Cl 02 principles in control and prevention of communicable diseases
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The document discusses principles of disease prevention and control, describing the epidemiologic triangle of agent, host, and environment factors in disease transmission. It explains the stages of disease from susceptibility to recovery and the types of prevention for each stage - primary prevention aims to reduce new occurrences, secondary prevention reduces duration and severity, and tertiary prevention minimizes complications. Examples are given for prevention and control strategies across communicable and non-communicable diseases.
Cl 02 principles in control and prevention of communicable diseases
- 1. Dr Norfazilah Ahmad Department of Community Health UKM Medical Centre 5th September 2012
- 2. Relationship between agent, host and environment and human in diseases transmission Discuss the principles of disease prevention Describe methods of control and prevention used for communicable diseases Definition: diseases prevention, control, elimination, eradication , extinction, isolation and quarantine Examples
- 4. Traditional model of infectious disease causation. Three components: an external agent, a susceptible host, and an environment that brings the host and agent together.
- 5. Epidemiologic triangle and triad (balance beam) HOST AGENT HOST ENVIRONMENT AGENT ENVIRONMENT
- 6. AGENT FACTORS ◦ Biological – bacteria, virus, parasites, fungi ◦ Physical – physical forces, heat, radiation, noise ◦ Chemical – contaminants, poisons, drugs, allergens ◦ In general, agents must be present for disease to occur .
- 7. HOST FACTORS ◦ Intrinsic factors that influence an individual’s exposure, susceptibility, or response to a causative agent. ◦ Example: age, race, sex, socioeconomic status, behaviors, nutritional status etc.
- 8. ENVIRONMENTAL FACTORS ◦ Extrinsic factors which affect the agent and the opportunity for exposure. ◦ Example; physical factors such as geology, climate and physical surroundings; biologic factors such as insects that transmit the agent; and socioeconomic factors such as crowding, sanitation, and the availability of health services.
- 9. HOST AGENT Increasing ability in agent to cause infection in host ENVIRONMENT AGENT Increase susceptible host HOST in the community ENVIRONMENT
- 10. HOST Changes in environment that cause agent transmission AGENT ENVIRONMENT AGENT Changes in the environment that increase the host susceptibility to the disease ENVIRONMENT HOST
- 13. Using Avian flu as an example of the chain of infection; The pathogen is the H5N1 virus. The reservoir is wild migratory waterfowl. The pathogen exits the wild fowl through the faeces. It is transmitted through direct contact with infected materials. It enters the susceptible host, in this case, humans, through direct contact with mucous membranes or through small droplet nuclei.
- 15. Onset of Exposure Symptoms Incubation period Pathologic changes Time of diagnosis Stage of Stage of Stage of Stage of susceptibility Subclinical Disease Clinical Disease Recovery, Disability, or Death Stages in the natural history of disease
- 16. Corresponds to time during which the etiologic agent is present within the body but has not yet caused signs or symptoms Both infectious and noninfectious diseases are characterized by subclinical stages of disease. In infectious diseases – incubation period In noninfectious diseases – latent period or induction period
- 17. Incubation periods vary considerably according to agent-disease pairs Some diseases have ◦ short incubation periods e.g. cholera 24-48 hour, ◦ intermediate e.g. chickenpox 2-3 weeks ◦ extended e.g. AIDS 10 years Latency Period for NCD : ◦ Leukemia due Hiroshima atomic bomb 2-12 years ◦ Occupational associated bladder tumors in GB 5-40 years Variability in incubation and latency can be due to differences in host susceptibility, pathogenicity of the agent, and dose exposure.
- 18. Begins with patient’s first symptoms and ends with either recovery, disability and death Depending on host factors, access to health care, and the diagnostic certainty of the clinician in charge, the lag between the onset of symptoms and diagnosis may vary considerably. The onset of symptoms - not the time of diagnosis – marks the beginning of the clinical stage of disease
- 19. Infectivity refers to the proportion of exposed persons who become infected. Pathogenicity refers to the proportion of infected persons who develop clinical disease. Virulence refers to the proportion of persons with clinical disease who become severely ill or die.
