الرحيم الرحمن الله الرحيم بسم الرحمن الله بسم

CHAIN OF INFFECTONCHAIN OF INFFECTON

THE CHAIN OF INFFECTIONTHE CHAIN OF INFFECTION

Agent factorsAgent factors It is a substance, living or non-living, or It is a substance, living or non-living, or

a force tangible or intangible, the a force tangible or intangible, the excessive presence or relative lack of excessive presence or relative lack of which may initiate or perpetuate a which may initiate or perpetuate a disease process.disease process.

A disease may have a single agent, a A disease may have a single agent, a number of independent alternative number of independent alternative agents or a complex of two or more agents or a complex of two or more factors whose combined presence is factors whose combined presence is essential for the development of the essential for the development of the disease.disease.

Types of Causative AgentsTypes of Causative Agents

Biological agentsBiological agents Nutrient agentsNutrient agents Physical agentsPhysical agents Chemical agentsChemical agents Mechanical agentsMechanical agents Absence or insufficiency or excess of a Absence or insufficiency or excess of a

factor necessary to healthfactor necessary to health Social agentsSocial agents

Host factorsHost factors Demographic :Demographic : age, sex, age, sex, ethnicityethnicity Biological:Biological: genetic factors, genetic factors,

Biochemicals levels of blood, hormones, Biochemicals levels of blood, hormones, functions of organs.functions of organs.

Social and economic:Social and economic: socio-economic socio-economic status, education, occupation, stress, status, education, occupation, stress, marital status, housing, etc.marital status, housing, etc.

Lifestyle factors:Lifestyle factors: personality traits, personality traits, living habits, nutrition, physical exercise, living habits, nutrition, physical exercise, use of alcohol, drugs and smoking etc.use of alcohol, drugs and smoking etc.

Environmental factorsEnvironmental factors

All that which is external to the All that which is external to the individual human host, living and individual human host, living and

non living and which he is in non living and which he is in constant interaction.constant interaction.

Physical EnvironmentPhysical Environment Biological EnvironmentBiological Environment Psychosocial Environment.Psychosocial Environment.

Psychosocial EnvironmentPsychosocial Environment

Those factors affecting personal health, health Those factors affecting personal health, health care and community wellbeing that stem from care and community wellbeing that stem from the psychosocial make up of individuals and the psychosocial make up of individuals and structure and functions of social groups.structure and functions of social groups.

Cultural values, customs, habits, beliefsCultural values, customs, habits, beliefs Attitude, morals, religion, educationAttitude, morals, religion, education Life style, Community Life, Health servicesLife style, Community Life, Health services Social & political Organization.Social & political Organization.

POSITIVE IMPACT IMPACT Improve HealthProvide opportunitiesImprove quality of Life

NEGATIVE IMPACT:Poverty, Urbanization, Migration, Stressful

Conditions, bereavement, desertion, loss of employment, handicapped child, anxiety, depression, Anger, frustration.

Risk factorsRisk factors An attribute or exposure that is significantly An attribute or exposure that is significantly

associated with the development of a diseaseassociated with the development of a disease A determinant that can be modified by A determinant that can be modified by

intervention, thereby reducing the possibility of intervention, thereby reducing the possibility of occurrence of a disease or other specified occurrence of a disease or other specified outcome.outcome.

Non –Modifiable ( Non –Modifiable ( immutable)immutable)

Age, Sex, Genetic Factors & ethnicity. Age, Sex, Genetic Factors & ethnicity. Modifiable Factors ( Modifiable Factors ( mutable)mutable)

Smoking, hypertension, elevated serum Smoking, hypertension, elevated serum cholesterol, physical inactivity, obesity, etc..cholesterol, physical inactivity, obesity, etc..

Risk ApproachRisk Approach

Something for all, but more for Something for all, but more for those in need - in proportion to those in need - in proportion to the need" Therefore it is stated the need" Therefore it is stated

that risk factor is a proxy for that risk factor is a proxy for need'- indicating the need for need'- indicating the need for

promotive and preventive health promotive and preventive health services.services.

