ul><li>Character, access and effectiveness of the measures applied depend on the biological carrier: </li></ul><ul><li>agromeliorative measures; </li></ul><ul><li>hydrotechnical measures; </li></ul><ul><li>disinsection and derattization; </li></ul><ul><li>means of individual prevention; </li></ul><ul><li>stimulating accumulation of health knowledge. </li></ul>
  14. 14. <ul><li>4. Diseases belonging to the group of covering infections: </li></ul><ul><li>They are transmitted through the personal belongings, household goods, etc. </li></ul><ul><li>* disinfection; </li></ul><ul><li>* hygienic measures for decontamination; </li></ul><ul><li>* stimulating the accumulation of health knowledge of the population. </li></ul>
  15. 15. <ul><li>III. MEASURES STIMULATING INSUSCEPTIBILITY OF THE POPULATION </li></ul><ul><li>A perspective for prevention and fight against infectious diseases is development of specific insusceptibility of the population to infectious diseases. </li></ul>
  16. 16. <ul><li>IMMUNITY represents a complex of preventive physiologic responses of the whole organism, i.e. it is a way of prevention of the organism from protein bodies carrying themselves foreign gene information. </li></ul>
  17. 17. <ul><li>Immune system recognizes the relevant antigens through its immunocompetent cells and reacts against them producing IMMUNE RESPONSE as well as developing immune memory and immune tolerability. </li></ul>
  18. 18. <ul><li>IMMUNE RESPONSE is a complex reaction of the organism induced by the antigen penetrated in it, which morphologic base is proliferation and differentiation of the immunocompetent cells. </li></ul>
  19. 19. <ul><li>Recognition of the antigen is made with the help of two types of lymphocytes: </li></ul><ul><li>* T-lymphocytes - they have developed their immunologic competence through thymus and that is why they are called &quot;thymus-dependent&quot;; </li></ul><ul><li>* B-lymphocytes - they have developed their immunologic competence through the 'Fabricius bursa&quot; (for the birds) or through its equivalent for the mammals, probably bone marrow or part of the lymph tissue of the intestines - 'Payer's plaques', appendix and tonsils. </li></ul>
  20. 20. <ul><li>In the course of the evolution the following types of immunity have been developed: </li></ul><ul><li>1. Hereditary (species) immunity: </li></ul><ul><li>It is formed during the philogenetic development of the individual. It represents a state of insusceptibility of the organism related to the species to which the man or the animal belong. It is inherited (for example, people do not suffer from hen cholera, animals - from measles). </li></ul>
  21. 21. <ul><li>2. Acquired (individual) immunity. </li></ul><ul><li>It is formed during the ontogenetic development of the individual. The ability of the organism to develop ontogenetic mechanisms is a result from its philogenesis. Individual immunity is divided as follows: </li></ul><ul><li>A. Naturally acquired immunity, which, on its part, is </li></ul><ul><li>divided to: </li></ul><ul><li>* passive - due to antibodies, inherited from the mother; </li></ul><ul><li>* active – postinfectious, domestic immunity. </li></ul><ul><li>B. Non-naturally acquired (pos-timmunization) </li></ul><ul><li>immunity, divided to: </li></ul><ul><li>*active - developed after application of vaccines and </li></ul><ul><li>toxoids; </li></ul><ul><li>*passive - after administration of readymade antibodies </li></ul><ul><li>through serums and immunoglobulins. </li></ul>
  22. 22. <ul><li>The difference between these two types of development of immunity is related to the way of development as well as the level of its intensity and duration. </li></ul>
  23. 23. <ul><li>According to the mechanism of development of the immune response immunity is divided as follows: </li></ul><ul><li>• humoral immunity - it acts thro-ugh B-lymphocytes as well as antibo-dies circulating freely as immunoglobulins in the blood and the other body liquids. The antibodies react directly to the antigens forming a type of response &quot;antigen-antibody&quot; - precipitation, neutralization, accumulation,etc. depending on its conditions. </li></ul><ul><li>• cell immunity - it acts through the circulating T-lymphocytes together with the non-immunoglobulin mediators of the lymph function (activated macrophages). </li></ul><ul><li>Local immunity is an antigen (mainly IgA) and is cell mediated - in the immunosecretory system of the mucous of the gastrointestinal tract and respiratory ways (the entrance of infection). </li></ul>
  24. 24. <ul><li>Collective immunity - it is the ability of the human collective to resist to the activity of the agents of the infectious diseases and to prevalence of the endemic process. It is determined by the specific immune structure of the population as well as the possibility for realization of the mechanism of transmission of infection in the real circumstances. </li></ul>
