Public Health Surveillance - Virginia Commonwealth University
Public Health Surveillance Diane Woolard, Ph.D., M.P.H. Division of Surveillance & Investigation Virginia Department of Health Objectives of Lecture Key concepts of surveillance Definition Uses Methods Public health surveillance systems Use and evaluation of surveillance systems What comes to mind when you hear surveillance? Law enforcement agencies
CIA Routine data collection Statistics Trends Definition of Surveillance The ongoing systematic collection, analysis, and interpretation of outcome-specific data for use in the planning, implementation, and evaluation of public health practice. Includes data collection, analysis, and dissemination to those responsible for prevention and control. What Surveillance Is Systematic, ongoing
Collection Analysis Interpretation Dissemination of health outcome data Health action investigation control prevention Surveillance History in U.S.
1741 Rhode Island law required tavern keepers to report contagious disease 1850 National mortality statistics first published by the federal government 1874 Massachusetts instituted weekly reporting of diseases by physicians 1878 Public Health Service (PHS)-type organization created to collect morbidity data for use in quarantine for cholera, smallpox, plague, yellow fever Surveillance History in U.S. 1901 All states required disease reporting 1925 All states began participating in national morbidity reporting 1935 First national health survey 1951 Council of State and Territorial
Epidemiologists (CSTE) authorized to determine diseases to be reported to PHS 1961 Morbidity and Mortality Weekly Report (MMWR) published Legal Authority for Surveillance Legal authority for mandatory public health surveillance resides with states Virginia Code 32.1-35 Board of Health (BOH) shall promulgate a list of diseases required to be reported 32.1-36 Physicians and laboratories shall report 32.1-37 Medical care facilities, schools and summer camps shall report Virginia Code, continued 32.1-38 Anyone making a report is immune
from liability 32.1-39 BOH shall provide for surveillance & investigation 32.1-40 Commissioner or designee can examine medical records 32.1-41 Anyone examining records must preserve anonymity of the patient and the practitioner Purpose of Surveillance To assess public health status, to define public health priorities, to evaluate programs, and to stimulate research. Tells us where the problems are, who is affected, and where the programmatic and prevention activities should be directed.
How can surveillance data be used? Estimates of a health problem Natural history of disease Detection of epidemics Distribution and spread of a health event Hypothesis testing Evaluating control and prevention measures Monitoring change Detecting changes in health practice
Facilitate planning Uses of Surveillance Data: Estimates of a Health Problem Quantitative estimates of the magnitude of a health problem Percent of Adults Who Are Obese (BMI 30), Virginia, 1995-2010 including sudden or long-term changes in trends, patterns Source: Virginia Behavioral Risk Factor Surveillance System (BRFSS)
Uses of Surveillance Data: Natural History of Disease Portrayal of the natural history of disease (clinical spectrum, epidemiology) Confirmed Lyme disease cases, by month of disease onset, United States, 2001-2010 Varicella Cases by Month Antelope Valley, CA, 19952004 600 500 Cases 400 300
200 100 0 1 7 1 7 1 7 1
7 1 7 1 7 1 7 1 7
1 7 1 7 Uses of Surveillance Data: Detection of Epidemics SALMONELLOSIS and SHIGELLOSIS Number* of reported cases, by year United States, 1979-2009 *In thousands Slide from CDC 2009 Annual Summary
Uses of Surveillance Data: Distribution & Spread of a Health Event West Nile Virus in the US, 2000-2003 2000 2002 2001 2003 Use of Surveillance Data: Hypothesis Testing Facilitation of epidemiologic and laboratory
research PERTUSSIS Number of reported cases*, by age group United States, 2009 Hypothesis testing *Of 16,858 cases, age was reported unknown for 187 (1.1%) cases. Slide from CDC 2009 Annual Summary Uses of Surveillance Data: Evaluating Control & Prevention Measures Effectiveness of vaccine introduction Uses of Surveillance Data:
Monitoring Changes Monitoring changes in infectious agents and host factors Uses of Surveillance Data: Detecting Changes in Health Practice Cesarean delivery rates: United States, 1991-2007 Uses of Surveillance Data: Facilitate Planning Identify target populations in need of health services Refugee populations Morbidity surveillance in emergency shelters
Identify health topics to be addressed by educational programs and media Outcomes Surveillance is outcome oriented. Can measure frequency of an illness or injury (e.g., number of cases, incidence, prevalence) Can measure severity of the condition (e.g., hospitalization rate, disability, case fatality) Can measure impact of the condition (e.g., cost) Orient data by person, place, and time Planning a Surveillance System Establish objectives Develop case definitions Determine data source or data collection
mechanism Field test methods Develop and test analytic approach Develop dissemination mechanism Assure use of analysis and interpretation What Should be Under Surveillance? Establish priorities based on: Frequency (incidence, prevalence, mortality) Severity (case-fatality, hospitalization rate, disability rate, years of potential life lost) Cost (direct and indirect) Preventability Communicability Public interest Will the data be useful for public health action?
