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Infectious disease in epidemology.pptx

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Infectious disease in epidemology.pptx

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this power point slide consists the important points regarding to infectious diseases control, helps for medical students as well as clinicians to add some values on their level of awareness regarding to communicable diseases.

this power point slide consists the important points regarding to infectious diseases control, helps for medical students as well as clinicians to add some values on their level of awareness regarding to communicable diseases.

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Infectious disease in epidemology.pptx

  1. 1. JIGJIGA UNIVERSITY COLLEGE OF M&HS DEPARTMENT OF NURSING COMMUNICABLE DISEASES CONTROLE GIRUM.S(MSC, MPH) November, 2022
  2. 2. Communicable diseases control Definition of common terms in ID. Definition of infectious disease. Features of infectious diseases.  Chain of disease transmissions.  Types of carriers and disease transmission role. Time Course of Infectious Diseases. Mode of transmission Level of diseases prevention Principles(strategies) of communicable disease control 12/8/2022 2
  3. 3. Definition common terms Epidemics -occurrence of disease in excess of what is expected in a limited period.  Endemic - a disease that is usually present in a population or in an area at a more or less stable level.  Sporadic - a disease that does not occur in that population, except at occasional and irregular intervals  Outbreak:- Epidemic of;- shorter duration covering a more limited area affecting small proportion of populations. 12/8/2022 3
  4. 4. Cont…..  Pandemic - an epidemic spread over several countries or continents, affecting a large number of people.  Disease - a state of physiological or psychological dysfunction.  Infection - the entry and development or multiplication of an infectious agent in the body of man or animal.  Infestation:- presence of living infectious agent on the exterior surface of the body.(Arthropods, rodents) 12/8/2022 4
  5. 5. Definition of common terms….  Infectious:- caused by microbes and can be transmitted to other persons Infectious agent:- an agent capable of causing infection Infectivity:- the proportion of exposed persons who become infected. Pathogenicity:- the proportion of infected persons who develop clinical disease.  Virulence:- the proportion of persons with clinical disease who become severely ill or die.  Contamination:- the soiling or pollution of inanimate objects or living material with ;- harmful,or potentially infectious or other unwanted materials. 12/8/2022 5
  6. 6. 12/8/2022 6
  7. 7. Definition of communicable diseases  These are illnesses due to specific infectious agents or its toxic products, which arise through;- Transmission of that agent, or Its toxic products from;-  An infected person,  Animal or inanimate reservoir to a susceptible host, either directly or indirectly. 12/8/2022 7
  8. 8. Infectious diseases  Unique features of communicable disease: The cause is known(An infectious agent is a necessary cause)  A case is a risk factor:- Infection in one person can be transmitted to others Carriers as a source of infection  People may be immuned (herd immunity) i.e measles Usually their is a need for urgency Preventable measures are effective Mostly curable 12/8/2022 8
  9. 9. Natural history of infectious disease • It refers to the progression of a disease process in an individual over time, in the absence of treatment. • stages: exposure, infection, infectious disease, and outcome • Understanding the natural history of a disease is • an important prerequisite for designing studies that assess the impact of interventions, • both chemotherapeutic and environmental, on the initiation and expression of the condition • For example, untreated infection with HIV causes a spectrum of clinical problems beginning at • the time of seroconversion (primary HIV) and • terminating with AIDS and usually death. 12/8/2022 9
  10. 10. Natural history cont….. 12/8/2022 10
  11. 11. Classification of infectious diseases • Based on infectious agent Bacterial Fungal Viral Protozoan • Based on pattern of occurrence Nosocomial infections Community acquired infections 12/8/2022 11
  12. 12. Cont… • Based on clinical manifestation Diarrheal diseases (cholera, shigellosis...) Febrile illness (malaria, typhoid...) Respiratory disease(Pneumonia, tuberculosis...) UTI infections (Upper and lower UTI) CNS infection(meningitis ,encephalitis) 12/8/2022 12
  13. 13. Classification Cont…..  Epidemiological classification/based on modes of disease transmission: Food borne disease Water borne disease Airborne disease Vector borne disease 12/8/2022 13
  14. 14. MODES OF TRANSMISSION 1. Direct Transmission  Skin to Skin.  Mucosa to Mucosa.  Mucosa to Skin, of the same person or different Person. Eg:- STD, AIDS, skin and eye infections.  Droplet Infection:- Direct Projection of a spray of droplets of saliva and naso-pharyngeal secretions during • coughing, sneezing or speaking to the surrounding atmosphere. Eg: Respiratory infections, diphtheria, whooping cough, TB, Meningococcal meningitis 12/8/2022 14