  25. 25. <ul><li>Immune structure is a concept reflecting the distribution of the members of the group depending on the degree of their susceptibility to infectious diseases. </li></ul>
  26. 26. <ul><li>Non-specific immunologic structure - it characterizes the degree of insusceptibility of the population to all infectious diseases. It is measured by different immunologic, physiologic, and other methods. </li></ul>
  27. 27. <ul><li>Specific immunologic structure - it characterizes insusceptibility of the population to a certain infectious disease. It is measured by the percentage of the individuals possessing immunity. </li></ul>
  28. 28. <ul><li>Collective immunity is not a simple sum of the individual immunity of the separate members of the group. Different individuals may belong to the group as follows: </li></ul><ul><li>with highly intensive immunity; </li></ul><ul><li>with partial immunity; </li></ul><ul><li>with out developed immunity. </li></ul>
  29. 29. <ul><li>There are many different contingents of susceptible individuals: </li></ul><ul><li>newborns and toddlers (due to undeveloped immune system); </li></ul><ul><li>recovered individuals with short-term and slightly intensive immunity; </li></ul><ul><li>individuals immigrating to regions, which are endemic for certain diseases; </li></ul><ul><li>old-aged individuals (with reduced resistance of the organism); </li></ul><ul><li>individuals suffering from innate and acquired impairments of the immune system, ofimmunogenesis, etc. </li></ul>
  30. 30. <ul><li>Characteristics of the three directions of prevention and fight against infectious diseases provide the possibility for achieving the necessary practical results at many infectious diseases if the measures influencing the preventive directions are simultaneously carried out – decontamination of the source of infection, stopping the mechanism of transmission of infection and stimulating the specific insusceptibility of the population. This is the basic principle of the antiepidemic fight. </li></ul>
  31. 31. <ul><li>One of these three ways of activity is the basic one as the other two are complementary depending on the nature of the infectious disease and the situation. </li></ul>
  32. 32. <ul><li>ANTIEPIDEMIC MEASURES IN THE EPIDEMIC CENTRE </li></ul><ul><li>I. Measures to the patient </li></ul><ul><li>1. Early finding and recognition of the disease. </li></ul><ul><li>2. Putting proper diagnosis. </li></ul><ul><li>clinical methods; </li></ul><ul><li>laboratory methods; </li></ul><ul><li>epidemiological methods. </li></ul><ul><li>3. Registration and informing for the infectious disease. </li></ul><ul><li>quick informing - form N 58; </li></ul><ul><li>Registration book of infectious diseases - form N 60; </li></ul><ul><li>Registration book of hospital infections - form N 11. </li></ul>
  33. 33. <ul><li>4. Isolation of the patient in an infectious ward or at home: </li></ul><ul><li>transportation of the patient - in a suitable way for him/her; safe for the other persons; </li></ul><ul><li>sanitary manipulation - bathing, decontamination of the clothes and underwear, eliminating parasites; </li></ul><ul><li>specific etiologic therapy; </li></ul><ul><li>dehospitalization of the patient: </li></ul><ul><li>* after full clinical recovery </li></ul><ul><li>* elimination of the pathogenic agent (the infect) </li></ul><ul><li>* sanitary manipulation; </li></ul><ul><li>* disinfection of the clothes, underwear, etc. Chronically sick patients are under dispensary observation. </li></ul>
  34. 34. <ul><li>II. Measures to the other persons (contacting ones as well as carriers of infection) </li></ul><ul><li>1. Measures to contacting persons: </li></ul><ul><li>epidemiological investigation for finding of all contacting persons; </li></ul><ul><li>registration - &quot;Book for persons in contacts with acutely infected patients&quot; - form N 61; </li></ul><ul><li>medical observation - a maximal incubation period, thermometring, clinical examination; </li></ul>
  35. 35. <ul><li>sanitary manipulation - when necessary; </li></ul><ul><li>quarantine of the contacting persons - highly infected ones in isolation - serologic, microbiological, virusologic analyses; </li></ul><ul><li>active or passive immunization; </li></ul><ul><li>urgent prevention with antibiotics and chemotherapeutical agents. </li></ul>
  36. 36. <ul><li>2. Measures to the carriers of infection: </li></ul><ul><li>finding - epidemiological investigation; </li></ul><ul><ul><li> - microbiological investigation; </li></ul></ul><ul><li>sanation of the carriers of infection - directed to elimination and cleaning of the pathogenic micro-organisms; </li></ul><ul><li>isolation. </li></ul>
  37. 37. <ul><li>SPECIFIC PREVENTION </li></ul><ul><li>Definition: An approach for development of non-natural specific insusceptibility to the etiologic agent of a certain infectious disease. </li></ul>
