This document outlines the steps for investigating communicable disease outbreaks. It begins with an introduction that defines communicable diseases and provides examples. There are then 12 steps described for investigating an outbreak, including verifying diagnoses, establishing the existence of an epidemic, identifying and counting cases, analyzing data, formulating hypotheses, assessing local response capacity, setting control measures, addressing resource gaps, reporting, disseminating findings, and intensifying surveillance. The roles of the Ministry of Health, District Health Team, and health units in outbreak investigations and control are also outlined.

1. INVESTIGATION OF
COMMUNICABLE DISEASE
EPIDEMICS OR
OUTBREAKS
Dr. Malimu, Public health,Msc.
Epidemiology,PhD Cand.)

2. 2
Outline of the presentation
 Introduction.
 Reason for investigating communicable
disease outbreaks.
 Steps of a communicable disease outbreak
investigation.
 Role of the Ministry of Health in the
investigation of communicable disease
outbreaks.
 Role of the District Health Team in the
investigation of communicable disease
outbreaks.

3. 3
IntroductionIntroduction
 Definition of a communicable disease:
- Disease that easily passes from one person to
another through direct (person-to-person)
transmission or indirect (vehicles, fomites,
vectors) transmission.
 Factors that influence development of the
disease:
- Epidemiological triangle:
Host
Agent Environment

4. 4
IntroductionIntroduction
 Examples:
1. Epidemic-prone:
Meningococcal meningitis, cholera,
dysentery, plague, measles, viral
haemorrhagic fever, etc.
2. Diseases targeted for eradication/
elimination:
Polio (/AFP), Measles.
3. Diseases of public health importance:
Malaria, Sleeping sickness, AIDS, etc.

5. 5
What is an epidemic/outbreak?
 Occurrence of more cases than
expected at that place and at that time.

6. 6
Incidence of Kaposi's Sarcoma (KS),
Pneumocystis carinii Pneumonia (PCP), and
Other Opportunistic Infections in the U.S., 1979-1981
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
A
S
O
0
5
10
15
20
Cases, by month of onset
KS
PCP
(KS+PCP) or Other

7. 7
Reasons for investigatingReasons for investigating
communicable disease outbreakscommunicable disease outbreaks
 Know what you are dealing with.
 Assess magnitude (severity of illness, potential for further
spread).
 Alert by surveillance system, clinicians, laboratory,
community).
 Guidance on control measures needed (to prevent
further spread and minimize deaths).
 Mandate of MOH (program considerations)
 Political pressure/ legal obligation, public concern.
 Train field staff, epidemiologists.
 Research opportunity (unknown illness, known illness but
need to understand better).

8. 8
Steps for investigating aSteps for investigating a
communicable disease outbreak 1communicable disease outbreak 1
1. Prepare for field work.
2. Verify the diagnosis.
3. Establish existence of an epidemic.
4. Identify and count cases.
5. Data analysis.
6. Formulate and test hypothesis.
7. Assess the local response capacity.

9. 9
Steps for investigating aSteps for investigating a
communicable disease outbreak 2communicable disease outbreak 2
8. Set up immediate control measures.
9. Address the resource gaps
10. Report writing.
11. Dissemination of findings.
12. Intensify surveillance.

10. 10
1. Prepare for field work
 Assemble a team (Rapid Response team).
 Assemble relevant supplies and equipment
(transport media, specimen bottles, IEC,
treatment guidelines & medical supplies,
transport, communication means,
investigation and surveillance forms, funds,
fuel, etc).
 Alert district authorities.

11. 11
2. Verify the diagnosis
 Review clinical findings.
 Visit patients yourself (interview and
examine for symptoms and signs).
 Laboratory diagnosis.
 Choose a working case definition: who
is a case and who is not (by person,
place, time). Should be highly
sensitive.
 Establish index case.

12. 12
3. Establish existence of an
epidemic
 Compare observed incidence with
expected:
- No seasonality: compare with incidence from
previous weeks/ months,
- Seasonality: compare incidence from similar
periods of earlier years.
 Use action threshold.

13. 13
4. Identify and count cases
 Using the working case definition.
 Collect information on cases (deaths) and
line-list, e.g. identifying information: name,
address.
- Demographic: age, sex, tribe.
- Clinical: symptoms and signs, date of onset,
lab results, treatment, outcome of treatment.
- Exposure and risk factor information.

14. 14
5. Data analysis
 To describe the outbreak by person (tables,
bar charts, pie charts), place (spot maps)
and time (histograms, graphs).
 Person: who is the population at risk (age,
sex, race, occupation, medical status, etc).
 Exposure: occupation,. Environment, cultural
practices, socio-economic factors, etc.
 Get the population size at risk. Calculate
Attack Rate, Case Fatality Rate (assess
quality of case management).

