Surveillance Surveillance

Dr Amna Rehana SidiquiAssistant ProfessorDepartment of Family and Community Medicine

Learning Objectives:Learning Objectives:

After studying this lesson you will be able to:

• Define public health surveillance and its main components

• List the elements and uses of surveillance • Describe sources for data that can be used for

public health surveillance• Describe the flow of information for

reportable diseases

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.”

Definition by Centers for Disease Control (CDC) USA

Surveillance isSurveillance is

Information for Action

Reported TB Cases* United States, 1982–2006

10,000

12,000

14,000

16,000

18,000

20,000

22,000

24,000

26,000

28,000

1982 1986 1990 1994 1998 2002 2006

Year

No. of Cases

*Updated as of April 6, 2007.

The components of surveillance and resulting public health action

Elements of surveillance system

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

Fig. 2Cholera: Cholera: Reported cases & Case fatality Rates (CFR), by Continent

CFR= # of TB cases dying in that yr / # of TB cases identified in that yr

By

Conceptual Taxonomy

Public Health Surveillance

Disease

Traditional ‘Syndromic’Drug Vaccine

Birth defect Injuries

Other

Etc.

Infectious Disease

Medical Utilizationand Adverse Events

OtherProducts/Services

Purposes of Public Health Surveillance

•Assess public health status about a factor/s

•Setting public health priorities; e.g. polio first…

•Evaluate prevention and control programs

•Generating hypothesis & Stimulating research; e.g. relationship of TB and HIV

Uses of Public Health Surveillance

•Estimate magnitude of the problem•Guide immediate action for cases •Determine geographic distribution of illness•Portray the natural history of a disease•Detect epidemics/define a problem•Generate hypotheses, stimulate research•Monitor changes in infectious agents•Detect changes in health practices•Facilitate planning•Evaluate control measures•Policy Changes e.g. Measles vaccine booster

TB Case Rates,* United States, 2006

< 3.5 (year 2000 target)

3.6–4.6

> 4.6 (national average)

D.C.

*Cases per 100,000.

YearYear

Rep

ort

ed

Case

s (T

hou

sand

s)R

ep

ort

ed

Case

s (T

hou

san

ds) Vaccine

licensedVaccine licensed

00

5050

100

100

150

150

200

200

250

250

300

300

350350

400

400

450

450

500

500

1963

1963

1968

1968

1973

1973

1978

1978

1983

1983

1988

1988

1993

1993

1998

1998

MEASLES — by year, United States, 1983–1998MEASLES — by year, United States, 1983–1998

00

55

1010

1515

2020

2525

3030

YearYear

19831983 19881988 19931993 19981998Rep

ort

ed

Cases

Th

ou

san

ds)

Rep

ort

ed

Cases

Th

ou

san

ds)

Evaluate control measures of MEASLESEvaluate control measures of MEASLESUnited States, 1963-1998

Data Sources for Surveillance• Notifiable diseases (Reporting is mandatory,

legal, & reportable diseases vary by region)• Laboratory specimens (Salmonella—serotypes,

Blood Lead Measurements, HIV) • Vital records (Infant Mortality Surveillance,

Birth & Death Certificates)• Sentinel surveillance (selected sites ; work-

related Asthma, lead poisoning,…)• Registries (Cancer& congenital defects)• Surveys (Nutrition Examination Survey,….)• Other data sources (Vaccine Adverse Event

Reporting, drug reaction,…)

15

Types of SurveillancePassive surveillancePassive surveillancehealth-care providers send reports to a health

department on the basis of a known set of rules and regulations, is called passive surveillance.

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

events• Under-reporting is a problem

Active surveillanceActive surveillance▫active surveillance (health department- initiated)

health department approach health providers ; is usually limited to specific diseases over a limited period of time, such as after a community exposure or during an outbreak.

Attributes of a surveillance system --- Simplicity – time spent in maintaining

--- Flexibility – can adapt to changes--- Data quality - validity--- Acceptability – by stakeholders--- Sensitivity-can detect …--- Representativeness--- Timeliness – detected and reported --- Stability - continues without breaks

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

CHW.

Advantages:Inexpensive and 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

hospital reporting

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-Sentinel reporting system Selected health units; e.g. influenza in USA

to develop vaccine for that year after typing for circulating strain for that year

Advantages:More consistent pictures.Motivated.

Disadvantages:Not representativeChanges with served populatione.g. use of the same influenza vaccine in other

countries which was identified for USA population

3-Surveys and special studiese.g. The National Health and Nutrition Examination Survey

(NHANES) program of studies designed to assess the health and nutritional status of adults and children in the United States.

AdvantagesBroad estimate.Measure reliability.Relieve health care workers.

