IntroductioIntroduction n to to

EpidemioloEpidemiologygy

Sumattana.gSumattana.g@msu.ac.th@msu.ac.th

Concept of Epidemiolog Concept of Epidemiologyy

Epidemiology is the study of the occurrence, Epidemiology is the study of the occurrence, distribution and determinants distribution and determinants (which are (which are dynamic) dynamic) of health problems and diseases in of health problems and diseases in human populations or communities. The human populations or communities. The primary unit of concern is a group of persons, primary unit of concern is a group of persons, not any single person. Therefore, epidemiology not any single person. Therefore, epidemiology deals with population pathology, not clinical deals with population pathology, not clinical pathology (disease of a single person), nor pathology (disease of a single person), nor microscopic pathology (disease of a cell or microscopic pathology (disease of a cell or tissue). All population pathology relates back to tissue). All population pathology relates back to the community as the source of materials for the community as the source of materials for investigation and results from epidemiologic investigation and results from epidemiologic study study are interpreted in terms of the study study are interpreted in terms of the group, not individual.group, not individual.

Epidemiology for... Epidemiology for... Epidemic diseaseEpidemic disease PastPast Communicable diseaseCommunicable disease Non-communicable Non-communicable

diseasedisease Non-infectious diseaseNon-infectious disease

PresentPresent Chronic diseaseChronic disease Occupational diseaseOccupational disease Environmental diseaseEnvironmental disease

EPIDEMIOLOGEPIDEMIOLOGYY

EPIEPI == on, upon on, upon

DEMOSDEMOS = = people, population people, population

LOGOSLOGOS == knowledge, study knowledge, study

doctrine, discourse doctrine, discourse

sciencescience

Evolution of Definition Evolution of Definition The science or doctrine of epidemics The science or doctrine of epidemics

(New standard Dictionary of English La (New standard Dictionary of English Language)nguage)

The science of infective diseases, their The science of infective diseases, their prime causes, propagation and prevent prime causes, propagation and prevent

ionion

(Stallybrass)(Stallybrass) The study of conditions known or reaso The study of conditions known or reaso

nably supposed to influence the prevale nably supposed to influence the prevale nce of disease nce of disease

(Lumsden)(Lumsden)

Modern Meaning

Epidemiology is the science which concerns it Epidemiology is the science which concerns it self with the natural history of disease as it is self with the natural history of disease as it is

expressed in expressed in groups of persons groups of persons related by s related by s ome common factors of age, sex, race, locatio ome common factors of age, sex, race, locatio

n or occupation as distinct from the developm n or occupation as distinct from the developm ent of disease in an individual (American Epid ent of disease in an individual (American Epid

emiological Society) emiological Society) Epidemiology is the study of patterns of disea Epidemiology is the study of patterns of disea

se and the factors that cause se and the factors that cause disease in man disease in man (CDC)(CDC)

Epidemiology is the study of the distribution a Epidemiology is the study of the distribution a nd determinants of disease frequency nd determinants of disease frequency in man in man

(MacMahon & Pugh) (MacMahon & Pugh)

EpidemiologyEpidemiology

Epidemiology is the stud Epidemiology is the stud y of the y of the occurrence, dist occurrence, dist

ribution, determinants ribution, determinants (which are dynamic) (which are dynamic) of h of h

ealth problems and disea ealth problems and disea se se in human population in human population

s or communities s or communities

Aim an Purposes of Epidemiology

To describe and analyze disease To describe and analyze disease occurrences and distribution occurrences and distribution according to such variables as age, according to such variables as age, race, sex, occupation, temporal race, sex, occupation, temporal frequency of occurrence, periodic frequency of occurrence, periodic fluctuation, long term trends (time-fluctuation, long term trends (time-trend analysis) and geographic trend analysis) and geographic distribution, in order to make distribution, in order to make community diagnosis and to estimate community diagnosis and to estimate the morbidity and mortality risks. the morbidity and mortality risks.

Aim an Purposes of Epidemiology

To carefully analyze the To carefully analyze the characteristics and interactions of characteristics and interactions of agents, host and environmental agents, host and environmental factors in order to search for causes factors in order to search for causes ; determine all details of natural ; determine all details of natural history and preventive and control history and preventive and control measures ; and disclose gaps in measures ; and disclose gaps in knowledge.knowledge.

Aim an Purposes of Epidemiology

To improve medical care and provide To improve medical care and provide administrative guidance for administrative guidance for community health services.community health services.

To stimulate the use of systematic To stimulate the use of systematic approach of scientific research to approach of scientific research to study other problems in public health study other problems in public health related fields such as dentistry, related fields such as dentistry, welfare, education, administration welfare, education, administration and other important spheres.and other important spheres.

Scope and Content ofEpidemiology

Geographic PathologyGeographic Pathology Clinical EpidemiologyClinical Epidemiology Identification of Agents of DiseaseIdentification of Agents of Disease Statistical EpidemiologyStatistical Epidemiology Field Survey for Specific PurposesField Survey for Specific Purposes Incidence Study (Longitudinal Incidence Study (Longitudinal

Study)Study) Experimental EpidemiologyExperimental Epidemiology Tracing Reservoirs and Sources of Tracing Reservoirs and Sources of

InfectionInfection Administrative Control of DiseaseAdministrative Control of Disease

Epidemiological Team

Epidemiology is an applied science, at times it requires such divergent skill as those of physician, dentist, veterinarian, public health nurse, sanitarian, nutritionist, health educator, social worker, statistician, anthropologist, biochemist, meteorologist and others to work as a team.

Contributing F Contributing Factorsactors

AgentAgent AA HostHost HHEnvironmentEnvironment EE

Interaction of Interaction of A, H, E ; A, H, E ; Dr. John GordonDr. John Gordon

A H

EBalanc

e

Interaction of Interaction of A, H, E ; A, H, E ; Dr. John GordonDr. John Gordon

A

H

EAgent

changes

Interaction of Interaction of A, H, E ; A, H, E ; Dr. John GordonDr. John Gordon

A

HE

Host changes

Interaction of Interaction of A, H, E ; A, H, E ; Dr. John GordonDr. John Gordon

A

H

E

Environment changes facilitates agent spread

Interaction of Interaction of A, H, E ; A, H, E ; Dr. John GordonDr. John Gordon

A

H

E

Environment changes alters host susceptibility

Natural History of Disea se in man

2 Period 2 Period PPPPPPPPPPPPPPP PPPPPP PPPPPPPPPPPPPPP PPPPPP Pathogenesis Period Pathogenesis Period

- PPP PPPPPPPP PPPPP- PPP PPPPPPPP PPPPP- PPPPP P(- PPPPP P( Mild, Mild,

Moderate, Severe)Moderate, Severe)

- Disability- Disability

- Post interval eq- Post interval equillibriumuillibrium

Recovery or Recovery or CureCure Chronic StateChronic State Relapse Relapse DisabilityDisability Defect Defect Death Death