Introduction to Surveillance

Session 4, Part 1

Learning ObjectivesSession 4, Part 1

• Explain the surveillance “feedback loop” of data and information flow through local, state, and federal channels

• Describe characteristics of three different methods of surveillance: active, passive, and syndromic

• List 5 applications of public health surveillance

OverviewSession 4, Part 1

• How surveillance works• Passive, active, and syndromic

surveillance• Applications of surveillance data• Surveillance limitations and challenges

How Surveillance Works

What is Surveillance?

The ongoing systematic collection, analysis, and interpretation of health data, essential

to the planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination to

those who need to know.

- Centers for Disease Control and Prevention (CDC)

• Physicians

• Laboratories

• STD clinics

• Community health clinics

• Emergency departments (EDs)

County and state health departments, CDC analyze data using statistical methods

Standardized data collection

Surveillance Flow

• Physicians

• Laboratories

• STD clinics

• Community health clinics

• EDs

County and state health departments, CDC analyze data using statistical methods

• Public health officials

• Health directors

• Health policy officials

Standardized data collection

Dissemination to those who need to know

Dissemination to those who need to know

Surveillance Flow

• Physicians

• Laboratories

• STD clinics

• Community health clinics

• EDs

County and state health departments, CDC analyze data using statistical methods

• Public health officials

• Health directors

• Health policy officials

Standardized data collection

Dissemination to those who need to know

Dissemination to those who need to know

Change in public health practice (vaccination, reduction of risk factors, medical intervention, etc.)

Public health planning and intervention

Surveillance Flow

• Physicians

• Laboratories

• STD clinics

• Community health clinics

• EDs

County and state health departments, CDC analyze data using statistical methods

• Public health officials

• Health directors

• Health policy officials

Standardized data collection

Dissemination to those who need to know

Dissemination to those who need to know

Change in public health practice (vaccination, reduction of risk factors, medical intervention, etc.)

Public health planning and intervention

Public health evaluation

Surveillance Flow

National Notifiable Diseases Surveillance System (NNDSS)

• National list– ~60 nationally infectious diseases – ~6 non-infectious diseases / conditions– Produced by CSTE each year

• State list– Each state modifies as needed– State law mandates reporting requirements

Sources of Surveillance Data

• Mortality reporting – Legally required as part of vital statistics

programs in most countries• Morbidity reporting

– Notifiable disease reporting (legally required) or specially created systems

Sources of Surveillance Data

• Surveys, e.g. BRFSS

• Epidemic reporting / cluster investigation

• Laboratory investigations and reporting

• Individual investigations

Management of Surveillance Data

• Timeliness• Completeness• Accuracy

Analysis of Surveillance Data • Trends• Clusters• Patterns

Methods of Surveillance

Passive

Active

Syndromic

Passive Surveillance

Laboratories, physicians, or other health care providers regularly report cases of disease to the local or state health department based on a standard case definition of that particular disease.

Communicable Disease Reporting:Passive Surveillance

Hospital PhysicianLab

Local Health

DepartmentState

CDC

Public

Excerpt: 2011 Recommended Reportable Diseases

• Anthrax• Arboviral neuroinvasive

and non-neuroinvasive diseases– California serogroup virus

disease– Eastern equine encephalitis

virus disease– Powassan virus disease– St. Louis encephalitis virus

disease– West Nile virus disease– Western equine encephalitis

virus disease

• Babesiosis

• Botulism– Botulism, foodborne– Botulism, infant– Botulism, other (wound &

unspecified)

• Brucellosis• Chancroid• Chlamydia trachomatis

 infection• Cholera

Specific reportable diseases and conditions are mandated by state law, and can differ for every state.

Active Surveillance

Local or state health departments initiate the collection of specific cases of disease from laboratories, physicians, or other health care providers.

Communicable Disease Reporting:Active Surveillance

Hospital PhysicianLab

Local Heath Department

State

CDC

• Outbreak investigations

• Other times when complete case ascertainment is desired – Research study– Incomplete information

reported

Active Surveillance Applications

Advantages and Limitations

Passive Surveillance• Advantages

– Inexpensive– Low data collection

burden for health department

• Limitations– Under-reporting– Missing information – Can be slow

Active Surveillance• Advantages

– Complete data– Flexible

• Limitations– Costly

Syndromic Surveillance

The ongoing, systematic collection, analysis, interpretation, and application of real-time indicators for disease that allow for detection before public health authorities would otherwise identify them.

What are “Indicators of Disease?”

• Clinical signs that we can categorize into syndromes

• Not a specific diagnosis

Example:

Cough + Sore throat + Fatigue + Fever = Influenza-like illness

Syndromic Surveillance Example

Source: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=18905

Daily temperatures and GP visits for heat syndrome, Bordeaux, 1 June – 31 Aug, 2006

Common SyndromesUnder Surveillance

• Gastroenteritis• Influenza-like illness (ILI)• Meningitis / Encephalitis• Rash / Fever sydromes• Botulinic syndrome• Hemorrhagic syndromes

Why Do Syndromic Surveillance?