Prominent Risk FactorsProminent Risk FactorsDiseasesDiseases Risk FactorsRisk Factors

Heart diseaseHeart disease Smoking, high blood Pressure, elevated Smoking, high blood Pressure, elevated serum cholesterol, diabetes, obesity, lack of serum cholesterol, diabetes, obesity, lack of exercise, type A personalityexercise, type A personality

CancerCancer Smoking, alcohol, solar radiation, ionizing Smoking, alcohol, solar radiation, ionizing radiation, work-site hazards, environmental radiation, work-site hazards, environmental pollution, medications, infectious agents, pollution, medications, infectious agents, dietary factors.dietary factors.

StrokeStroke High blood pressure, elevated cholesterol, High blood pressure, elevated cholesterol, smoking.smoking.

Motor vehicle Motor vehicle accidentsaccidents

Alcohol, non-use of seat belts, speed, Alcohol, non-use of seat belts, speed, automobile design, roadway designautomobile design, roadway design

DiabetesDiabetes Obesity, dietObesity, diet

Cirrhosis of liverCirrhosis of liver AlcoholAlcohol

““AT RISK GROUPS”AT RISK GROUPS”

Biological situation:Biological situation:

- - ageage: infants (low birth weight), toddlers, elderly: infants (low birth weight), toddlers, elderly

- - sex:sex: females in the reproductive age period females in the reproductive age period

- - physiological state:physiological state: pregnancy, cholesterol level, high pregnancy, cholesterol level, high

blood pressureblood pressure

- - genetic factors : genetic factors : family history of genetic disordersfamily history of genetic disorders

- - others:others: disease, physical functioning, unhealthy behavior disease, physical functioning, unhealthy behavior

Physical situation:Physical situation:

- rural, urban slums- rural, urban slums

- living conditions, overcrowding- living conditions, overcrowding

- environment: water supply, proximity to industries - environment: water supply, proximity to industries

““AT RISK GROUPS”AT RISK GROUPS”

Sociocultural situation:Sociocultural situation:

- social class- social class

- ethnic and cultural group- ethnic and cultural group

- family disruption, education, housing- family disruption, education, housing

- customs, habits and behaviour like - customs, habits and behaviour like

smoking, lack of exercise, over-eating, smoking, lack of exercise, over-eating,

drug addicts)drug addicts)

- access to health services- access to health services

- lifestyles and attitudes- lifestyles and attitudes

Disease ControlDisease ControlAn ongoing operation to reduce:An ongoing operation to reduce:

i. The incidence of diseasei. The incidence of diseaseii. The duration of diseaseii. The duration of disease

iii. The risk of transmission.iii. The risk of transmission.iv. The effects of infection, including both the iv. The effects of infection, including both the physical and psychosocial complicationsphysical and psychosocial complicationsv. The financial burden to the community.v. The financial burden to the community.

The disease “agent” is permitted to persist in theThe disease “agent” is permitted to persist in thecommunity at a level where it ceases to be acommunity at a level where it ceases to be apublic health problempublic health problem..

Disease EliminationDisease Elimination

Between control and eradication.Between control and eradication.

Elimination is used to describe Elimination is used to describe interruption of transmission of interruption of transmission of disease from large geographic disease from large geographic regions or areas.regions or areas.

Disease Eradication Disease Eradication

Termination of all transmission of Termination of all transmission of infection by extermination of the infection by extermination of the infectious agent from the whole infectious agent from the whole world.world.

Eradication is an absolute process.Eradication is an absolute process.It is all or none phenomenon.It is all or none phenomenon.

MonitoringMonitoring

The performance and analysis of routine The performance and analysis of routine measurements aimed at detecting measurements aimed at detecting changes in the environment or health changes in the environment or health status of population.status of population.

The continuous oversight of activities to The continuous oversight of activities to ensure that they are proceeding ensure that they are proceeding according to plan.according to plan.