  38. 38. <ul><li>Vaccination process: An interaction between the vaccine agent and the human organism with its individual characteristics. It is a complex reaction, which includes as follows: </li></ul><ul><li>specific immune reorganization resulting in development of immunity (the aim of the immunization); </li></ul><ul><li>concomitant processes of non-specific reorganization (directed to restoration of the homeostasis) as well as allergization, clinically manifested or asymptomatic. </li></ul>
  39. 39. <ul><li>Different preparations are used for development of immunity - vaccines, toxoids, serums, immunoglobulins. </li></ul>
  40. 40. <ul><li>Live vaccines: Immune preparations, containing bacteria and viruses that have lost their pathogenic properties but preserved their immunologic properties. Such types of vaccines are as follows: against tuberculosis, polyomielitis, measles, mumps, influenza, smallpox, tularemia, brucellosis, anthrax, plaque, yellow fever, etc. These vaccines develop intensive and longterm immunity. </li></ul>
  41. 41. <ul><li>Inactivated vaccines: They are prepared from the cultures of different infects, inactivated physically (heating up) or chemically (formalin, phenol, alcohol, etc.) - abdominal typhus, paratyphus, cholera, who - oping-cough, leptospyroses, etc. as their immunogenic properties are preserved. </li></ul><ul><li>Recombinant vaccines: They are made with the help of gene engineering with hybridoma technic, etc. </li></ul>
  42. 42. <ul><li>Chemical vaccines: They are full antigen vaccines, derived chemically from bacterial cultures. </li></ul><ul><li>They are maximally lacking ballast substances, side protein components and cause relatively low allergization of the organism. They are stable. (Against enteric infections – abdominal typhus, paratyphus A and B, together with a tetanicus toxoid). </li></ul><ul><li>Toxoids: They are derived from the products of the microorganisms, mainly their toxins, through their inactivation (by formalin or heating up) - against diphtheria, tetanus, staphylococcus infection, etc. </li></ul>
  43. 43. <ul><li>Protective antigens: Immunization substances related to the pathogenic factors of bacterial and virus cells. Such antigens are discovered lately in plaque and whooping-cough bacteria, streptococcus, staphylococcus, anthrax bacilli, Ricketsias, etc. </li></ul>
  44. 44. <ul><li>Serums: Immune preparations proving passive immunologic prevention for a short time (2 to 4 </li></ul><ul><li>weeks). They are ready-made antibodies (anthrax, whooping-cough, epidemic meningitis, tetanus, diphtheria, botulism, staphylococcus infection). </li></ul><ul><li>Bacteriophages: live agents, which are parasites in the bacterial cell - abdominal typhus, shigelloses, salmonelloses, cholera. They have limited application. </li></ul>
  45. 45. <ul><li>Interferon: a protein synthesized from the cells in response to a virus infection making the other cells resistant to infection. It inhibits virus proliferation through non-immunologic mechanisms (virus interference) - application at influenza, parainfluenza, coxsackie B3, ECHO-13, adenoviruses, enteric infections, etc. </li></ul><ul><li>Immunoglobulins: simple, hyperimmune. </li></ul>
  46. 46. <ul><li>Application of vaccines: </li></ul><ul><ul><li>* subcutaneous, intracutaneous, oncutaneous, </li></ul></ul><ul><ul><li>peroral, intranasal, aerosol method. </li></ul></ul><ul><li>Application of serums and inimunoglobulins: </li></ul><ul><li>* subcutaneous, intracutaneous (strictly </li></ul><ul><li>according to the method of Bezredka). </li></ul>
  47. 47. <ul><li>Postimmunization reactions of the organism : </li></ul><ul><li>general - changes in the body temperature and state of the organism; </li></ul><ul><li>local - hyperemia and edema. </li></ul><ul><li>Postimmunization complications: </li></ul><ul><li>serum disease, anaphylactic shock, postvaccination encephalitis, etc. </li></ul>
  48. 48. <ul><li>Contraindications : </li></ul><ul><li>severe states of the organism: acute infectious diseases, active form of tuberculosis, decompensated valvular disease, hypertension, renal diseases (nephritis), diabetes, broncl asthma, anemia, cachexia, the second half of pregnancy, etc. </li></ul><ul><li>specific for the disease. </li></ul>
  49. 49. <ul><li>The effect of immunizations depends on: </li></ul><ul><li>compatibility of the immunizations; </li></ul><ul><li>the scheme and dosage of the vaccines; </li></ul><ul><li>reactivity of the organism; </li></ul><ul><li>size of the immune layer. </li></ul>
  50. 50. <ul><li>Organization of application of immunizations: </li></ul><ul><li>bioproducts supply; </li></ul><ul><li>quality of the bioproducts; </li></ul><ul><li>storage conditions and transportation of the bioproducts. </li></ul>
  51. 51. <ul><li>Immunization calendar: importance. </li></ul><ul><li>Inspection of the results of the immuniztions. </li></ul><ul><li>Registrations, reporting, collective immunity. </li></ul>
  52. 52. <ul><li>Possibilities for application of the vaccines: </li></ul><ul><li>according to the aims of prevention; </li></ul><ul><li>according to epidemiological indications. </li></ul><ul><li>Immune prevention with serums: when necessary. </li></ul>