  15. 15. 12/8/2022 15 Droplet Sprayed into the Air from a Sneeze
  16. 16. DIRECT TRANSMISSION…CONT..  Contact with Soil Eg: Hookworm larva, Tetanus  Inoculation into skin or mucosa Eg: Rabies, infected needles  Trans-placental (vertical) Eg: TORCH agents, syphilis, HBV, AIDS 12/8/2022 16
  17. 17. 2. INDIRECT TRANSMISSION Traditionally 5F’s Flies Finger Fomites Food Fluids 12/8/2022 17
  18. 18. INDIRECT TRANSMISSION…CONT  Vehicle-borne.  Water  Food  Blood, Serum, Plasma  Tissues and organs Vector-born Air-borne. Fomite-borne:- Inanimate article or substances other than water or food contaminated by infectious agents  Unclean hand and finger 12/8/2022 18
  19. 19. Chain of disease transmission  There are six successive events implicated in the chain of disease transmission. Components of Chain of Infection 1. Causative Agent 2. Reservoir host 3. Portal of exit 4. Mode of transmission 5. Portal of entry 6. Susceptible host 12/8/2022 19
  20. 20. Components of Chain of Infection 12/8/2022 Susceptible host Neonates Diabetics Immuno-suppression Cardiopulmonary disease Elderly Infectious agent Bacteria Fungi Viruses Protozoa Reservoir People Equipment Water Portal of exit Excretions Secretions Droplets Skin contact Means of transmission Bloodborne Airborne Droplet Common vehicle Vectorborne 20
  21. 21. Cont…. 1. Infectious agent An organism that is capable of producing infection or infectious disease 2. Reservoir of infection • Which is an infectious agent normally lives and multiplies, on which it depends primarily for survival and where it reproduces itself Types of reservoirs  Man  Pathogens that are specifically adapted to man, (measles, typhoid, meningococcal meningitis, gonorrhea and syphilis)  Animals Some infective agents that affect man have their reservoir in animals The term “zoonosis” is applied to disease transmission from animals to man under natural conditions (Bovine TB, Brucellosis, Anthrax, Rabies) 12/8/2022 21
  22. 22. Cont…. • Non-living things as reservoir  Many of the agents are basically saprophytes living in soil and fully adapted to live freely in nature  C. botulinum etiologic agent of Botulism  C. tetani etiologic agent of Tetanus  C. welchi etiologic agent of gas gangrene 12/8/2022 22
  23. 23. Cont…. 3. Portal of exit (mode of escape from the reservoir): This is the site through which the agent escapes from the reservoir. Examples include: • GIT: typhoid, fever, bacillarydysentery, amoebic dysentery, cholera, ascariasis, etc. • Respiratory: tuberculosis, common cold, etc. • Skin and mucus membranes: Syphilis 4. Mode of transmission (mechanism of transmission of infection): • Refers to the mechanisms by which an infectious agent is transferred from one person to another or from a reservoir to a new host. • Transmission may be direct or indirect. 12/8/2022 23
  24. 24. 5. Portals of entry:- The site in which the infectious agent enters to the susceptible host. Mucus membrane Skin Respiratory tract intravenous lines, urinary catheters, wound sites, open skin lesions, invasive devices. 12/8/2022 24
  25. 25. cont…. • 6. Susceptible host:- Factors that affect the body’s natural ability to fight infection include: 1. presence of underlying disease (diabetes) 2. immun-compromised status (HIV, chemotherapy treatment) 3. nutritional status 4. age (the very young and the very old) 12/8/2022 25
  26. 26. Cont….. 12/8/2022 26
  27. 27. Secondary driving factors 12/8/2022 27
  28. 28. Secondary driving factors. 12/8/2022 28
  29. 29. Carrier and Its Type  carrier is an infected person or animal who does not have apparent clinical disease but is a potential source of infection to others. A. Healthy or asymptomatic carriers: - These are persons whose infection remains unapparent. E.g….. in poliovirus, meningococcus and hepatitis virus infections, there is a high carrier rate. B. Incubatory Carriers : These are individuals or persons who excrete the pathogen during the incubation period. (i.e. before the onset of symptoms or before the characteristic features of the disease are manifested). • E.g. Measles, mumps, chickenpox and hepatitis. 12/8/2022 29
  30. 30. C. Convalescent Carriers: These are those who continue to harbor the infective agent after recovering from the illness. • E.g. Diphtheria, Hepatitis B virus. D. Chronic Carriers: The carrier state persists for a long period of time. E.g. Hepatitis B virus infection 12/8/2022 30
  31. 31. Cont….. Carriers commonly transmit disease ,Because ;-  Asymptomatic;- they do not recognize they are infected and consequently take no special precautions to prevent transmission.  Symptomatic;- persons, on the other hand, are usually less likely to transmit infection widely because:- their symptoms increase their likelihood of being diagnosed and treated, thereby reducing their opportunity for contact with others. 12/8/2022 31
  32. 32. Carrier and time curse of diseases 12/8/2022 32
  33. 33. Levels of Disease Prevention • It is important for implementing interventions that prevent infections. • Involves the interruption or slowing of disease progression through appropriate intervention. • Epidemiology plays a central role in disease prevention by identifying modifiable causes of disease and their risk factors. Three levels, (Primary, Secondary and Tertiary) 1. Primary prevention Primary prevention aims to prevent disease or injury before it ever occurs. The objectives here are to promote health, prevent exposure, and prevent disease.
