Pengendalian dan pemberantasan penyakit5-6/2014
DISIAPKAN OLEH PROF. DR.DRH.PRATIWI, TS. MS
DRH.ROSITAWATI, I. MP
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OUTBREAK
INVESTIGATIO
N
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Definition Outbreak investigation purposes The pattern of temporal, spatial and animals
10 steps outbreak investigation
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Definitions
Occurrence of more cases of disease than expected : - in a given area - among a specific group of population- over a particular period of time
What is an outbreak ?
Outbreak Epidemiology- Study of a disease cluster or epidemic
in order to control or prevent further spread of the disease in the population.
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PENGENDALIAN BERDASARKAN PERWILAYAHAN (ZONING)
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DAERAH TERTULAR: daerah yang sudah dinyatakan ada kasus secara klinis, PA dan HP serta dikonfirmasi dgn hasil laboratorium
DAERAH TERANCAM: daerah yang berbatasan langsung dengan daerah tertular atau tidak memiliki batasan alam dengan daerah tertular
DAERAH BEBAS: daerah yang dinyatakan masih belum ada kasus secara klinis, PA dan HP atau memiliki batasan alam (propinsi, pulau)
SISTEM KEWASPADAAN DINI(EARLY WARNING SYSTEM)
SUBSISTEM KESIAGAAN DINI - PENGAMATAN DINI - PENANGGULANGAN DINI
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SISTEM KEWASPADAAN DINI(EARLY WARNING SYSTEM)
SUBSISTEM PERAMALAN WABAH - PREDIKSI KEJADIAN WABAH - TINDAKAN ANTISIPASI
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Outbreaks
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2 or more cases associated in time and place
E. coli 0157:H7 (Northwest) Cryptosporidium (Milwaukee) Norwalk virus (Cruise ships) Vibrio cholerae (South America) Listeria (New York, New Jersey, CT)
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What is infectious disease epidemiology?
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Epidemiology Deals with one population Risk case Identifies causes
Infectious disease epidemiology Two or more populations A case is a risk factor The cause often known
(www)02/05/2012
Agents
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Clostridium botulinum, C. perfringens Staphylococci, Salmonella, Shigella Campylobacter jejuni, E. coli 0157:H7 Vibrio parahaemolyticus Hepatitis A, Norwalk virus, Rotavirus Calicivirus, Listeria monocytogenes Cryptosporidium, Giardia, Bacillus
cereus Toxoplasma gondii, Cyclospora
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Food borne Diseases
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Infection◦ long incubation
period (days)◦ diarrhea, nausea,
vomiting, abdominal cramps. Fever often
◦ Salmonella, ◦ Hepatitis A◦ Listeria, Giardia◦ Vibrio,
Campylobacter◦ Norwalk virus
Intoxication◦ short incubation
period (minutes - hours)
◦ Vomiting, nausea, double vision, weakness, numbness, disorientation
◦ C. botulinum◦ Staph aureus◦ certain fish/ shellfish
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Natural Barriers to Infection
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Stomach acid pH 2 GI Tract immune system Normal intestinal flora Bile acids and digestive enzymes
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Increased Susceptibility
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Gastrectomy acid blockers for ulcers antacids, excessive consumption of water buffering capacity of food- milk, fatty foods antibiotic therapy very young, old immunocompromised stress, poor hygiene, underdeveloped areas
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Retrospective investigation
• Often the outbreak exists since days, weeks,months
• Many cases already occurred • Count on the memory of people• Many data already collected; use them or start all
over?
