Natural History of Diseases PDF

Natural History of Diseases BSc Medical Sciences: Epidemiology Assistant Prof. Dr. Soza Th. Baban Introduction and Review In session 6, we discussed: Disease surveillance is essential for detecting, responding to, and preventing outbreaks. Effective disease surveillance systems require accu...

Natural History of Diseases BSc Medical Sciences: Epidemiology Assistant Prof. Dr. Soza Th. Baban Introduction and Review In session 6, we discussed: Disease surveillance is essential for detecting, responding to, and preventing outbreaks. Effective disease surveillance systems require accurate data, timely reporting, and international cooperation. - Different types of surveillance systems serve different needs, from local to global. Challenges, eimportance and the role of disease surveillance in preventing and controlling outbreaks. - Learning objectives How the disease Start and progress > - Explain the natural history of disease and the stages of - disease progression and provided with case scenarios. infectious disease Differentiate between communicable and non- non-infectious - communicable - diseases in the context of natural history. Discuss how social, economic, and cultural factors affect disease progression. Let’s go through each of these points in detail!  When your body doesn't I ease CONCEPT OF DISEASE - - work as it should , not being "a condition in which body health is impaired, a departure from a state of health, an alteration of the human body interrupting the performance of - vital functions". 1 Disease is just the opposite of health - i.e., any deviation from normal functioning or state of complete physical or mental well-being. The term "disease" literally means "without ease" (uneasiness) - disease, the opposite of ease - when something is wrong with bodily function. " Shows full cycle this is about how the disease of the disease 2 Natural History of Disease progresses naturally without any From start to Finish , treatment or prevention It signifies the way in which a disease evolves over time from the (Beforethe disease starts) earliest stage of its prepathogenesis phase to its termination as recovery, disability or death, in the absence of treatment or prevention. ❑ For an infectious disease, the exposure is a causative agent. ❑ For cancer, the exposure may be a factor that initiates the process, such as asbestos fibers ( toxic, carcinogenic and fibrous silicate minerals ) or components in tobacco smoke (for lung cancer), or one that promotes the process, such as estrogen (for endometrial cancer).  Natural History of Disease is a time live - It signifies the way in which a disease evolves over time from the earliest stage- of its prepathogenesis phase to its J termination as recovery, disability or death, in the absence of treatment or prevention. The risk exists shows but the disease hasn't started. 1) How the disease starts 2) How it grows and spreads 3) How it ends·  Natural History of Disease Definition The natural history of disease is the uninterrupted progression of disease from its initiation to either spontaneous resolution, containment by the body’s repair mechanisms, or to a clinically detectable problem.  Natural History of Disease It signifies the way in which a disease evolves over time from the earliest stage of its prepathogenesis phase to its termination (outcome) as recovery, disability or death, in the - absence of treatment or prevention. think about we mortality and morbidity Outcome (Final stage) 1) Recovery - person gets better stage when the disease become 2) Disability > cause - Logeuge this stage Visible disease has started happens before the in the body but Symptoms appear 3) Death > - Fatal feel disease the person doesn't begins Sick yet ! (Silent phase) (INCUBATION  Natural History of Disease imp depend on this diagram others are for illustration Susceptibility Stage: Before the onset of the disease. Before you get infected Subclinical Disease Stage: Pathological changes occur, but no symptoms are present (e.g., incubation period for infectious diseases, latency period for chronic diseases). - you're infected but , no symptoms appear - - Clinical Disease Stage: Symptoms becomes visible, and the disease is - diagnosed. Either - to reduce this we create programs as epidemiologist Recovery, Disability, or Death: The final outcomes of the disease. - Natural History of Disease Infectious disease as a model  ⑪ Only know the stages The natural history of disease in a patient ⑯ The progression of the disease process (A): Biologic onset of disease. Often, this point cannot be identified because it occurs subclinically, perhaps as a subcellular change, such as an alteration in DNA. (P): Pathologic evidence of disease could be obtained if it were sought by population screening or by a physician. (S): signs and symptoms of the disease develop in the patient. (M): the patient may seek medical care. (D): The patient may then receive a diagnosis; (T): Treatment may be given; (OUTCOME): The subsequent course of the disease might result in cure or remission, control of the disease (with or without disability), or even death.  Natural History of Disease 1. Prepathogenic phase is the period before the disease starts. This refers to the period preliminary to the onset of disease in human. The disease agent has -not yet entered human body, but the factors which favour its interaction with the human host are already existing in the environment. *the person doesn'thavethe disease yet but conditions that could cause the disease are , already present This situation is frequently referred to as “human in the midst of disease" or - “human exposed to the risk of disease". - Potentially we are all in the prepathogenesis phase of many diseases, both communicable and non-communicable.  