SurveillanceSurveillanceThe continuous scrutiny of the The continuous scrutiny of the

factors that determine the factors that determine the occurrence and distribution of occurrence and distribution of disease and other conditions of ill – disease and other conditions of ill – health. It includes the collection, health. It includes the collection, analysis, interpretation and analysis, interpretation and distribution of relevant data for distribution of relevant data for actionaction

ObjectivesObjectives

•To provide information about To provide information about new and changing h. problemsnew and changing h. problems•To provide feed-back which may To provide feed-back which may be expected to modify the policy be expected to modify the policy and redefine objectives.and redefine objectives.• Provide timely warning of public Provide timely warning of public health disasters so that health disasters so that interventions can be mobilizedinterventions can be mobilized

Iceberg of diseaseIceberg of disease

LEVELS OF PREVENTIONLEVELS OF PREVENTION

1. 1. Primordial PreventionPrimordial Prevention

Prevention of emergence or development Prevention of emergence or development of risk factors in country or population of risk factors in country or population groups in which they have not yet been groups in which they have not yet been appeared.appeared.

Discourage to adapt harmful lifestyle.Discourage to adapt harmful lifestyle.

THROUGH:THROUGH: Individual education Individual education

Mass educationMass education..

2. PRIMARY PREVENTION2. PRIMARY PREVENTION

An action taken prior to the onset of disease, An action taken prior to the onset of disease, which removes the possibility that disease will which removes the possibility that disease will occur.occur.

Intervention in the pre-pathogenesis phase of a Intervention in the pre-pathogenesis phase of a disease or H. problem, disease or H. problem,

To promote general health To promote general health To promote quality of lifeTo promote quality of life By By 1: adapting specific measures.1: adapting specific measures.

2: Elimination/modification of risk factors2: Elimination/modification of risk factorsSTRATEGY: STRATEGY: Population & High riskPopulation & High risk

3.SECONDARY PREVENTION3.SECONDARY PREVENTION

Action which halts the progress of a disease at its Action which halts the progress of a disease at its incipient stage and prevents complications.incipient stage and prevents complications.

Early Diagnosis &Early Diagnosis &

Adequate treatment.Adequate treatment.

To arrest the disease processTo arrest the disease process

Restore health by seeking unrecognized diseaseRestore health by seeking unrecognized disease

Prompt treatment before irreversible changes occurPrompt treatment before irreversible changes occur

Reverse communicabilty of infectious disease.Reverse communicabilty of infectious disease.

4. TERTIARY PREVENTION4. TERTIARY PREVENTION

All measures available to reduce or limit All measures available to reduce or limit impairment and disabilities, minimize impairment and disabilities, minimize sufferings and promote patient’s sufferings and promote patient’s adjustment to irremediable conditions.adjustment to irremediable conditions.

intervention in late pathogenesisintervention in late pathogenesis Intervention to limit disabilityIntervention to limit disability

MODES OF INTERVENTIONMODES OF INTERVENTION

Any attempt to intervene or interrupt the Any attempt to intervene or interrupt the usual sequence in the development of usual sequence in the development of disease in man.disease in man.

1.1. Health promotionHealth promotion2.2. Specific protectionSpecific protection3.3. Early diagnosis & prompt treatmentEarly diagnosis & prompt treatment4.4. Disability LimitationDisability Limitation5.5. Rehabilitation.Rehabilitation.

1.HEALTH PROMOTION1.HEALTH PROMOTION

A process of enabling people to A process of enabling people to increase control over & to improve increase control over & to improve health.health.

Health educationHealth education Environmental modificationsEnvironmental modifications Nutritional interventionsNutritional interventions Life style & behavioural changesLife style & behavioural changes

HEALTH PROMOTIONHEALTH PROMOTION Health educationHealth education Good standard of nutritionGood standard of nutrition Attention to personality developmentAttention to personality development Provision of good housing & recreationProvision of good housing & recreation Good working conditionsGood working conditions Marriage counselingMarriage counseling Sex educationSex education Periodic selective examinationsPeriodic selective examinations GeneticsGenetics Environmental modificationsEnvironmental modifications

2.SPECIFIC PROTECTION2.SPECIFIC PROTECTION USE OF SPECIFIC IMMUNIZATIONSUSE OF SPECIFIC IMMUNIZATIONS USE OF SPECIFIC NUTRIENTSUSE OF SPECIFIC NUTRIENTS CHEMOPROPHYLAXISCHEMOPROPHYLAXIS PROTECTION AGAINST OCCUP.HAZARDSPROTECTION AGAINST OCCUP.HAZARDS PROTECTION FROM CARCINOGENSPROTECTION FROM CARCINOGENS AVOIDANCE OF ALLERGENSAVOIDANCE OF ALLERGENS USE OF ENVIRONMENTAL SANITATIONUSE OF ENVIRONMENTAL SANITATION CONTROL OF QUALITY PRODUCTSCONTROL OF QUALITY PRODUCTS PROTECTION FROM ACCIDENTSPROTECTION FROM ACCIDENTS ATTENTION TO PERSONAL HYGIENEATTENTION TO PERSONAL HYGIENE

