Kapita Selekta Epidemiologi

Dr. Efyluk Garianto, M.Kes

Epidemiology Comes from Greek words

epi, meaning on or upon demos,meaning people logos, meaning the study of

Study of distribution and determinants of health-related conditions or events in populations

Ilmu yang mempelajari distribusi dan faktor-faktor penentu dari suatu kondisi atau kejadianyg berkaitan dengan kesehatan pd suatu populasi

Distribusi penyakit/masalah kesehatan

Menurut orang (umur, jenis kelamin, ras, status sosial, dll

Menurut tempat (Desa, kota, pesisir, pegunungan, sekolah, asrama, LP, tempatlahir, RS, dll)

Menurut waktu (hari, bulan, tahun, musim, dll)

Common Terms

Descriptive Epidemiology

organize and summarize data according to time, place, and person Time disease rates change over time the

seasonal increase in influenza with the onset of cold weather

time data is usually shown on a graph

Place - describe a health event by place to gain insight into the geographical extent of the problem. Residence Birthplace place of employment school district hospital unit, etc

Person

inherent characteristics of people Age Race Sex

Causation

cause of disease is a factor (characteristic, behavior, event, etc.) that influences the occurrence of disease An increase in the factors leads to an

increase in disease. Reduction of the factors leads to a reduction

in disease

Epidemiologic triangle

traditional model of infectious disease causation.

AgentAgent

HostHost EnvironmentEnvironment

Agent

Infectious microorganism - must be present for disease to occur Virus Bacterium Parasite other microbe

AgentAgent

HostHost EnvironmentEnvironment

Host factors

Intrinsic factors that influence an individuals exposure, susceptibility, or response to a causative agent. Age Race Sex socioeconomic status behaviors

AgentAgent

HostHost EnvironmentEnvironment

Environmental factors

Extrinsic factors which affect the agent and the opportunity for exposure

physical factors biologic factors socioeconomic factors

AgentAgent

HostHost EnvironmentEnvironment

Epidemiology and Disease

Chain of Infection

ReservoirReservoir

Mode of Mode of TransmissionTransmission

Susceptible Susceptible HostHost

Mode of Mode of TransmissionTransmission

Chain of Infection

reservoir of an agent is the habitat in which an infectious agent normally lives, grows, and multiplies.

Portal of Entry is the path by which an agent enters a susceptible host

Portal of exit is the path by which an agent leaves the source host

Pat

hoge

n R

eser

voirs

Humans are the most important reservoir of human infectious disease.

Por

tals

of E

xit

Por

tals

of E

ntry

Por

tals

of E

ntry Many

organisms that cause one disease if they enter one body site are harmless if they enter another, e.g., various enteric urinary-tract pathogens.

Chain of Infection Modes of transmission

Direct immediate transfer of the agent from a reservoir to a susceptible host by direct contact or droplet spread

Direct contact Droplet spread

Indirect an agent is carried from a reservoir to a susceptible host by suspended air particles or by animate (vector) or inanimate (vehicle) intermediaries

Airborne Vehicleborne Vectorborne Mechanical

Biologic

Mod

es o

f Tra

nsm

issi

on

Chain of Infection

Portal of entry means by which an agent enters a susceptible host

Host individual infected with the agent

Epidemic Disease Occurrence Level of Disease - amount of a particular

disease that is usually present in a community

SporadicSporadic

EndemicEndemic

EpidemicEpidemic

PandemicPandemicIncreasing amount of diseaseIncreasing amount of disease

Sporadic - irregular pattern of occurrence, with occasional cases occurring at irregular intervals

Endemic - persistent level of occurrence with a low to moderate disease level

Epidemic or Outbreak- occurrence of a disease within an area is clearly in excess of the expected level for a given time period

Pandemic - an epidemic spreads over several countries or continents, affecting a large number of people

Pat

hoge

n Tr

ansm

issi

on

ZoonosesZoonoses are Human Diseases with Animal Reservoirs.

ZoonosesToxoplasmosis

Contact Transmission

Rhinovirus?

Dire

ct-C

onta

ct T

rans

mis

sion

Dire

ct F

ecal

-Ora

l Tra

nsm

issi

on

Giardiasis in daycare centers.

Indirect-Contact Transmission

Beddings are an example of a Fomite, an inanimate object that can transmit pathogens between people.

Methicillin-resistant Staphylococcus aurius(MRSA)?

Indirect-Contact Transmission

Door knobs are another good example of a fomite.

Influenza virus?

Droplet Transmission

Measles?

Airborne Transmission

Mycobacterium tuberculosis?

Airborne Transmission

Contact with air from small room containing 12 people.

Contact with air from clean, empty room.

Wat

erbo

rne

Tran

smis

sion

Cryptosporidium parvum?

Wat

erbo

rne

Tran

smis

sion

Giardiasis from water.

Food

born

e Tr

ansm

issi

on

Hepatitis A

Food

born

e Tr

ansm

issi

on

Balantidium coli

Types of Epidemiological Studies

Type

s of

Epi

dem

iolo

gcal

Stu

dies q Descriptive studies are simply those that describe the

events and rates of disease. They tend to be the first sets of studies done. Quoted or paraphrased from http://dante.med.utoronto.ca/doch/Year1/EPIModule/Part6a.htm

q Observational/Analytical studies then look towards finding out the causes of the observed rates. They are called "observational" since the epidemiologist does not intervene in the assignment of exposure.

q Experimental studies are formal research experiments. The classic example is the randomized control trial where one group is randomly assigned a treatment and a control group gets the placebo or "usual" treatment.

q Experimental studies are expensive and test a very specific question. Usually a great deal of descriptive and observational studies are done first.