Surveillance Methods: Case Definition Important to clearly define condition Ensures same criteria are used by all Makes the data more comparable Include person, place, time May define suspected and confirmed cases May include symptoms, lab values, time period, population as appropriate
Case Definition Examples Weak Definition - Measles Any person with a rash and fever, runny nose, or conjunctivitis Better Definition - Measles Any person with a fever >101 F, runny nose, conjunctivitis, red blotchy rash for at least 3 days, and laboratory confirmation of IgM antibodies Clinical, Probable, Confirmed Case Definitions Outbreak Case Definition Differs from routine surveillance Epidemiologically linked cases often included Case Definition Example: Giardiasis
Clinical description An illness caused by the protozoan Giardia lamblia (aka G. intestinalis or G. duodenalis) and characterized by gastrointestinal symptoms such as diarrhea, abdominal cramps, bloating, weight loss, or malabsorption. Laboratory criteria for diagnosis Laboratory-confirmed giardiasis shall be defined as the detection of Giardia organisms, antigen, or DNA in stool, intestinal fluid, tissue samples, biopsy specimens or other biological sample. Case classification Confirmed: a case that meets the clinical description and the criteria for laboratory confirmation as described above. When available, molecular characterization (e.g., assemblage designation) should be reported. Probable: a case that meets the clinical description and that is epidemiologically linked to a confirmed case. Surveillance Methods: Data Collection
Data collection Standardized instruments, field tested Passive surveillance* Providers are responsible for reporting Health dept. waits to receive reports Problem with underreporting Active surveillance* Providers contacted on regular basis to collect information More resource intensive Used for outbreaks or pilot studies * These are very key concepts Surveillance Methods: Data Analysis Ongoing review
Descriptive statistics, multivariate analyses Automated analyses Disease Number of cases Tuberculosis 20 Gonorrhea 320 Surveillance Methods: Interpretation and Dissemination
Presentation of data in the form of tables, graphs, maps, etc. Disseminate data via reports, presentations, internet, etc. Surveillance Methods: Evaluation Did the system generate needed answers to problems? Was the information timely? Was it useful for planners, researchers, etc? How was the information used? Was it worth the effort? What can be done to make it better? (More on evaluation later). Cycle of Surveillance
Data Collection Pertinent, regular, frequent, timely Consolidation and Interpretation Orderly, descriptive, evaluative, timely Dissemination Prompt, to all who need to know (data providers and action takers) Action to Control and Prevent Evaluation Data Sources
Vital Statistics Notifiable Diseases Registries Sentinel Surveillance Syndromic Surveillance Surveys Administrative Data Data Sources: Vital Statistics
Live Births Deaths Fetal Deaths Marriages Divorces Induced Terminations of Pregnancy Infant Mortality (link birth and death data) Virginia Birth Certificate Virginia Birth Certificate
Virginia Death Certificate M A S E L P Uses of Vital Statistics Data Monitoring long-term trends Identifying differences in health status within racial or other population subgroups Assessing differences by geographic area Monitoring deaths that are preventable
Generating hypotheses about causation Monitoring progress toward improved health of the population; health-planning Vital Records: Coding and Calculating ICD-9 historically, now ICD-10. Infant mortality - need number of live births for denominator in calculating rates. Other death rates - use total population in rate calculations. Crude and adjusted (standardized) rates used. Vital Statistics Data Quality of Vital Stats Depends on
Care taken by health care providers in ascertaining cause of death and other factors Accuracy of coding (difficult for injuries) Relevance of existing codes for the condition being recorded Accuracy of population estimates Problems - dont know onset, cant see effect of diseases that dont lead to death Data Sources: Notifiable Diseases States decide what is notifiable/reportable Based on disease occurrence, potential for outbreaks, public perception of risk, etc. CSTE recommendations Different processes for generating N.D. list
