Natural History of Disease and Levels of Prevention PDF

Natural History of Disease and levels of prevention Asst. Prof. Dr. Basheer Al-Ali M.B.Ch.B ABHS/C.M Department of Family and Community Medicine University of Kerbala/ College of Medicine/  Definition Natural history of disease...

Natural History of Disease and levels of prevention Asst. Prof. Dr. Basheer Al-Ali M.B.Ch.B ABHS/C.M Department of Family and Community Medicine University of Kerbala/ College of Medicine/  Definition Natural history of disease: The progress of a disease in an individual over time, in the absence of Medical intervention. The process begins with exposure or accumulation of factors capable of causing disease. Without medical intervention, the process ends with ✓Recovery (Cure) ✓Control ✓Disability ✓Death This is called prognosis of disease  Four stages of the natural history of disease Susceptibility - precedes exposure to the causal agent. Subclinical (preclinical) disease - the stage of disease that follows exposure to the agent but is before symptoms are apparent (incubation period) Clinical disease - the stage of disease associated with signs and symptoms. Recovery, disability, or death - the stage at which disease resolution occurs.  The Natural history of disease in a patient Preclinical Phase Clinical Phase Outcome: Cure Control Disability Death (A) (P) (S) (M) (D) (T) A ; Biologic onset of disease P ; Pathologic evidence of disease if Sought S ; Signs and symptoms of disease M ; Medical care sought D ; Diagnosis T ; Treatment  Latent period the time interval from infection to development of infectiousness Infectious period the time during which the host can infect another susceptible host Non-infectious period the period when the host’s ability to transmit disease to other hosts ceases Incubation period the time interval between infection to development of clinical disease  TIME Death Infection Clinical disease Susceptible host Recovery No infection Incubation period Latent Infectious Non-infectious Exposure  example : Chicken pox An infectious disease caused by the varicella-zoster virus the latent period for chicken pox is shorter than the incubation period, so a child with chicken pox becomes infectious to others before developing symptoms.  TIME Death Infection Clinical disease Susceptible host Recovery No infection Incubation period Latent Infectious Non-infectious Exposure Onset  Other examples: HIV (AIDS) latent period relatively short infectious period occurs (many years) before the onset of symptoms  TIME Death Infection Clinical Susceptible disease host Recovery No infection Incubation period Latent Infectious Exposure Onset Other examples: Malaria the stages of the parasite that are infective occur about 10 days after the development of symptoms latent period is around 10 days longer than the incubation period, so early treatment of symptoms could have an important effect on transmission  Natural history of disease TIME Death Infection Clinical disease Susceptible host Recovery No infection Incubation period Latent Infectious Exposure Onset  Risk factors for disease: BEINGS Model 1. Biological factors and Behavioral factors 2. Environmental factors 3. Immunological factors 4. Nutritional factors 5. Genetics factors 6. Services, Social factors, and spiritual factors Prevention of disease  Prevention of disease Prevention is one of the prime messages of public health. It differentiates public health from the clinical disciplines that are primarily involved with the care of the sick only, whilst public health emphasizes the avoidance of illness. A further extension of prevention to covers the treatment of sick individuals aimed at reversing damage and restoring function.  Definition of Disease Prevention “Prevention is the action aimed at eradicating, eliminating or minimizing the impact of disease and disability.” Classification of prevention  1. Primordial prevention This is a prevention of development of risk factors in a Population group , which they have not yet appeared. Particularly useful for chronic diseases. Example: Many adult health problems (e.g., obesity, hypertension) have their early origins in childhood, because this is the time when lifestyles are formed (smoking, eating patterns, physical exercise). Efforts are directed towards discouraging children from adopting harmful lifestyles. The main intervention – is through individual and mass education.  2. Primary prevention Preventative measures that occur during the stage of susceptibility- intent to reduce new occurrences of disease Measures of prevention undertaken during the phase of pre- pathogenesis (phase of susceptibility) Involves two sub-steps: Health promotion and specific protection  Primary prevention Health Promotion : Steps undertaken to improve the level of general health and well being so that conditions for initiation of disease process are prevented. Examples: improvement in the overall socio-economic status of the population, health education, feeding programmes for mothers and children, promotion of breast feeding, motivation for healthy lifestyle.  Primary prevention Specific Protection : include measures to prevent the initiation of specific diseases or a group of diseases. Examples Immunization to protect against specific diseases Fortification of foods with specific nutrients (as salt with iodine) Use of condoms to protect against sexually transmitted diseases (STDs) Use of helmets to protect against head injuries PRIMARY Target population: entire population with special attention to healthy individuals Objective: prevent onset of illness Methods: education, immunization, nutrition, sanitation, etc.  3. Secondary prevention Preventive measures that occur during the stage of subclinical disease; intended to delay the onset of disease or reduce its duration or severity. classical example is “screening for disease” for breast cancer (using mammography). medical examinations of school children, or industrial workers.  3. Secondary prevention Secondary prevention attempts to arrest the disease process, restore health by seeking out unrecognized disease and treating it before irreversible pathological changes take place, and reverse communicability of infectious diseases. It protects others in the community from acquiring the infection and thus provide at once secondary prevention for the infected ones and primary prevention for their potential contacts. SECONDARY Target population: sick individuals Objective: early diagnosis and treatment to prevent further damage to the individual and in cases of infectious diseases, spread to the community Methods: screening of high risk groups e.g. Sputum examination for TB.  4. Tertiary prevention Preventive measures that occur during the clinical stage of disease- intended to reduce complications and disabilities These include all measures undertaken when the disease has become clinically manifest or advanced, with a view to prevent or delay death, reduce or limit the impairments and disabilities, and minimize suffering. Tertiary prevention has two types of approaches : Disability limitation & Rehabilitation. TERTIARY Target population: sick patients Objective: reduce damage from disease and restore function Method: clinical care and rehabilitation