15. 15
6. Formulate and test hypothesis
 Hypothesis should address:
- Source of the agent.
- Mode of transmission.
- Exposures (risk factors).
 Where resources are available and cause
not obvious, compare cases with controls in
respect to exposure. Do OR, chi test, look up
p-value.
 If sure of the cause, then may need only to
study the cases.

16. 16
7. Assess the local response capacity
 What number and type of staff is available
locally?
 Which drugs/ medical supplies/ guidelines
are available to treat the cases?
 What has been done in terms of epidemic
response?
 What steps have been taken to interrupt
transmission?
 Has any health education been conducted?

17. 17
8.Set up immediate control measures
 Be guided by the Epidemiological triangle:
- Agent.
- Host.
- Reservoir.
 Deal with the reservoir (if any).
 Interrupt transmission.
 Reduce susceptibility of the host (vaccination,
chemo-prophylaxis, improve nutrition, etc).
Treat cases.

18. 18
9.Address the resource gaps
 Done as need may arise:
 Laboratory support.
 Environmental support.
 Public information.
 Specific disease control needs in terms of:
- Personnel,
- Drugs, vaccines and equipment,
- Transport, communication and logistics.

19. 19
10. Report writing
 Describe the situation using the answers and
comments to the steps outlined above.
 Describe the need for outside assistance
based on the gap in resources.
 Make conclusions on the outbreak you are
dealing with.
 Give recommendations on priority activities
(short term, long term) based on findings and
conclusions.

20. 20
11. Dissemination of findings
 Convey the report to Ministry of Health
(relevant division/ program, senior/ top
management)
 If epidemic has been confirmed,
convey report to WHO through top
management.
 Disseminate report to the DHT.

21. 21
12. Intensify surveillance
 Maintain contact with the district for
daily updates (cases, deaths, number
admitted, number discharged, areas
affected, etc) until end of the epidemic.

22. 22
Role of the Ministry of Health in the
investigation and control of communicable
disease outbreaks
Overall coordination, technical support,
development and provision of guidelines,
policy in the following areas:
 Coordination: National Task Force.
 Case management (Procurement and provision of
emergency supplies).
 Surveillance (ensure daily updates from affected districts,
report to partners and other stakeholders at national level,
alert neighboring districts).
 Public information.
 Environmental sanitation.
 Logistics management.
 Investigation:National rapid response team.

23. 23
Role of the District Health Team in the
investigation of communicable disease
outbreaks
District level coordination, dissemination of
guidelines, implementation of control
measures:
 Coordination:District Task Force
 Case management (transport emergency supplies to
affected area and serving health units, set up treatment
sites).
 Surveillance (retrieve data from health units and affected
communities, report to MOH and use the information for
control).
 Public information in the communities affected.
 Environmental sanitation and preventive measures:
address risk factors including mass immunization.
 Logistics management/monitoring.
 Investigation:District rapid response team.

24. 24
Role of the health units in the
investigation of communicable disease
outbreaks
 Surveillance:data collection, reporting.
 Case management: treatment of
cases.
 Follow-up of cases: home-visiting.
 Health education in the health unit.

25. 25
VHF Deaths, Bandudu Province, Zaire
March - April 1995
*Note: 7 deaths with unknown date of onset
3/27/953/29/953/31/954/2/954/4/954/6/954/8/954/10/954/12/954/14/954/16/954/18/954/20/954/22/954/24/954/26/954/28/954/30/955/2/955/4/955/6/955/8/955/10/955/12/955/14/955/16/955/18/955/20/95
Date of Death
0
5
10
15
20
No.ofdeaths*
Surgery and
Hospital Outbreak

26. 26
Incidence of Kaposi's Sarcoma (KS),
Pneumocystis carinii Pneumonia (PCP), and
Other Opportunistic Infections in the U.S., 1979-1981
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
A
S
O
0
5
10
15
20
Cases, by month of onset
KS
PCP
(KS+PCP) or Other

27. 27
VHF Deaths, Bandudu Province, DRC
March - April 1995
*Note: 7 deaths with unknown date of onset
3/27/953/29/953/31/954/2/954/4/954/6/954/8/954/10/954/12/954/14/954/16/954/18/954/20/954/22/954/24/954/26/954/28/954/30/955/2/955/4/955/6/955/8/955/10/955/12/955/14/955/16/955/18/955/20/95
Date of Death
0
5
10
15
20
No.ofdeaths*
Surgery and
Hospital Outbreak

28. 28
RVF outbreak in TZ -2007