S3: Outbreak Investigation

Question 1

Def of Endemic

Answer 1

• Constant presence of a disease all over the year in certain area

Question 2

Def of Epidemic

Answer 2

• Sudden appearance of a disease in certain area or in a specific time in excess of normal expectations based on past experience

Question 3

Def of Outbreak

Answer 3

Localized epidemic

Question 4

def of Pandemic

Answer 4

• Epidemic of a disease spread from one country to another in short time

OR

• a disease occurs at same time in different countries

Question 5

Def of Sporadic

Answer 5

refers to a disease that occurs infrequently and irregularly.

Question 6

Def of Outbreak in Details

Answer 6

Localized epidemic
 In a given area
 Over a particular period of time.
 Among specific group of people

Question 7

Objectives of investigation of an outbreak

Answer 7

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

Question 8

Steps of investigation of an outbreak

Answer 8

Summary

Question 9

Steps of investigation of an outbreak

• Verification of diagnosis by clinical and labor Methods

Answer 9

**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.

Question 10

Steps of investigation of an outbreak

• confirmation of the existence of an outbreak

Answer 10

• 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.

Question 11

An epidemic exists when …..

Answer 11

• 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.

Question 12

Steps of investigation of an outbreak

• cases finding and their characteristics

Answer 12

 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

Question 13

Epidemiological surveillance

Answer 13

• The period for case finding is twice the incubation
  period of disease from the occurrence of the last case.

Question 14

Epidemiological case sheet & its contents

Answer 14

age - sex -occupation - onset of disease - diagnosis - personal contacts at home, workplace, school & other places especially events as parties & history of immunization.

Question 15

Steps of investigation of an outbreak

• Study of Ecological Factors (Environmental Factors)

Answer 15

 Change in temperature or humidity.
 Pollution of water supply
 Population dynamics of insects & animal reservoir.
 Fairs & festivals.
 Movement of the human population.

Question 16

Steps of investigation of an outbreak

• Investigations of population risk

Answer 16

(Who share the same environment)

Question 17

Steps of investigation of an outbreak

• Data analysis

Answer 17

• 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.

Question 18

A complete list of the cases by chronological order to show: ….

Answer 18

commencement & peak of the epidemic.

Question 19

Find out the 1st or index case to …..

Answer 19

trace source of infection.

Question 20

• 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.

Answer 20

…

Question 21

Steps of investigation of an outbreak

• Formation of hypothesis

Answer 21

Explaining the epidemic in terms of its origin, causative factors & mode of spread.

Question 21

Steps of investigation of an outbreak

• Recommendation for prevention and control

Answer 21

….

Question 22

Def of Epidemic curve

Answer 22

A histogram that shows the course of a disease outbreak by plotting the number of cases by the onset of illness.

Question 23

Importance of Epidemic curve

• Epidemic Curve provides info on …..

Answer 23

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.

Question 24

Classification of epidemics & epidemic curve

Answer 24

Question 25

Def of **common source epidemic**

Answer 25

- 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.

Question 26

Period of exposure in common source epidemic

Answer 26

The period of exposure may be brief or long.

Question 27

Def of **Propagated epidemic**

Answer 27

- The propagated epidemics last longer than common source epidemics due to spread from person to person

Question 28

Types of **Common source epidemic**

Answer 28

❶ An intermittent Exposure Epidemic Curve. ❷ Continuous Exposure Epidemic Curve. ❸ A point Source Exposure Epidemic Curve.

Question 29

epidemic curve in intermittent exposure

Answer 29

- An epidemic curve with irregular peaks reflecting the timing & extent of the exposure

Question 30

Examples of Epidemic curve of intermittent exposure

Answer 30

water borne outbreak due to intermittent contamination of community water supply

Question 31

Epidemic curve of Continous exposure

Answer 31

Cases rise gradually & possibly plateau, rather than peak.

Question 32

Example of Epidemic curve of Continous exposure

Answer 32

a waterborne outbreak due to continuous contamination of community water supply.

Question 33

Epidemic curve of Point source exposure

Answer 33

An epidemic curve with a sharp upward slope & a gradual downward slope.

Question 34

Example of Epidemic curve of Point source exposure

Answer 34

- It is common source outbreak in which exposure period is relatively brief & all cases occur within one incubation period.

Question 35

Characters of **Propagated epidemics**

Answer 35

- 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.

Question 36

The pattern of a common-source outbreak followed by secondary person-to-person spread is not uncommon - These are called .... epidemics.

Answer 36

mixed

Question 37

Example of Mixed Epidemics

Answer 37