• Early detection– Ideally automated

• Outbreak characterization– Magnitude, rate of spread,

effectiveness of control measures

• Detection of unexplained deaths

Limitations of Syndromic Surveillance (1)

• Limited by available data– False alarms– Inconsistent reporting sources– IT failure

Limitations of Syndromic Surveillance (2)

• Inadequate sensitivity: failure to detect outbreaks or emergencies– Outbreak is too small– Population disperses after exposure, cluster

not evident

Limitations of Syndromic Surveillance (3)

• Costly– Infrastructure and staff– Complicated data use agreements

Surveillance Applications

Applications• Establish public health priorities

• Aid in determining resource allocation

• Assess public health programs– Facilitate research

• Determine baseline level of disease

• Detect epidemics– Estimate magnitude of the problem– Determine geographical distribution

Establish Public Health Priorities

• Frequency – Incidence, prevalence,

mortality, years of life lost

• Severity – Case fatality rate,

hospitalization, disability

• Cost – Direct, indirect

Resource Allocation

TUBERCULOSIS: Reported cases per 100,000 population, United States, 2010

Source: National TB Surveillance SystemMMWR March 25, 2011 / 60(11);333-337

1998-1999

1999-2000

2000-2001

2001-2002

2002-2003

2003-2004

2004-2005

2005-2006

2006-2007

2007-2008

2008-2009

2009-2010*

0

200

400

600

800

1000

1200

Year

Nu

mb

er

of

La

bo

rato

ry C

on

firm

ed

C

as

es

Assess Public Health ProgramsLaboratory Confirmed Cases of Meningitis C,

England and Wales, 1998 - 2010

Source: Health Protection Agency, Infectious Diseases, Meningitis, Epidemiologic Datahttp://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1234859709051?p=1201094595391

Determine Baseline RatesTB Case Rates in U.S.-born vs. Foreign-born

Persons United States, 1993–2009*

Cas

es p

er 1

00,0

00

*Updated as of July 1, 2010.

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

0

10

20

30

40

U.S.-born Foreign-born U.S. Overall

Early Detection of Epidemics0

5010

015

020

0N

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Number of flu patients by monthBoston, MA

Surveillance Limitations and Challenges

Surveillance Limitations (1)

• Uneven application of information technology – Paper-based versus electronic

• Timeliness– Reporting time requirement– Reporting burden

Surveillance Limitations (2)

• Completeness– Unreported cases– Incomplete reports– Consistency of reporting

CDC

Varied communications methods and security - specific to each system- including paper forms, diskettes, e-mail, direct modem lines, etc.

Current Situation

MMWR Weekly TablesMMWR Annual Summaries

Program Specific Reports and Summaries

State Health Dept

TIMSSTD*MIS

HARS

HARS STD*MIS TIMS NETSS EIP Systems

NETSS

STD*MIS (Optional at the Clinic)

TIMS (Optionalat the Clinic)

PHLISEIP Systems*

PHLIS

HARS STD*MIS

TIMS NNDSS EIP Systems

PHLIS

* EIP Systems (ABC, UD, Foodnet)

Data SourcesPhysicians

Varied communications methods and security - specific to each system - including diskettes, e-mail, direct modem lines, etc.

Chart Review

Lab Reports

Reporting by Paper Form, Telephone & Fax

Statistical Surveys for Chronic Diseases, Injuries and Other Public Health Problems

City/County Health Department

Limitations: Multiple Categorical Systems

National Electronic Disease Surveillance System (NEDSS)

• Not a traditional surveillance system

• Electronically integrates existing surveillance systems for easy data collection, storage and access

• Includes security measures to ensure confidentiality

• Allows data queries

Surveillance Challenges

• Assessing quality of the data

• Using case definitions

• Translating data into information

Quality of the Data

• Completeness of case ascertainment

• Assessment of completeness, accuracy, and timeliness of reports

‘Tip of the iceberg’

Diagnosis is reported

Diagnosis is made

Patients visit healthcare provider

Ill Patients

Surveillance Challenges by Definition

• Clinical vs. surveillance case definitions

• Cases ‘worked’ vs. cases ‘counted’

• Place of exposure, residence, or diagnosis

• Re-infection or duplicate report

• Frequencies by date of onset, date of diagnosis, or date of report

Translating Data into Information

• Provides the basis for public health action

• Requires sound analysis and interpretation

• Extracts meaningful, actionable findings

• Requires clear presentation of complex issues

Summary• Public health surveillance is the ongoing

collection, analysis, interpretation of health data and dissemination of information

• Surveillance data are used for planning, implementation, and evaluation of public health practice

• Surveillance data collection can be passive, active, or syndromic; each type presents unique advantages and limitations

References and Resources• Bonetti M, et al. Syndromic Surveillance. Harvard Center for Public Health

Preparedness; August 2003. • Public Health Surveillance Program Office [Web page]. Centers for Disease

Control and Prevention. Available at: http://www.cdc.gov/osels/ph_surveillance/. Accessed March 1, 2012.

• State Electronic Disease Surveillance Systems --- United States, 2007 and 2010. MMWR Morb Mortal Wkly Rep. 2011;60(41):1421-1423. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6041a3.htm?s_cid=mm6041a3_w. Accessed March 1, 2012.

• Nationally Notifiable Conditions [Web page]. Division of Notifiable Diseases and Healthcare Information, Centers for Disease Control and Prevention. Available at: http://www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm. Accessed March 1, 2012.

References and Resources • Notifiable Diseases/Deaths in Selected Cities Weekly Information. MMWR

Morb Mortal Wkly Rep. 2004;53(21):460-468. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5321md.htm. Accessed March 1, 2012.

• Flamand C, Larrieu S, Couvy F, Jouves B, Josseran L, Filleul L. Validation of a Syndromic Surveillance System using General Practioner House Calls Network, Bordeaux, France. Eurosurveillance. 2008;13(25). Available at: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=18905. Accessed March 1, 2012.