3.EARLY DIAGNOSIS & PROMPT 3.EARLY DIAGNOSIS & PROMPT TRAETMENTTRAETMENT

To intercept the disease processTo intercept the disease process To cure and prevent disease processTo cure and prevent disease process To prevent secondary cases (spread)To prevent secondary cases (spread) To prevent complications and sequelaeTo prevent complications and sequelae To shorten period of disabilityTo shorten period of disability To reduce mortalityTo reduce mortality For better prognosisFor better prognosis

(Critically important in chronic diseases)(Critically important in chronic diseases)

3.EARLY DIAGNOSIS & PROMPT 3.EARLY DIAGNOSIS & PROMPT TRAETMENTTRAETMENT

Case finding measuresCase finding measures Screening surveysScreening surveys Selective examinationsSelective examinations Mass treatment approachMass treatment approach

Total mass approachTotal mass approach

Juvenile mass treatmentJuvenile mass treatment

selective mass treatmentselective mass treatment

Disability limitationDisability limitation

To prevent or halt the transition of the To prevent or halt the transition of the disease process from impairment to disease process from impairment to handicaphandicap..

Adequate treatment to arrest disease processAdequate treatment to arrest disease process To prevent further complications/disabilityTo prevent further complications/disability Provision of facilities to limit disability and to Provision of facilities to limit disability and to

prevent death.prevent death.

Disease Disease → Impairment → Disability → Handicap→ Impairment → Disability → Handicap

IMPAIRMENT:IMPAIRMENT:

Any loss or abnormality of psychological, Any loss or abnormality of psychological, physiological or anatomical structure or function.physiological or anatomical structure or function.e.g. Loss of foote.g. Loss of foot

Defective visionDefective visionMental retardationMental retardation

IMPAIRMENTIMPAIRMENTvisible or invisiblevisible or invisibleTemporary or permanentTemporary or permanentProgressive or regressiveProgressive or regressive

DISABILITYDISABILITY

Inability to carry out certain activitiesInability to carry out certain activities

““Any restriction or lack of ability to performAny restriction or lack of ability to perform

an activity within the range considered an activity within the range considered normal for a human being”.normal for a human being”.

HANDICAPHANDICAP

A disadvantage for a given A disadvantage for a given individual, resulting from an individual, resulting from an impairment or a disability, that impairment or a disability, that

limits or prevents the fulfillment limits or prevents the fulfillment

of a role that is normal for that of a role that is normal for that individual (depending on age, sex, individual (depending on age, sex, and social and cultural factors).and social and cultural factors).

Concept of disabilityConcept of disability

AccidentAccident DiseaseDisease Loss of footLoss of foot ImpairmentImpairment Cannot walkCannot walk DisabilityDisability UnemployedUnemployed HandicapHandicap

REHABILITATIONREHABILITATION

The combined and coordinated The combined and coordinated use of medical, social, use of medical, social, educational and vocational educational and vocational measures for training and measures for training and retraining the individual to the retraining the individual to the highest possible level of highest possible level of functional ability. functional ability.

RehabilitationRehabilitation

a.a. Medical rehabilitation – restoration of functionMedical rehabilitation – restoration of function

b.b. Vocational rehabilitation – restoration of the Vocational rehabilitation – restoration of the capacity to earn a livelihood.capacity to earn a livelihood.

c.c. Social rehabilitation – restoration of family and Social rehabilitation – restoration of family and social relationshipssocial relationships

d.d. Psychological rehabilitation – restoration of Psychological rehabilitation – restoration of personal dignity and confidence.personal dignity and confidence.

““to live and work within the limits of disability to live and work within the limits of disability but to his capacitybut to his capacity”.”.

