CONCEPT OF DISEASE
COMMUNITY RESEARCH PROGRAM 1
FAJAR AWALIA YULIANTO
The modern Epidemiology :“Using quantitative methods to study ,
prevent, and control the disease in human population”
CAUSATION OF DISEASE
GENETIC FACTOR
GOOD HEALTH POOR HEALTH
ENVIRONMENTAL FACTORS(INCLUDING BEHAVIOURS)
EVALUATING INTERVENTIONS TREATMENT
MEDICAL CARE
GOOD HEALTH ILL HEALTH
HEALTH PROMOTIONPREFENTIVE MEASURESPUBLIC HEALTH SERVICES
DEFINITION HEALTH
Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
DISEASE Conformed in epidemiology, as simple as
“disease present” and “disease absent”
NATURAL HISTORY OF DISEASE
Good health Sub-clinical changes Clinical changes
Recovery
Death
THE CONCEPT OF CAUSE A cause of a disease or injury is an event,
condition, characteristic or a combination of these factors which plays an important role in producing the health outcome
IS THE CAUSE SUFFICIENT OR NECESSARY FORMING THE DISEASE?
Sufficient if: It inevitably produces or initiates an outcome
Necessary if: An outcome can not develop in its absence
EACH SUFFICIENT CAUSE HAS A NECESSARY CAUSE AS A COMPONENT
FACTORS IN CAUSATION Predisposing factors : age, sex, genetic traits
and previous illness may create susceptibility Enabling (Disabling) factors : low income, poor
nutrition, bad housing and inadequate medical care may favor the development of illness
Precipitating factors : exposure to a specific disease agent or noxious agent may be associated with the onset of disease
Reinforcing factors : repeated exposure, unduly hard work may aggravate an established disease or injury
TRADITIONAL MODEL OF INFECTIOUS DISEASE CAUSATION
AGENT as an element or substance, animate or in
animate,the presence (or absence) of it may initiate or perpetuate a disease process.
COMPONENTS OF AGENT Nutritional Chemical Physical Infectious
HOST A person or other living animal, that
affords subsistence or lodgment to an infectious agent under natural condition.
COMPONENTS OF HOST The age Sex Genetic-Hereditary Ethnic / race Physiologic / Psychological status Habit / tingkah laku Immunologic status The previous illnes
ENVIRONMENT As the aggregate of all the external
conditions and influence affecting the life and development of an organisme.
COMPONENTS OF ENVIRONMENT Physical environment : such as
Geographic, Geology, Climate Biological environment : such as people,
flora, fauna ; population density, food Socioeconomic, such as : income,
education, culture, urbanization, economic growth, poverty, fertility etc.
CONSIDERATIONS FOR CAUSATION Temporal relation:
Does the cause precede the effect? (essential) Plausibility
Is the association consistent with the other knowledge? (MOA, evidence from experimental animal)
Consistency Have similar results been show in other study?
Strength What is the strength of the association between the cause and the effect? (relative
risk) Dose-response relationship
Is increased exposure to the possible cause associated with increased effect? Reversibility
Does the removal of a possible cause lead to reduction of disease risk? Study design
Is the evidence based in a strong study design? Judging the evidence
How many lines of evidence lead to the conclusion?
TERMS IN DISEASE
THE INCUBATION PERIOD The time interval between contact with an agent
and the first clinical evidence of resulting disease .
It depends on : Portal of entry ( there is a defense mechanism) The ability of multiplication (infectivity). Number of agents Level of antibody in the host
It varies individually
Type of incubation period in the disease outbreak
A : skewed to the left, when the disease has a short incubation periodB : skewed to the right, when the disease has a longer incubation period
A B
DEFENSE MECHANISM THE ABILITY TO REACT AGAINST AGENT
INVASION IN THE BODY :
Consist of : The external defense mechanism such as
physical and chemical reaction. The internal defense mechanism : cellular
and humoral immunity
INTERLUDE
The lightwave travel not in straight singular waveform. The further, the more curvature it formed.
TYPES OF DISEASES Communicable diseases Chronic non communicable diseases
COMMUNICABLE DISEASES
The leading communicable diseases in the world are:
1. Acute respiratory infections (3,76 millions)2. HIV/AIDS (2,8 millions)3. Diarrhoeal diseases (1,7 millions)4. Tuberculosis (1,6 millions)5. Malaria (1 million)6. Measles (0,8 million)
COMMUNICABLE DISEASES
1.Directly, from other infected humans or animals
2.Indirectly, through vectors, airborne particles or vehicles
COMMUNICABLE DISEASES Vectors: insects or animals that carry
infectious agents from person to person Vehicles: contaminated objects or elements
of the environment Contagious: ability to spread between
humans without intervening vector or vehicle
COMMUNICABLE DISEASES Epidemics: the occurence of cases in excess
of what is normally expected in a community or region
Endemic: the relatively stable pattern of occurence in a given geographical area or population group at relatively high prevalence and incidence
COMMUNICABLE DISEASESCHAIN OF INFECTION The Infectious agent The transmission process The host The environment
COMMUNICABLE DISEASESTHE INFECTIOUS AGENT
The factors determining the nature of the infection:1. Pathogenicity: The ability to produce a disease.
Measured by ratio number of persons whom clinically ill compared to the exposed
2. Virulence: The severity of disease3. Infective dose: The amount required to cause
infection in susceptible subjects4. Reservoir: The natural habitat5. Source of infection:The person or object from wich
the host acqures the agent
COMMUNICABLE DISEASESTHE TRANSMISSION PROCESS
1. Direct transmission2. Indirect transmission
COMMUNICABLE DISEASESTHE HOST Extremely vary between individuals Determined by self-reaction to the agents
COMMUNICABLE DISEASESENVIRONMENT Plays a critical role in the development of
communicable diseases
CHRONIC NON COMMUNICABLE DISEASES
The leading chronic diseases in the world are:1. CVD (17,5 million deaths)2. Cancer (7,5 million deaths)3. Chronic respiratory disease (4 million
deaths)4. Diabetes (1,1 million deaths)
CHRONIC NON COMMUNICABLE DISEASES
The underlying determinants of health and their impact on chronic diseases
Socioeconomics,Cultural, political &
Environmental factors
Common Modifiable & nonmodifiable risk
factors
IntermediateRisk factors
Main chronicdiseases
CHRONIC NON COMMUNICABLE DISEASES
Levels of prevention:1. Primordial prevention2. Primary prevention3. Secondary prevention4. Tertiary prevention
Level Phase of disease
Aim Actions Target
Primordial Underlying economic, social, environmental conditions leading to causation
Establish and maintain conditions that minimize hazards to health
Measures that inhibit the emergence of environmental, economic, social and behavioral conditions
Total population or selected groups; achived through public health policy and health promotion
Primary Specific causal factors
Reduce the incidence of disease
Protection of health by personal and communal efforts, such as enhancing nutritional status, providing immunization, and eliminating environmental risks
Total population, selected groups and healthy individuals; achieved through public health policy
Secondary Early stage of disease
Reduce the prevalence of disease by shortening its duration
Measures available to individals and communities for early detection nd prompt intervention to control disease and minimize disability (e.g. Through screening programs)
Individuals at igh risk and patients; achieved through preventive medicine
Tertiary Late stage of disease (treatment, rehab)
Reduce the number and/or impact of complications
Measures aimed at softening the impact of long-term disease and disability; minimizing suffering; maximizing potential years of useful life
Patients; achieved through rehabilitation
REFERENSI Bonita, R., Beaglehole, R., Kjellstrom, T.
Basic epidemiology, 2nd ed. Geneva, World Health Organization, 2006