INVESTIGATION OF COMMUNICABLE DISEASE

EPIDEMICS OR OUTBREAKS

Dr. Malimu, Public health,Msc. Epidemiology,PhD Cand.)

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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.

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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

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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.

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What is an epidemic/outbreak? Occurrence of more cases than

expected at that place and at that time.

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Incidence of Kaposi's Sarcoma (KS), Pneumocystis carinii Pneumonia (PCP), and Other Opportunistic Infections in the U.S., 1979-1981

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ND

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ND

JF

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0

5

10

15

20Cases, by month of onset

KSPCP(KS+PCP) or Other

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Reasons for investigating Reasons 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).

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Steps for investigating a Steps 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.

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Steps for investigating a Steps for investigating a communicable disease outbreak 2communicable disease outbreak 2

8. Set up immediate control measures.9. Address the resource gaps10. Report writing. 11. Dissemination of findings.12. Intensify surveillance.

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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.

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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.

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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.

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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.

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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).

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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.

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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?

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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VHF Deaths, Bandudu Province, ZaireMarch - 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.

of d

eath

s*

Surgery andHospital Outbreak

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Incidence of Kaposi's Sarcoma (KS), Pneumocystis carinii Pneumonia (PCP), and Other Opportunistic Infections in the U.S., 1979-1981

JF

MA

MJ

JA

SO

ND

JF

MA

MJ

JA

SO

ND

JF

MA

MJ

JA

SO

0

5

10

15

20Cases, by month of onset

KSPCP(KS+PCP) or Other

27

VHF Deaths, Bandudu Province, DRCMarch - 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.

of d

eath

s*

Surgery andHospital Outbreak

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RVF outbreak in TZ -2007