Natural History of Disease 1. Prepathogenic phase The causative factors of disease may be ① - ⑧ classified as AGENT, HOST and & the thing the person ENVIRONMENT. that mightcause who The surrovedings that make disease get the the disease more to happen disease likely An interaction of these three factors is required to initiate the disease process in human; - determine the onset of disease which may range from a single case to epidemics; - the distribution of disease in the community.  Natural History of Disease 1. Prepathogenic phase Screening is the application of tests to diagnose disease (or precursors) in an earlier phase of the natural history of disease, often in well people, or in a less severe part of the disease spectrum than is achieved in routine medical practice. Natural History of Disease 1. Pathogenesis phase In infectious diseases; The pathogenesis phase begins with the entry of the disease "agent" in the susceptible human host. Disease agents include: Biological agents → microbes Nutrient agents→deficiency in vitamins Physical agents → radiation Chemical agents → jaundice (serum bilirubin), heavy metals, insecticides Mechanical agents → chronic frinction Social agents → smoking Natural History of Disease 1. Pathogenesis phase The disease agent multiplies and induces tissue and physiological changes, the disease progresses through a period of incubation and later through early and late pathogenesis.  Natural History of Disease 2. Pathogenesis phase It is useful to remember at this stage that the host's reaction to infection with a not necessary disease agent is not predictable. for to - symptoms appear The infection may be clinical (clear lincubation period) symptoms) or subclinical (no symptoms at all);& Ctypical ommon (e.g., fever and rash are typical symptoms of measles) or A can not atypical diagnosethe disease accordingto symptoms (unusual symptoms) or the host may - become a carrier with or without having developed clinical disease as in the case of diphtheria and hepatitis B. Natural History of Disease 2. Pathogenesis phase In chronic diseases (e.g., coronary heart disease, hypertension, cancer), this phase is referred to as = presymptomatic phase. During the presymptomatic stage, the pathological changes are essentially below e - - the level of the "clinical horizon". - & Signs symptoms still doesn't appear The clinical stage begins when recognizable signs or symptoms appear. By the time signs and symptoms appear, the disease phase is already well advanced into the late pathogenesis phase.  (Session7 – Scenario descriptions) Scenario 1: Outbreak of Measles in a Low-Income Urban Community Scenario 2: Rising Diabetes Rates in a Rural Community Scenario 3: Tuberculosis in an Overcrowded Refugee Camp (1) asseg Scenario 1: Outbreak of Measles in a Low-Income Urban Community - ↑ A low-income urban area has reported a sudden increase in measles cases, primarily among children under five. The community has limited healthcare facilities, low vaccination rates, and poor access to clean water and sanitation. Many residents lack awareness about vaccination benefits due to limited health education resources. Data for Analysis: Stages of Disease Progression: i. Susceptibility: Children in the area lack immunity due to low vaccination rates. ii. Subclinical: Infected individuals may be asymptomatic initially but are contagious. iii. Clinical Disease: Symptoms include high fever, cough, and a red rash spreading from on the face downward.-Early Stagetsevere symptoms iv. Outcome: Potential for complications such as pneumonia, which can be fatal. - Epidemiological Triad: i. Agent: Measles virus. ii. Host: Susceptible children, especially under five years. iii. Environment: Crowded living conditions, poor sanitation, and low vaccination coverage. Socio-Economic and Cultural Factors: i. Economic: Limited healthcare resources and low income restrict healthcare access. ii. Social: High-density living increases the spread, while lack of education on vaccination fuels hesitancy. iii. Cultural: Some community beliefs discourage vaccination, preferring traditional remedies. Objective: Outline an intervention plan, identifying public health measures (e.g., vaccination drives, educational campaigns) that consider these factors. B Scenario 2: Rising Diabetes Rates in a Rural Community A rural community has shown a steady increase in type 2 diabetes cases. The population primarily relies on a carbohydrate-heavy diet due to economic constraints, with limited access to fresh produce. Physical activity levels are low due to lifestyle and work demands, and there is little knowledge about diabetes prevention. Data for Analysis: Stages of Disease Progression: o Susceptibility: High-risk population due to dietary habits, family history, and lifestyle. o Subclinical: Elevated blood glucose levels may go undiagnosed for years. o Clinical Disease: Diagnosed cases begin to experience symptoms, including fatigue, excessive thirst, and blurred vision. o Outcome: Risk of complications like heart disease, kidney damage, and nerve damage. Epidemiological Triad: o Agent: Lifestyle-related risk factors (diet, physical inactivity). o Host: Genetic predisposition, older adults. o Environment: Lack of healthy food options, cultural acceptance of high-carbohydrate diets. Socio-Economic and Cultural Factors: o Economic: Limited access to diverse food options and healthcare facilities. o Social: Physical activity is not prioritised or accessible in the community. o Cultural: Dietary preferences favour high-carb foods, and there is little awareness about chronic disease prevention. Objective: Students should devise a community intervention plan to promote lifestyle changes, increase