Disadvantages:Large sample size.Expensive

4-Case and outbreak investigationse.g. HIV cases when first identified

On occasion.On occasion.Used as a next step Used as a next step e.g. to plan interventionto plan intervention

Post outbreak surveillance Post outbreak surveillance (e.g. to confirm that (e.g. to confirm that outbreak is over)outbreak is over)

Early warning systems: Early warning systems: e.g. surveillance for risk e.g. surveillance for risk factors in malnourished children who may be vulnerable factors in malnourished children who may be vulnerable and will acquire diseases before it spreads in healthy and will acquire diseases before it spreads in healthy children children

Data collection procedures

•Operational definition•Instruments•Registers•Questionnaires•Case investigation form•Pre-test the instrument•Source; Laboratory; hospitals…

Data collection

•Training•Supervision•Quality control•Reporting; frequency for monitoring and interpretation

Analyze and interpret data

•Summary tables.•Disease charts.•Maps.•Rates & ratios•More analysis for pattern and causes

Steps in Surveillance data Analysis•Data quality

•Descriptive analysis▫Time

▫Place

▫Persons

•Generate hypothesis

•Test hypothesis

Data Quality Issues

•Missing values

•Attraction to round figures

•Data entry errors

•Bias related to lack of representativity▫Cases more severe

▫Urban > rural

▫Source not represented (private sector, GPs)

Data Quality

•completeness and validity of the data •percentage of "unknown" or "blank •Case definition •Training of team•Manuals•Active versus passive

Burden of diseases

•Reporting only confirmed cases may not reflect true status resulting in ineffective control as an iceberg situation may exist with clinical and subclinical cases

•Only severe cases are reported •Under reporting may lead to high case

fatality rates; resource utilization affected

Timeliness of disease notification1. Health event occurs2. Identified by health care system3. Reported to local health authority 4. Verification/investigation by PHS5. Health event reported to other systems6. Analyses of health data 7. Dissemination of surveillance finding8. Actions based on surveillance findings

Early warning system• Major threats to the population; 0-4 & 5 or

more years of age, have been identified.• Severe malnutrition, injuries, acute watery

diarrhoea, bloody diarrhoea, acute flaccid paralysis, acute respiratory infections, neonatal tetanus, malaria, suspected measles, suspected meningitis, acute jaundice syndrome and acute FUO

• A threshold for each is defined; unusual pattern or occurrence will triggers investigations and responses.

8/5/1430Dr. Salwa Tayel

33

Prepare and present reports

•Review objectives.

•Review tables, graphs & maps.

•Add short narrative to explain findings

COMPARING TO PREVIOUS REPORTS.

•Describe action plan.

•Disseminate the report

8/5/1430Dr. Salwa Tayel

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Surveillance system in Hospital•High risk of hospital acquired infections

(HAI) that leads to high mortality, longer length of stay, and huge costs of hospitalization

•First Surveillance and then research•How much mortality, cost, length of stay

could be averted by reducing HAI?

•How will you start?•Person, place and time ?

EXERCISE EXERCISE

Needs and Steps •Assess your resources•Step wise fashion or all at once?•Training of individuals •Pilot testing•Obtaining data, case definitions,

standards •Monitoring/continuous / frequency ? 3

months•Interpretation ; comparing rates by

quarters•Analyses ; developing research hypothesis•Dissemination ; publication

Descriptive epidemiology •What are the infection rates in ….•What is the mortality rate in ….•What is the usual length of stay …•What are the important organisms that

are reported from …..•Any previous data?•Any previous outbreak data?•Numerator?•Denominator?•Setting/s defined

Numerators

•Case definitions required •Sepsis, Pneumonias, UTI, SWI etc. •Who will diagnose ? (for stability of rates) •Standard definitions / CDC •Laboratory based surveillance •Active surveillance

Hospital Acquired Infections in High Risk Area (Mixed type ICU) April 1998 – March 2001

-5

0

5

10

15

20

25

30

Rat

e / 1

000

Dev

ice

DA

ys

BSI 26 27 23.5 22.72 24.76 15.9 21.27 13.88 18.7 18.6 8.6 5.1

Pneumonia 2.5 5.2 7.4 7.08 4.21 6.2 2.6 1.21 9.2 8.5 10.6 10.3

UTI 1.2 0 2.42 3.38 0 0 1.97 2 2.6 0.8 0 6.5

Apr-Jun'98

Jy-Sep'9

8

Oct-Dec'9

8

Jan-Mar'9

9

Apr-Jun'99

Jul-Sep'9

9

Oct-Dec'9

9

Jan-Mar'0

0

Apr-Jn00

Jy-Sep'0

0

Jan-M01

Reference 50th Percentile

BSI=Blood Stream Infections; UTI=Urinary Tract Infections

40

Summary Summary

•Surveillance for ………▫Case definition

▫Sources of data

▫Analysis

▫Interpretation

▫Dissemination - REPORTING

•Actions