RehabilitationRehabilitation Establishing schools for blindEstablishing schools for blind Provision of aids for crippledProvision of aids for crippled Reconstructive surgery Reconstructive surgery Community facilities to retrain disabled to use Community facilities to retrain disabled to use

remaining capacitiesremaining capacities Graded exercisesGraded exercises Changes in professionChanges in profession Modification of life & full employment as possibleModification of life & full employment as possible Education of industry to utilize rehabilitatedEducation of industry to utilize rehabilitated Use of sheltered colonyUse of sheltered colony

Thank you

INFECTIONINFECTION

The entry and development or The entry and development or multiplication of an infectious agent in the multiplication of an infectious agent in the body of man or animals. An infection body of man or animals. An infection does not always cause illness.does not always cause illness.Body responds asBody responds as -immune response-immune response

-disease-disease. .

CONTAMINATIONCONTAMINATION

The presence of an infectious agent on a The presence of an infectious agent on a body surface; also on or in clothes, body surface; also on or in clothes, beddings, toys, surgical instruments or beddings, toys, surgical instruments or dressings, or other inanimate articles or dressings, or other inanimate articles or substances including water, milk and substances including water, milk and food.food.

POLLUTIONPOLLUTION

The presence of offensive material is called pollution. It is distinct from contamination. .

INFESTATIONINFESTATION

It is a state of having a parasite in or on It is a state of having a parasite in or on the body which includes arthropods or the body which includes arthropods or animal parasites. The lodgement, animal parasites. The lodgement, development and reproduction of development and reproduction of arthropods on the surface of the body of arthropods on the surface of the body of man or animal, in the clothings etc.man or animal, in the clothings etc.

HOSTHOST A person or animal that affords subsistence or A person or animal that affords subsistence or

lodgement of an infectious agent under natural lodgement of an infectious agent under natural conditions.conditions.

An An obligateobligate host: means the only host. host: means the only host. An An intermediateintermediate host: in which the parasite is host: in which the parasite is

in a larval or asexual state. (Secondary))in a larval or asexual state. (Secondary)) DefinitiveDefinitive Host: in which the parasite attains Host: in which the parasite attains

maturity or passes its sexual stage. (Primary) maturity or passes its sexual stage. (Primary) A A transporttransport host: a carrier in which the host: a carrier in which the

organism remains alive but does not undergo organism remains alive but does not undergo development.development.

INFECTIOUS DISEASEINFECTIOUS DISEASE

A clinically manifest disease of man or A clinically manifest disease of man or animal that results from an infection.animal that results from an infection.

It is a state of disorder that results from It is a state of disorder that results from an infection by bacteria or viruses. an infection by bacteria or viruses.

e.g., cholera, Diphtheria, Tuberculosis, e.g., cholera, Diphtheria, Tuberculosis, measles, Chickenpox.measles, Chickenpox.

CONTAGIOUS DISEASECONTAGIOUS DISEASE

A disease that is transmitted through A disease that is transmitted through contact. contact.

e.g. scabies, trachoma, STD and e.g. scabies, trachoma, STD and leprosy.leprosy.

COMMUNICABLE DISEASECOMMUNICABLE DISEASE

An illness due to a specific An illness due to a specific infectious agent or its toxic products infectious agent or its toxic products capable of being transmitted directly capable of being transmitted directly or indirectly from man to man , or indirectly from man to man , animal to animal or from animal to animal or from environment to man or animal. environment to man or animal.

EPIDEMICEPIDEMIC

Unusual occurrence of a disease or Unusual occurrence of a disease or health related problem and health related health related problem and health related behaviour in a community or region behaviour in a community or region clearly in excess of expected occurrence.clearly in excess of expected occurrence.

..

Disease affecting a large number of Disease affecting a large number of persons within a short space of time.persons within a short space of time.

ENDEMIC ENDEMIC

It refers to the constant presence of a disease It refers to the constant presence of a disease or an infectious agent within a given or an infectious agent within a given geographic area or population group.geographic area or population group.

When the number of susceptible and immune When the number of susceptible and immune persons are almost equal, the disease persons are almost equal, the disease continues to smoulder in a community and is continues to smoulder in a community and is always present in the community.always present in the community.