awareness, and integrate diabetes screening and management support. Scenario 3: Tuberculosis in an Overcrowded Refugee Camp  Description: An overcrowded refugee camp has reported rising cases of tuberculosis (TB). The residents face malnutrition, inadequate healthcare, and a lack of personal protective measures. Many have fled regions where TB is common, increasing the likelihood of latent cases becoming active due to stressful conditions. prevention ① avoid over crowding vaccination are ② provide Data for Analysis: Stages of Disease Progression: Natural disease stage (disease progression) i. Susceptibility: High due to -malnutrition and close contact with infected individuals. ii. Subclinical: Latent TB infections with no symptoms but potential for spread if immunity is compromised. PCR tests can diagnosethis disease Patient e shou d iii. Clinical e fever. O Disease: Active TB symptoms include persistent cough, weight loss, and with blood ⑮ iv. Outcome: Risk of death if untreated, with potential for ongoing transmission. Epidemiological Triad: i. Agent: Mycobacterium tuberculosis (TB bacteria). Malnourished stressed> - individual ii. Host: Immunocompromised individuals, often due to malnutrition or stress. iii. Environment: Overcrowded, poorly ventilated living conditions, lack of medical care. Socio-Economic and Cultural Factors: i. Economic: Limited resources in the camp restrict healthcare and sanitation. -limiting ii. Social: Overcrowding and poor ventilation facilitate TB transmission. Riding a going iii. Cultural: Language barriers and mistrust of foreign healthcare providers can hinder TB treatment and prevention efforts. Objective: Students should develop an intervention plan that includes screening, treatment, and preventive education, while addressing cultural and logistical barriers. (2) Applying the Natural History of Disease to Public Health Planning This worksheet aims to guide students in applying the concept of the natural history of disease to public health planning. - Students will design an intervention plan for a chosen disease, considering its progression, the Epidemiological Triad, and relevant social, economic, and cultural factors. Scenario Selection Choose one of the following scenarios for your public health intervention planning. You will analyse the disease progression and develop an intervention strategy based on the principles learned: 1. Chronic Disease: Develop a public health intervention to reduce the incidence and manage the progression of Type 2 Diabetes in an urban population with limited healthcare access. 2. Communicable Disease: Design an intervention to control the spread and manage an outbreak of measles in a low-income community with low vaccination rates. Part 1: Disease Progression and Stages In this section, you will map out the stages of disease progression for your chosen disease based on its natural history. Use the provided readings and class discussions to - structure your responses. -  1. Susceptibility Stage i. Define the susceptibility stage for your selected disease. ii. Identify key risk factors that make individuals or populations more susceptible to this disease. iii. What preventive measures could be applied during this stage to reduce susceptibility? Response: susceptibility - > the stage where people are at risk but don't have the disease yet- Risk factors Pour health habits > - lack of vaccination limited access to , , heat prevention Educate people about &> healthy lifestyle or importanceofvace 2. Subclinical Disease Stage i. Describe the subclinical stage for your chosen disease (e.g., incubation period for communicable diseases, latency period for chronic diseases). ii. What early detection measures could be applied during this stage? iii. How would you design an intervention that targets this stage to prevent disease progression? Response: subclinical diseases The stage where the disease - is but has present no symptoms- Detection & > - Early testing screening - promote regular checkups > - Intervention for prevention > - ② start early treatment ③ preventative care to stop the disease from appearing  3. Clinical Disease Stage Describe the clinical stage, where symptoms manifest, and diagnosis is typically made. What treatment or intervention strategies can be employed to manage the disease at this stage? What resources are required to implement these interventions effectively (e.g., healthcare access, medication)? Response: Clinical stage the stage where symptoms and the disease diagnose > appear , - > - is > - treatment - > Use medication vaccines or other medical care to treat disease , ,. > - Provide education & support for managing illness. Resources needed & trained health are worker ③ proper facilities affordable medication , 4. Recovery, Disability, or Death What are the potential outcomes of the disease (e.g., recovery, chronic disability, death)? How can public health interventions support recovery and reduce disability or mortality rates? What role does rehabilitation or long-term care - > for those with complication play in this stage? Response: Outcome > Recovery with proper cre provide longterm Intervention - long term complication > - care follow ups to improve quality of Death in severe cases life Part 2: Applying the Epidemiological Triad Using the Epidemiological Triad (Agent, Host, Environment), explain the factors that contribute to the disease causation and progression in your selected scenario. Be specific and draw from examples discussed in class or in the readings. 