- 21. Disease prevention covers measures not only to prevent the occurrence of disease, such as risk factor reduction, but also to arrest its progress and reduce its consequences once established
- 22. Disease prevention efforts can be classified according to the stage of disease they are applied: ◦ Primary prevention ◦ Secondary prevention ◦ Tertiary Prevention
- 23. Directed toward the stage of susceptibility, before the pathogen establishes itself in the body Goals : ◦ to prevent disease from occurring ◦ reducing its incidence and prevalence in the community ◦ Example: needle exchange programs to prevent the spread of HIV, vaccination programs, smoking cessation campaign
- 24. Stages in the natural Onset of history of Exposure Symptoms disease and type of prevention Incubation period Pathologic changes Time of diagnosis Stage of Stage of Stage of Stage of susceptibility Subclinical Disease Clinical Disease Recovery, Disability, or Death Secondary Prevention: Tertiary Primary Intended to Prevention: Prevention: Level of reduce Intended to Intended to reduce new duration and reduce Prevention severity complications occurrences and disabilities
- 25. Directed toward the subclinical stage, people who carry the agent in their bodies but are not yet symptomatic Goal: ◦ To reduce the expression or severity of the disease once it emerges. ◦ Example; treating asymptomatic HIV infected pts with combination of antiviral agents, screening for cervical cancer and breast cancer to detect the diseases in their early stages.
- 26. Stages in the natural Onset of history of Exposure Symptoms disease and type of prevention Incubation period Pathologic changes Time of diagnosis Stage of Stage of Stage of Stage of susceptibility Subclinical Disease Clinical Disease Recovery, Disability, or Death Secondary Prevention: Tertiary Primary Intended to Prevention: Prevention: Level of reduce Intended to Intended to reduce new duration and reduce Prevention severity complications occurrences and disabilities
- 27. Directed toward the clinical stage Goal : ◦ To prevent or minimize the progression of the disease or its sequelae ◦ Example; screening people with diabetes for diabetic retinopathy in order to promptly treat the progression of blindness
- 28. Stages in the natural Onset of history of Exposure Symptoms disease and type of prevention Incubation period Pathologic changes Time of diagnosis Stage of Stage of Stage of Stage of susceptibility Subclinical Disease Clinical Disease Recovery, Disability, or Death Secondary Prevention: Tertiary Primary Intended to Prevention: Prevention: Level of reduce Intended to Intended to reduce new duration and reduce Prevention severity complications occurrences and disabilities
- 30. Control: ◦ The reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts; ◦ Continuous intervention measures are required to maintain the reduction. ◦ Example: diarrhoeal diseases.
- 31. Isolation ◦ In epidemiology isolation refers to a procedure used in communicable disease control. It consists of a separation of cases (persons or animals) for a disease's period of communicability. ◦ The cases are isolated in a specific location and under conditions that minimize the risk of direct or indirect transmission of the infectious agents to those who may be susceptible
- 32. Quarantine ◦ Quarantine is defined as a restriction of the activities of healthy persons or animals who have been exposed to a communicable disease. ◦ The aim is to prevent transmission of the disease from potentially infected persons to healthy persons during the incubation period. ◦ Quarantine can take two forms: absolute or complete quarantine, which consists of a limitation of freedom for a period equal to the longest usual incubation period of the disease; modified quarantine, which involves selective or partial limitation of movement, based on known differences in susceptibility.
- 33. Elimination of disease: ◦ Reduction to zero of the incidence of a specified disease in a defined geographical area as a result of deliberate efforts; continued intervention measures are required. Example: neonatal tetanus. Elimination of infections: ◦ Reduction to zero of the incidence of infection caused by a specific agent in a defined geographical area as a result of deliberate efforts; continued measures to prevent re- establishment of transmission are required. Example: measles, poliomyelitis. Eradication: ◦ Permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer needed. Example: smallpox.
- 34. Extinction: ◦ The specific infectious agent no longer exists in nature or in the laboratory.
- 35. Endemic - means a disease occurs continuously and with predictable regularity in a specific area or population . Epidemic - a widespread outbreak of an infectious disease where many people are infected at the same time. Outbreak - an epidemic limited to localized increase in the incidence of a disease, e.g., in a village, town, or closed institution Pandemic - an epidemic occurring worldwide, or over a very wide area, crossing international boundaries, and usually affecting a large number of people.
- 36. Cholera (V. cholerae) Primary prevention ◦ Health education ◦ Management of water supply, sanitation and food hygiene ◦ Vaccine? Secondary prevention ◦ Early detection and treatment (ORS and antibiotic) Tertiary prevention ◦ Rehabilitation
- 37. Dengue fever Primary prevention ◦ Health education ◦ Environment sanitation, human behaviour ◦ Mosquitoe net, bed nets,Vaccine? Secondary prevention ◦ Early detection and treatment ◦ Isolation or quarantine? Tertiary prevention ◦ Prevent/reduce complication ◦ rehabilitation
- 38. •Host immunity •Vaccine? Dengue Prevention using the •Protective Behaviour agent, host, environment model Host Agent Environment •Dengue serotype •Aedes breeding •Sanitation •Community behaviour •Climate
- 39. Prevention and Control Of Communicable Disease