  53. 53. <ul><li>DISINFECTION </li></ul><ul><li>1. Generally, disinfection (decontamination) is a complex of methods and means directed to elimination of the source of infection in the environment. The concept includes the following stages: disinfection itself together with sterilization and antiseptic method, disinsection and derattization. </li></ul>
  54. 54. <ul><li>DISINFECTION (itself) means the elimination of the pathogenic microorganisms in the environment </li></ul>
  55. 55. <ul><li>Types of disinfection according to its goals and tasks are as follows: </li></ul><ul><li>Prophylactic (preventive) disinfection: </li></ul><ul><li>It is carried out where a centre of infection does not exist but there are facilitating conditions of its development. It is performed systemically under plans for certain periods of time - in nursery schools, schools, hospitals, cinemas, theatres, railway stations, catering establishments, of drinking water, milk, food, etc. </li></ul>
  56. 56. <ul><li>Disinfection of the centre of infection. It is carried out in the centre of infection. Its aim is the elimination of the pathogenic mechanisms in the environment of the patient producing the microorganisms and contaminating the environment. Disinfection performed during the course of the disease is called current disinfection . After recovery of the patient , its hospitalization or after a lethal outcome the final (ending) disinfection is performed . The quality of the current disinfection determines the complex of tasks, methods and means for the final disinfection. </li></ul>
  57. 57. <ul><li>STERILIZATION. A method for elimination of all microorganisms (pathogenic and saprophyte, viruses, bacteria, mould) in their different forms - vegetative and spores </li></ul>
  58. 58. <ul><li>SANITATION. A method for the rapid reduction of the microbial flora in an object in the environment (for example, after washing). It is widely applied in everyday life as a preventive measure. </li></ul>
  59. 59. <ul><li>ANTISEPTIC METHOD. A method for prevention of development of microorganisms on the human skin and mucous. </li></ul>
  60. 60. <ul><li>DISINSECTION: elimination of the arthropods, carriers of infectious diseases. </li></ul><ul><li>DERATTIZATION: elimination of the rodents, natural reservoirs of infections. </li></ul>
  61. 61. <ul><li>Methods of disinfection: </li></ul><ul><li>Biologic method: biological filters for decontamination of the water (on the base of the microbial antagonism). </li></ul><ul><li>Mechanical m ethod : cleaning, wash ect. </li></ul><ul><li>Physical method: sun shining, ultra-violet rays, ionizing radiation, supersound, dry heat for sterilization by dry air, wet heat – sterilization and vapour under pressure. </li></ul><ul><li>Chemical method: use of chemical compounds-disinfectants. </li></ul>
  62. 62. <ul><li>Methods of disinsection: </li></ul><ul><li>Biological method: use of the natural enemies of the harm arthropods - predatory animals (the fish gambusia), parasites, pathogenic microorganisms (Bacillus thuringiensis), genetically changed, sexually sterile populations. </li></ul><ul><li>Mechanical method: cleaning, wash, etc. </li></ul><ul><li>Physical method: high temperature - hot dry and wet air for vapouring, sterilization, burning out, etc. </li></ul>
  63. 63. <ul><li>5. Chemical method: insecticides: </li></ul><ul><li>larvacides - for elimination of larvae; </li></ul><ul><li>acaricides - for elimination of Acars; </li></ul><ul><li>ovocides - for elimination of their eggs; </li></ul><ul><li>pesticides - for elimination of weeds; </li></ul><ul><li>* attractants - attracting insects; </li></ul><ul><li>* repellents - repelling insects. </li></ul>
  64. 64. <ul><li>Insecticides for arthropods depending on their way of penetration in the organism are as follows: </li></ul><ul><li>fumigants - gas insecticides - they act through the respiratory system; </li></ul><ul><li>intestinal insecticides - through the digestive tract; </li></ul><ul><li>contact insecticides - act at contact to outer parts of the insects: </li></ul><ul><li>a) with residual effect; </li></ul><ul><li>b) without residual effect. </li></ul>
  65. 65. <ul><li>Methods of derattization: </li></ul><ul><li>1.Preventive (prophylactic) derattization: </li></ul><ul><li>a) sanitary and technical means – lack of access of </li></ul><ul><li>the rodents to the buildings – openings of drainage, </li></ul><ul><li>doorstills, etc. </li></ul><ul><li>b) sanitary and hygienic measures – lack of access to </li></ul><ul><li>food. </li></ul><ul><li>Exterminatory derattization: </li></ul><ul><li>a) biologic method – natural killers of the rodents. </li></ul><ul><li>b) mechanical method – use of traps; </li></ul><ul><li>c) chemical method – use of chemical compounds – </li></ul><ul><li>rodenticides. </li></ul>

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