Never too late, but more difficult
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1) Establish the existence of an outbreak2) Confirm the diagnosis3) Define a case and count cases4) Perform descriptive epidemiology
(person, place and time)5) Determine who is at risk6) Develop hypotheses explaining exposure
& disease
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Steps in Investigating an Outbreak
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7) Evaluate hypotheses8) As necessary, reconsider/refine
hypotheses and execute additional studies– additional epidemiologic studies– other types of studies – laboratory,
environmental
9) Communicate findings – written report– presentations
10) Implement control and prevention measures
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Steps in Investigating an Outbreak
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Definition of outbreak• One case – for diseases of epidemic potential (e.g., measles, cholera)
• More than the expected number of cases – for endemic diseases
• Sometimes is quantitative threshold (e.g.meningococcal meningitis)
Importance of a good surveillance system for early warning
Confirm the Existence of an Outbreak
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• Determine whether there is an outbreak – an excess number of cases from what would be expected
• Establish a case definition – Non-ambiguous– Clinical / diagnostic verification– Person / place / time descriptions
• Identify and count cases of illness
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Verify the outbreak
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• Graph of the number of cases (y-axis) by their date or time of onset (x-axis)
• Interpreting an epidemic curve– Overall pattern: increase, peak,
decrease• Type of epidemic?• Incubation period?
– Outliers: • Unrelated? • Early or late exposure? • Index case? Secondary cases?
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Plot an Epidemic Curve
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Endemic vs. Epidemic
Endemic Epidemic
No.
of
Cas
es o
f a
Dis
ease
Time
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• Starts slowly• Time between the first case and the peak is comparable
to the incubation period. • Slow tail
Vector-borne Disease
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• This is the most common form of transmission in food-borne disease, in which a large population is exposed for a short period of time.
Point Source Transmission
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• In this case, there are several peaks, and the incubation period cannot be identified.
Continuing Common Source or Intermittent Exposure
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TIME, PLACE, PERSON May be possible to answer:
◦ Who is at risk?◦ What is source of infection?◦ What is mode of transmission?
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Descriptive Epidemiology
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• Distribution of cases by date of onset
• X axis: time Y axis: number of cases
• Shows:– Time limits / duration of the outbreak– Peak / incubation period– Form of curve: evolution of outbreak– Formulate hypothesis regarding source
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Descriptive Epidemiology - Time
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Cycle of Foodborne Disease Control and Prevention
Surveillance
Epidemiologic Investigation
AppliedResearch
Prevention Measures
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Talk with health workers Examine cases yourself ! Laboratory testing (e.g., malaria, cholera,
hemorrhagic fevers, etc.)
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Confirm the Diagnosis
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Epidemiologic Curve
0
2
4
6
8
10
12
1 2 3 4 5 6 7 8 9
Date
Nu
mb
er
of
cases
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Control of present outbreak
Prevention of future similar outbreaks
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Recommend control measures
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Numerators◦ Describe cases in terms of
age, sex, other parameters : refugee / displaced / residents immunized , not immunized
Denominators◦ Distribution in the overall population (age, sex,...)
Compare rates to identify high risk groups
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Descriptive Epidemiology - Person
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Map cases: identify geographic places at risk
Determine where disease acquired: Home, work, travel, etc..
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Descriptive Epidemiology - Place
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Personal information• Age• Sex• Place of residence (address)• Other relevant “exposures”
– Refugees vs locals– Food source– Water source
• Ethnicity, religion, etc.
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Information to Collect on Cases
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Disease data Date of onset of symptoms Clinical symptoms and signs Immunized or not (measles, meningitis) Laboratory results (if any) Duration of disease, outcome (death,
cured,..) Treatment received
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Information to Collect on Cases
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Often obvious from descriptive epidemiology
Formulate idea about source of outbreak and mode of transmission
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Develop Hypotheses
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• Cross – sectional study?• Cohort study • Case – control study
– Identify cases– Select control group
• Possibly matched on age or sex or location• Community control, clinic control etc.
– Compare exposures among cases and controls– Calculate odds for various exposures
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Test Hypotheses
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Clarifies your own ideas / synthesis Presents data and conclusions to anyone
interested◦ Often epidemiologist don’t implement
interventions◦ Must communicate to those who will intervene
Advocacy: MOH, UN, other NGOs, donors Basis for future reference
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Write a Report
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Interventions include Prevention of further cases Control of transmission and source of
infection Improve case management, lower case-
fatality rate
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Implement - Take ACTION
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Terimakasih Selamat Belajar
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