HYPERENDEMICHYPERENDEMIC It expresses that the disease is It expresses that the disease is

constantly present at a high constantly present at a high incidence or prevalence and incidence or prevalence and affects all age groups equally.affects all age groups equally.

HOLOENDEMICHOLOENDEMIC

It is the high level of infection It is the high level of infection beginning in early life and beginning in early life and affecting most of the child affecting most of the child population.population.

SPORADICSPORADIC

The cases occur irregularly, haphazardly The cases occur irregularly, haphazardly from time to time and generally from time to time and generally infrequently.infrequently.

The cases are so few and separated that The cases are so few and separated that they show little or no connection with they show little or no connection with each other nor a common source of each other nor a common source of infection.infection.

PANDEMIC PANDEMIC

An epidemic usually affecting a large An epidemic usually affecting a large proportion of the population, occurring proportion of the population, occurring over a large geographic area such as over a large geographic area such as nation, continent or the whole world.nation, continent or the whole world.

A world wide epidemic is a pandemic.A world wide epidemic is a pandemic.

When the susceptibility of the whole When the susceptibility of the whole country or the world is increased for a country or the world is increased for a particular organism e.g. influenza particular organism e.g. influenza Pandemic of 1918-19.Pandemic of 1918-19.

EXOTICEXOTIC

When a disease is not usually When a disease is not usually present in a locality but is introduced present in a locality but is introduced form abroad, it is called Exoticform abroad, it is called Exotic..

ZOONOSISZOONOSIS

An infection or infectious disease An infection or infectious disease transmissible under normal conditions transmissible under normal conditions from vertebrate animals to man.from vertebrate animals to man.

e.g. rabies, plague, bovine tuberculosis,e.g. rabies, plague, bovine tuberculosis,

Anthrax, brucellosis, endemic typhus etc.Anthrax, brucellosis, endemic typhus etc.

EPIZOOTICEPIZOOTIC

An outbreak ( epidemic) of disease in an An outbreak ( epidemic) of disease in an animal population.animal population.

e.g. anthrax, brucellosis, rabies.e.g. anthrax, brucellosis, rabies.

NOSOCOMIAL INFECTIONNOSOCOMIAL INFECTION

Hospital acquiredHospital acquired An infection originating in a patient while in a An infection originating in a patient while in a

hospital or health care facility.hospital or health care facility. A disorder associated with being in a hospital.A disorder associated with being in a hospital. It may be unrelated with the primary condition.It may be unrelated with the primary condition. May appear after discharge.May appear after discharge. Infections to the staff of the facility.Infections to the staff of the facility.

OPPORTUNISTIC INFECTIONOPPORTUNISTIC INFECTION

It is an infection by an organism that It is an infection by an organism that takes the opportunity provided by the takes the opportunity provided by the defect in host defense to infect the host defect in host defense to infect the host and cause disease.and cause disease.

Opportunistic infections are common in Opportunistic infections are common in AIDSAIDS

E.g. Herpes, E.g. Herpes, cytomegalovirus,toxoplasmacytomegalovirus,toxoplasma

IATROGENIC DISEASEIATROGENIC DISEASE

Physician induced diseasePhysician induced disease An adverse consequence of a preventive, An adverse consequence of a preventive,

diagnostic or therapeutic regimen or procedure diagnostic or therapeutic regimen or procedure that causes impairment, handicap, disability or that causes impairment, handicap, disability or death resulting from a physician’s professional death resulting from a physician’s professional activity.activity.

Can prolong hospital stayCan prolong hospital stay Requires special treatmentRequires special treatment Threaten life.Threaten life.

HOSTHOST A person or animal that affords subsistence or A person or animal that affords subsistence or

lodgement of an infectious agent under natural lodgement of an infectious agent under natural conditions.conditions.

An An obligateobligate host: means the only host. host: means the only host. An An intermediateintermediate host: in which the parasite is host: in which the parasite is

in a larval or asexual state. (Secondary))in a larval or asexual state. (Secondary)) DefinitiveDefinitive Host: in which the parasite attains Host: in which the parasite attains

maturity or passes its sexual stage. (Primary) maturity or passes its sexual stage. (Primary) A A transporttransport host: a carrier in which the host: a carrier in which the

organism remains alive but does not undergo organism remains alive but does not undergo development.development.

