Public Health Surveillance

Ashry Gad MohamedMB.ChB, MPH, DrPH

Prof. of Epidemiology

Contents• Definition• Importance• Elements• Objectives• Types• Procedures of data collection• Analysis• Action • Reports

Public Health Surveillance

“Ongoing systematic collection, analysis, and interpretation of outcome-specific data for use in the planning, implementation, and evaluation of public health practice.”

CDC

Surveillance System Data Collection

Analysis Dissemination

Surveillance for communicable diseases remains important…

• The world population is highly mobile

• International travel and troop movements increase the risk of communicable disease transmission

• Migration for war and famine, and voluntary immigration increase communicable disease risk

• Naturally occurring disease is not our only threat

Elements of surveillance

• Cases and deaths due to a given disease.• Laboratory results.• Prevention and control measures.• Environment.• Vector.• Reservoir.• Population

Conceptual TaxonomyPublic Health Surveillance

Disease

Traditional ‘Syndromic’Drug Vaccine

Birth defect Injuries

Other

Etc.

Infectious Disease

Medical Utilizationand Adverse Events

OtherProducts/Services

Objectives of surveillance

1. Identify diseases of public health importance.

2. Identify quickly any outbreak, epidemic or unusual event.

3. Identify risk factors.4. Identify high risk population.5. Monitor disease trend.6. Access current disease control activities.

What data do we collect?

1. Should be preceeded by careful selection of diseases or conditions.

2. Should be indicated.3. Specify the indicator for each item

wanted to be monitored.4. It may requires In-Depth interview, if

decision to investigate causes is taken.

Types of SurveillancePassive

– Inexpensive, provider-initiated– Good for monitoring large numbers of typical

health events– Under-reporting is a problem

Active – More expensive, Health Department-initiated– Good for detecting small numbers of unusual

health events– Enhanced– Rapid reporting and communication between

surveillance agencies and stakeholders– Best for detecting outbreaks and potentially

severe public health problems

Data collection1. Routine reporting system Hospitals, health centers, health

facilities, CHW.Advantages:Inexpensive efficient.Standardized.,Disadvantages:IncompleteBusy doctors & nurses

New and complex disease entities must also be monitored…

• New syndromes may emerge that present in an atypical manner

• Syndromic surveillance uses health-related data that precede diagnosis and signal a sufficient probability of a case or an outbreak to warrant further public health response

• Day 1- feels fine• Day 2- headaches, fever - buys Tylenol• Day 3- develops cough - calls nurse hotline• Day 4- Sees private doctor – dx with “flu”• Day 5- Worsens - calls ambulance seen in ED• Day 6- Admitted - “pneumonia”• Day 7- Critically ill - ICU• Day 8- Expires - “respiratory failure”• Case enters surveillance system through an

EDC

Example of Passive Surveillance

• Day 1- feels fine• Day 2- headaches, fever - buys Tylenol• Day 3- develops cough - calls nurse hotline• Day 4- Sees private doctor - dx “flu”• Day 5- Worsens - calls ambulance - seen in ED• Day 6- Admitted - “pneumonia”• Day 7- Critically ill - ICU• Day 8- Expires - “respiratory failure”• Case is under immediate investigation by the

LHD because of the pre-diagnostic information gathered

Pharmaceutical Sales

Nurse’s Hotline

Managed Care Org

Ambulance Dispatch (EMS)

ED Logs

Absenteeism records

Example of Syndromic Surveillance

2-Sentnel reporting systemSelected health units

Advantages:More consistent pictures.Motivated.

Disadvantages:Not representativeChanged with surved population

3-Surveys and special studiesBroad estimate.Measure reliability.Relieve health care workers.

Disadvantages:Large sample size.Expensive

4-Case and outbreak investigationsOn occasion.Used as a next step

Data collection procedures• Operational definition• InstrumentsRegistersQuestionnairesCase investigation form• Pre-test the instrument

Data collection

• Training• Supervision• Quality control• Reporting

Analyze the data• Summary tables.• Disease charts.• Maps.• Rates & ratios• More analysis for pattern and

causes

Investigate causation• Case and outbreak investigations.• Verbal autopsy.

Develop an action plan

• What?• Who?• When?• Where?• How?• How?• Outline resources.

Prepare and present reports

• Review objectives.• Review tables, graphs & maps.• Add short narrative to explain findings.• Describe action plan.

• Disseminate the report