Public health, outbreak and epidemic is used interchangeably .

1. OUTBREAK INVESTIGATION
(BMPB 211)

2. Outline
 What is an outbreak investigation
 Outbreak detection
 Outbreak investigation
 Outbreak control

3. What is an outbreak?
 A situation where there are more cases
recorded than what is normally expected
(baseline/threshold) in a given population
or geographical area.
 The terms epidemic and outbreak are
sometimes used interchangeably

4. Outbreak Detection
 There are several different ways of detecting
outbreaks.
 Existence of the outbreak may be known
through different surveillance methods:
Passive Surveillance
Active Surveillance
Sentinel Surveillance
Syndromic Surveillance
Events-based Surveillance

5. Outbreak Investigation
 Once a decision is made to investigate
an outbreak, a few systematic steps
need to be followed.
 The number of steps, order or content
can vary.
 Several steps can be done at the same
time

6. Steps in Outbreak Investigation
In essence, the investigation
consists of the following steps:
1. Confirm the outbreak
2. Describe the outbreak
3. Determine the case
4. Control the outbreak

7. Confirmation of the Outbreak
 First step in the investigation process
 Done to determine whether there are more
cases of an illness in the population than what
is expected. We need to know the baseline
level of the illness in that population at a given
time so that we can compare with the level of
illness we have seen to see if there is an
increase

8.  It is critical to know that the elevation
in the number of apparent cases
could be due to:
Sudden rise in the number of tests
conducted
Laboratory or diagnostic error
Sudden population increases
These need to be ruled out

9.  To work out the what is causing the outbreak
and decide the best control methods, it is
necessary to verify the diagnosis (Clinical &
Lab findings).
 At this stage there could already some
immediate actions that could have been taken
to control the outbreak, especially if the source
and mode of transmission are known.

10.  To proceed with the investigation, it
may be necessary to form an
investigation team.
 The size of the team will depend on
the nature of the outbreak being
investigated.

11. 2. DESCRIBE THE
OUTBREAK
 Describing the outbreak provides an
insight into
Who is affected
Where did the illnesses
occur/happen
What are the other characteristics
of the outbreak

12.  To describe the outbreak, investigators need to
determine:
1. Who should be considered a case-
Case determination
2. Determine whether all the cases have
been found-Contact tracing
3. Describe the cases

13. Who is a Case?
 There should be a case definition- Criteria to be
met for a person to be categorized as a case.
 Generally there are criteria for :
Person
Place
Time
Clinical criteria
Laboratory criteria

14. Cases Found-Contact Tracing
 Cases looked for in a systematic way and
information about cases is recorded.
 This is usually done using questionnaires.
 The cases are described in terms of Person,
Place & Time.

15. Time
 Investigators can look at how the
disease has developed over time.
 Typically displayed on the graph
as point-source outbreak or
propagated outbreak.

16. Place
 Provide information on the geographical
distribution of the spread of the
outbreak/disease and identify if there are
clusters.
 Modern mapping tools and GIS have become
handy and useful in tracking the outbreaks.

17. Person
 Who is affected in terms of:
 Age
 Sex
 Occupation
 Ethnicity
 Socioeconomic status, etc.
 The above factors can provide useful information
and insight on the disease.
 Can allow the investigators to figure out who is at
risk

18. 3. DETERMINE CAUSE OF THE
OUTBREAK
 From the information gathered so
far, investigators are likely to
figure out what could be the
cause of the outbreak.
 What is the likely cause-
Hypothesis

19.  If the pathogen for the disease is already
known, this could guide the investigators
to know the source of the outbreak, and its
mode of transmission.
 V. cholerae= Contaminated water
 Salmonella= Contaminated meat and
eggs

20. What is the likely
cause
Hypothesis
Test
Hypothesis
Analytical
studies
- Cohort
- Case-control
Analytical studies are used to determine the
possible factors that are likely to cause

21.  Environmental investigation can also
help in confirming the hypothesis.
 Laboratories= very useful (microbiological)
information to confirm the hypothesis

22. CONTROL
 This is the primary goal of investigating an
outbreak.
 Can happen at any stage of the outbreak
investigation and can be targeted at any step
of the transmission pathways between:
An agent
A host
Environment

23. Control Measures include:
 Behavioral interventions
 Using mosquito repellants
 Vaccinations
 Measles vaccinations
 Medication
 Ivermectin during scabies
 Environmental
 IRS and improvement of water quality during a cholera
outbreak
 Infection control measures
 Wearing PPEs, disinfection

24.  Health Education
 Targeted and appropriate education to increase
peoples knowledge, change behaviours and improve
health protective skills.
 Surveillance
 To monitor the outbreak and know if the preventive
methods put in place are working or not.

25. COMMUNICATION
 Important aspect of managing any outbreak
either big or small.
 Communication is all about making sure that
accurate and timely information gets to the
right people at the right time (Internal,
External and other organization)
 Communication helps organization to adopt
protective surveillance, reduces anxiety,
confusion, misinformation.