S3: Outbreak Investigation Flashcards
Def of Endemic
- Constant presence of a disease all over the year in certain area
Def of Epidemic
- Sudden appearance of a disease in certain area or in a specific time in excess of normal expectations based on past experience
Def of Outbreak
Localized epidemic
def of Pandemic
- Epidemic of a disease spread from one country to another in short time
OR
- a disease occurs at same time in different countries
Def of Sporadic
refers to a disease that occurs infrequently and irregularly.
Def of Outbreak in Details
Localized epidemic
In a given area
Over a particular period of time.
Among specific group of people
Objectives of investigation of an outbreak
❶ To define the magnitude
❷ To determine the particular conditions and factors responsible for the occurrence of the epidemic.
❸ To identify the cause, source of infection, and modes of transmission
❹ To formulate prevention and control measures
Steps of investigation of an outbreak
Summary
Steps of investigation of an outbreak
- Verification of diagnosis by clinical and labor Methods
**Example: In Case of Food Poisoning **
- Clinical diagnosis: cases show diarrhea, nausea, vomiting, colic, and may be headache with mild fever.
- Laboratory diagnosis: depends on culturing of food samples, vomitus and stool to detect the causative organism.
Steps of investigation of an outbreak
- confirmation of the existence of an outbreak
- By comparing the frequency of the disease with the frequency during the same period of the previous year.
- An epidemic exists when the number of cases is more than the expected number in relation to past experience .e.g. cholera – food poisoning - viral hepatitis – gastro-enteritis –polio.
An epidemic exists when …..
- the number of cases is more than the expected number in relation to past experience .e.g. cholera – food poisoning - viral hepatitis – gastro-enteritis –polio.
Steps of investigation of an outbreak
- cases finding and their characteristics
A map of locality with a rapid house to hous search.
Number every house in the locality.
Enumerate the population by age & sex.
Epidemiological surveillance & Epidemiological case sheet & its contents
Epidemiological surveillance
- The period for case finding is twice the incubation
period of disease from the occurrence of the last case.
Epidemiological case sheet & its contents
age - sex -occupation - onset of disease - diagnosis - personal contacts at home, workplace, school & other places especially events as parties & history of immunization.
Steps of investigation of an outbreak
- Study of Ecological Factors (Environmental Factors)
Change in temperature or humidity.
Pollution of water supply
Population dynamics of insects & animal reservoir.
Fairs & festivals.
Movement of the human population.
Steps of investigation of an outbreak
- Investigations of population risk
(Who share the same environment)
Steps of investigation of an outbreak
- Data analysis
- A complete list of the cases by chronological order to show: commencement & peak of the epidemic.
- Find out the 1st or index case: to trace source of infection.
- Epidemic curves are plotted
- Specific incidence rates & case fatality rates are worked out for different subgroups of population such as, age, sex, & occupation.
- The data are also related to environmental factors.
A complete list of the cases by chronological order to show: ….
commencement & peak of the epidemic.
Find out the 1st or index case to …..
trace source of infection.
- Epidemic curves are plotted
- Specific incidence rates & case fatality rates are worked out for different subgroups of population such as, age, sex, & occupation.
- The data are also related to environmental factors.
…
Steps of investigation of an outbreak
- Formation of hypothesis
Explaining the epidemic in terms of its origin, causative factors & mode of spread.
Steps of investigation of an outbreak
- Recommendation for prevention and control
….
Def of Epidemic curve
A histogram that shows the course of a disease outbreak by plotting the number of cases by the onset of illness.
Importance of Epidemic curve
- Epidemic Curve provides info on …..
❶ Probable time of exposure of cases to a source of infection.
❷ Probable incubation period.
❸ Whether the outbreak was due to a common point source (as contaminated food), a propagated source (as person-to-person contact) or both
❹ Whether the outbreak was time limited or ongoing.
Classification of epidemics & epidemic curve
Def of common source epidemic
- It is the one in which people are exposed intermittently or continuously to a common harmful
source. - The period of exposure may be brief or long.
Period of exposure in common source epidemic
The period of exposure may be brief or long.
Def of Propagated epidemic
- The propagated epidemics last longer than common source epidemics due to spread from person to person
Types of Common source epidemic
❶ An intermittent Exposure Epidemic Curve.
❷ Continuous Exposure Epidemic Curve.
❸ A point Source Exposure Epidemic Curve.
epidemic curve in intermittent exposure
- An epidemic curve with irregular peaks reflecting the timing & extent of the exposure
Examples of Epidemic curve of intermittent exposure
water borne outbreak due to intermittent contamination of community water supply
Epidemic curve of Continous exposure
Cases rise gradually & possibly plateau, rather than peak.
Example of Epidemic curve of Continous exposure
a waterborne outbreak due to continuous contamination of community water supply.
Epidemic curve of Point source exposure
An epidemic curve with a sharp upward slope & a gradual downward slope.
Example of Epidemic curve of Point source exposure
- It is common source outbreak in which exposure period is relatively brief & all cases occur within one incubation period.
Characters of Propagated epidemics
- It lasts longer than the common source epidemic
- may lead to multiple waves of infection if secondary and tertiary cases occur.
- The classic propagated epidemic curve has a series of progressively taller peaks, each with an incubation period apart.
The pattern of a common-source outbreak followed by secondary person-to-person spread is not uncommon
- These are called …. epidemics.
mixed
Example of Mixed Epidemics