  34. 34. Primary prevention….cont… • legislation and enforcement • to control the use of hazardous products (e.g. asbestos) or • to mandate safe and healthy practices (e.g. use of seatbelts and bike helmets) • Education about healthy and safe habits (e.g. eating well, exercising regularly, not smoking) • Immunization against infectious diseases. 12/8/2022 34
  35. 35. Cont… A. Health promotion (Primordial): • This consists of general non-specific interventions that enhance health and the body’s ability to resist disease – including: • The improvement of socioeconomic status through the provision of adequately. • paid jobs, • education, • affordable and adequate housing and clothing, etc. B. Prevention of exposure: • There are many examples of interventions aimed at this stage, • Relatively to specific compared to primordial prevention • the provision of safe and adequate water, of proper excreta disposal, • Provision of vector control; • Provision of a safe environment at home
  36. 36. Cont… C. Prevention of disease: An example of intervention, which acts at this stage, is passive immunization. Some times it may be difficult to differentiate interventions in what form of prevention they involved Breastfeeding is an example of an intervention which acts at all three levels of primary prevention.
  37. 37. 2. Secondary prevention • Secondary prevention aims to reduce the impact of a disease or injury that has already occurred. • Strategy is early detecting and treating disease or injury as soon as possible. • The objective is:- • slow its progress, • prevent or limit permanent damage. • encouraging personal strategies to prevent reinjury or recurrence, and • implementing programs to return people to their original health and function to prevent long-term problems. • Examples include: • Regular exams and screening tests to detect disease in its earliest stages (e.g. mammograms to detect breast cancer) • daily, low-dose aspirins and/or diet and exercise programs to prevent further heart attacks or strokes 12/8/2022 37
  38. 38. Cont… 3. Tertiary prevention Intervention that acts after permanent damage has set in, and the objective of tertiary prevention is to limit the impact of that damage. The impact can be physical, psychological, social (social stigma or avoidance by others), and financial. Strategy at this stage in general is rehabilitative.
  39. 39. Principles of communicable diseases control • The common principles and terms used in the prevention and controls of diseases are: Disease control: It refers to the reduction of incidence and prevalence of communicable diseases to a level where it can not be a major public health problem. Disease elimination: It is the reduction of infection and disease to zero in a defined geographical area Disease eradication: It is a permanent reduction of worldwide incidence to zero, as a result of deliberate interventions. Disease extinction: It is a permanent, worldwide eradication the infectious agent including from the laboratory. 12/8/2022 39
  40. 40. ID control…cont..  Control measures are usually directed against the segment in the chain of infection that is most susceptible to intervention. • There are three broad areas /strategies of prevention and control:- 1. Attacking the source (reservoir) of infection. That is to reduce the number of infective organisms. This is done by: a. Treatment of cases and carriers through mass treatment, as in typhoid fever, schistosomiasis, tuberculosis. b. Isolation: separation of infected persons for a period of communicability. N.B. Isolation is indicated when diseases: have high mortality and morbidity. have high infectivity 12/8/2022 40
  41. 41. ID control…cont.. C. Quarantine: limitation of movement of person or animal who has been exposed to infectious disease for a maximum incubation period for the disease. D. Reservoir control: by mass vaccination to cattle and sheep and killing & burning infected animals (rabies, anthrax). E. Active surveillance of contacts F. Effective reporting system 12/8/2022 41
  42. 42. ID control…cont.. 2. Interrupting the chain of transmission It is control of modes of transmission from reservoir to the new host. Environmental sanitation: - e.g for the control of intestinal parasites Personal hygiene: - e.g for trachoma and scabies control.  Vector control :- e.g mosquito control for malaria  Disinfection and sterilization: - e.g purification of potable water, pasteurization of milk. 12/8/2022 42
  43. 43. ID control…cont.. • 3. Reducing host susceptibility: a. Immunization - to create immunity at individual level & herd b. Better and improved nutrition c. Health education d. Chemoprophylaxis:-malaria, meningitis, tuberculosis e. Person protection: - face mask, mosquito nets, clothing, repellents, shoes, etc 12/8/2022 43
  44. 44. Home take assignment 12/8/2022 44
  45. 45. References • 12/8/2022 CDC lecture note set by Minichil G 45
  46. 46. 12/8/2022 46

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