concept of disease

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