1. Agent o Identify the agent responsible for the disease (e.g., bacteria, virus, genetic factors, lifestyle factors). o What characteristics of the agent influence the spread or progression of the disease? Response: Agent- > the cause of the re disease lifestyle > it tells you - how it speeds or progressed - E/Infectious agents , Bad herbits) 2. Host Identify the host factors (e.g., genetic predisposition, immune response, behaviour) that contribute to susceptibility and progression. How do individual or population-level factors affect the host’s ability to resist or recover from  the disease? Response: Host - > The one that is affected (People who are at risk) due to Geneticsa ↳ Heathstatus Factors like poor t => immunity & Obesit Lack of awareness 3. Environment o Describe environmental factors that contribute to the onset and spread of the disease (e.g., living conditions, healthcare infrastructure, sanitation). o How can changes in the environment reduce the impact of the disease? Response: Environment > (means-> what contributes to get the disease) changes in environment can improve access to health clean living care , condition and safe spaces. Part 3: Social, Economic, and Cultural Factors Discuss the social, economic, and cultural factors that should be considered when designing your intervention. Use examples and research to support your answers. 1. Social Factors How do access to healthcare, education, and social support systems influence disease progression and public health outcomes in your scenario? What social strategies could be employed to reduce health disparities related to the disease? Response: Social Factors ① Health Improve availability and care access > - affordable care , ② Education > - Increase heath care awareness ③ Supportsystemsig Build local supportnetwork and pation 2. Economic Factors How does income level, employment status, and economic policies affect disease management and access to interventions? What cost-effective solutions could be incorporated into your intervention plan? Response: S ①  3. Cultural Factors How do cultural beliefs, practices, and behaviours influence the spread or management of the disease? How can your intervention be adapted to respect cultural norms while effectively managing the disease? Response: Part 4: Public Health Intervention Plan Based on your analysis, develop a comprehensive public health intervention plan. Your plan should address the following elements: 1. Goals and Objectives o What are the primary goals of your intervention? o Define measurable objectives to track the success of your intervention (e.g., reduce incidence by 10% in two years, increase vaccination rates). Response:  2. Target Population o Who is your target population? Consider factors such as age, gender, socio-economic status, and location. o How will you reach this population effectively? Response: 3. Intervention Strategies o What specific intervention strategies will you employ? These may include vaccination campaigns, health education, early screening programs, policy changes, etc. o For each strategy, describe how it addresses the stages of disease progression and factors discussed in Parts 2 and 3. Response:  4. Resources Needed o What resources (financial, human, technological) will be needed to implement your intervention? o How will these resources be allocated and managed? Response: 5. Monitoring and Evaluation o How will you monitor the progress of your intervention? o What evaluation methods will you use to measure success and make necessary adjustments? Response: Part 5: Group Discussion and Presentation After completing your worksheet, present your intervention plan to the class. Engage in a reflective discussion on the following: 1. What are the strengths and potential challenges of your intervention plan? 2. How does understanding the natural history of disease contribute to effective public health planning? 3. How can the social, economic, and cultural factors inform public health policies you discussed?  Communicable vs. Non-Communicable Diseases Communicable Diseases: Spread from one person to another (e.g., Flu, COVID-19). Usually have a clear incubation period and rapid progression. Non-Communicable Diseases: Chronic diseases not passed from person to person (e.g., Diabetes, Cancer). Often long-term, with a slower progression, influenced by lifestyle and environment.  Impact of Social, Economic, and Cultural Factors Factors that influence disease progression include: Social: Access to healthcare, education, and social networks. Economic: Income, employment, and the ability to afford treatment. Cultural: Beliefs, practices, and attitudes towards health and treatment.  Applying the Natural History of Disease in Public Health Public health strategies use the knowledge of disease progression to: Design effective interventions targeting early stages. Implement vaccination, screening, or early treatment programs. Monitor and assess outcomes based on disease patterns.  (Session7 – The worksheet) Applying the Natural History of Disease to Public Health Planning 1. Chronic Disease: Type 2 Diabetes 2. Communicable Disease: an outbreak of measles  Recap and Q&A Key Points from Today’s Lecture: Identified the stages of disease progression and discussed with different case scenarios. The social, economic, and cultural factors on disease progression discussed with the activity of applying the natural history of disease to public health planning and designing the intervention plan for chosen disease. Preparation for Next Session In the next session we'll explore the Descriptive studies in epidemiology. i. Read Chapter 4 (Pages 70-78) from "Parks Textbook of Preventive & Social Medicine" by K. Park. ii. Review Chapter 7 (Pages 149-177) from "Gordis Epidemiology" by Celentano DD and Szklo M. iii. Research examples of descriptive epidemiological studies and their contributions to public health. iv. Prepare to discuss the types and uses of descriptive studies in the next session.