RESERVOIRRESERVOIR

Any person, animal, soil, arthropod, plant Any person, animal, soil, arthropod, plant or substance in which an infectious agent or substance in which an infectious agent lives and multiplies, on which depends lives and multiplies, on which depends primarily for survival and can be primarily for survival and can be transmitted to a susceptible host.transmitted to a susceptible host.

Reservoir is a natural habitat in which an Reservoir is a natural habitat in which an organism metabolises and replicates.organism metabolises and replicates.

SOURCESOURCE A PERSON, ANIMAL, OBJECT, OR A PERSON, ANIMAL, OBJECT, OR

SUBSTANCE FROM WHICH AN SUBSTANCE FROM WHICH AN INFECTIOUS AGENT PASSES OR INFECTIOUS AGENT PASSES OR IS DESSIMINATED TO THE HOST.IS DESSIMINATED TO THE HOST.

HUMAN RESERVOIRHUMAN RESERVOIR

CASES:CASES:

A person in the population or study group A person in the population or study group identified as having the particular disease, identified as having the particular disease, health disorder or condition under health disorder or condition under investigation.investigation.

clinical, biochemical, laboratory testsclinical, biochemical, laboratory tests Clinical casesClinical cases Sub clinical casesSub clinical cases Latent infectionLatent infection: host does not shed : host does not shed

infectious agent which lies dormant within the infectious agent which lies dormant within the host without symptoms. host without symptoms.

HUMAN RESERVOIRHUMAN RESERVOIR

CARRIER:CARRIER: An infected person or animal that An infected person or animal that

harbours a specific infectious agent in the harbours a specific infectious agent in the absence of discernible clinical disease absence of discernible clinical disease and serves as a potential source of and serves as a potential source of infection for others.infection for others.

Carriers are less infectiousCarriers are less infectious Carriers are more dangerous than cases.Carriers are more dangerous than cases.

CARRIERCARRIERA TypeA Type

(a) Incubatory(a) Incubatory(b) Convalescent(b) Convalescent( c) Healthy( c) Healthy

B DurationB Duration(a) Temporary(a) Temporary(b) Chronic(b) Chronic

C Portal of ExitC Portal of Exit(a) Urinary(a) Urinary(b) Intestinal (b) Intestinal (c) Respiratory(c) Respiratory

MODES OF TRANSMISSION

DIRECT TRANSMISSIONDIRECT TRANSMISSION

1.1. Direct ContactDirect Contact

2.2. Droplet InfectionDroplet Infection

3.3. Contact with soilContact with soil

4.4. Inoculation into skin or mucosaInoculation into skin or mucosa

5.5. Transplacental (vertical)Transplacental (vertical)

INDIRECT TRANSMISSIONINDIRECT TRANSMISSION

1. Vehicle-borne (water, food, milk, fruits)1. Vehicle-borne (water, food, milk, fruits)

2. Vector-borne2. Vector-borne

a Mechanical Transmissiona Mechanical Transmission

b Biological Transmissionb Biological Transmission

i. Propagative i. Propagative

ii. Cyclo – Propagativeii. Cyclo – Propagative

iii. Cyclo Developmentaliii. Cyclo Developmental

INDIRECT TRANSMISSIONINDIRECT TRANSMISSION

3. Air – Borne3. Air – Borne

a Droplet nucleia Droplet nuclei

b Dustb Dust

4. Fomite – borne4. Fomite – borne

5. Unclean hands and fingers5. Unclean hands and fingers

Incubation PeriodIncubation Period

The time interval between invasion by The time interval between invasion by an infectious agent and appearance an infectious agent and appearance of the first sign or symptom of the of the first sign or symptom of the disease.disease.

Median Incubation PeriodMedian Incubation Period::

The time required for 50 per cent of The time required for 50 per cent of the cases to occur following exposure.the cases to occur following exposure...

USES OF INCUBATION PERIODUSES OF INCUBATION PERIOD

a. Tracing the source of infection and a. Tracing the source of infection and contactscontacts

b. Period of Surveillanceb. Period of Surveillance

c. Immunizationc. Immunization

d. Identification of point source or d. Identification of point source or propagated epidemicspropagated epidemics

e. Prognosise. Prognosis

Thank you