Weekly (or sometimes rapid) reporting to health departments by physicians, medical care facilities, laboratories. States report to CDC Virginia Reportable Disease List Over 70 reportable diseases/conditions Epi-1 Form Chain of Communication State
Physicians Labs Hospitals/Medical Care Facilities Other States Local H.D. Regional Epis Other Health Districts
Central Office CDC Electronic Surveillance National Electronic Disease Surveillance System (NEDSS) A set of criteria developed by CDC that all public health surveillance systems must meet Virginia adopted CDCs NEDSS Base System (VEDSS) Used to manage statewide reportable disease surveillance data Supported by CDC funds VEDSS
Shared secure web-based disease surveillance database for Virginia Eliminates delays in reporting Improves communication about cases Assists in earlier detection of events Provides more data in electronic form for analysis All Virginia health departments connected by the end of 2006 Includes electronic reporting from laboratories VEDSS Data Entry and Reports
STD Trends Over Time Elevated Blood Lead Levels in Children by Range of Elevation, Virginia, 2010 Geographic Distribution of Human Arbovirus Cases Recorded in Virginia since 1975 Human Arbovirus Infections Since 1975 WNV (67 cases)* SLE (8 cases)* LAC (29 cases)* EEE (5 cases)* *Number of cases through 9/08
WNV = West Nile virus SLE = St. Louis encephalitis virus LAC = La Crosse encephalitis virus EEE = Eastern equine encephalitis virus Primary pathogens causing central line-associated bloodstream infections, Virginia, 2010 Limitations of Disease Reporting Underreporting Reporting better for more serious diseases and those for which there is laboratory confirmation Need to seek medical consultation to be diagnosed and then reported
Lack of representativeness of reported cases Inconsistent case definitions Reasons for Not Reporting Assume someone else reported. Do not know reporting was required; dont have a copy of the reportable disease list. Do not know how to report; dont have form or telephone number. Concern about confidentiality and doctorpatient relationship. No incentive to report. Time-consuming. Unaware of value. How to Improve Reporting Contact physicians in the community. Tell them the health department is very
interested in morbidity reporting Maintain a reasonable list of reportable diseases. Maximize contact through presentations, mailings, newsletters, media, etc. Use the data. In Spite of Limitations... The best system we have for tracking communicable disease morbidity Information available quickly and from all jurisdictions Can detect outbreaks / changes in incidence Allows disease control measures to be implemented
Data Source: Registries Information from multiple sources is linked for each individual over time. Diverse sources of information. E.g., hospitals (sometimes >1), pathology, death certificates. Used for cancer, congenital anomalies, trauma, etc. Most are passive but resource intensive. More lag in data availability due to complexity of data collection process. Populations Covered by Registries Hospital-based Population-based Exposure registries
World Trade Center Health Registry Three Mile Island Example: Virginia Cancer Registry Methods prescribed by ACOS, NAACCR, Virginia regulations, CDC. Hospital registries are main source of data. Voluntary reporting, 1970-1989 Mandatory reporting, 1990-present Demographic, geographic, clinical data Annual merge with vital records for survival information. Registry Data Age-Adjusted Cancer Incidence Rates, All Sites, by Sex and Age, Virginia, 1999-2008
* Incidence rates reflect gender-specific cancers: Males (Prostate and Testis), and Females (Breast, Cervical, Ovarian, and Uterine). Rates are per 100,000 and age-adjusted to the 2000 US Std Population (19 age groups - Census P25-1130) standard. Source: Virginia Cancer Registry, May 2012 Data Source: Sentinel Systems To gather timely public health information in a relatively inexpensive manner. Cannot derive precise estimates of prevalence or incidence in the population. Sentinel health events Sentinel sites Sentinel providers Sentinel Health Events A condition whose occurrence serves as a
warning signal. Particularly useful for occupational exposures. Silicosis, occupational asthma, pesticide poisoning, lead poisoning, carpal tunnel syndrome. Cases trigger intervention activities. Sentinel Sites or Providers Surveillance at certain hospitals, clinics, or physician practices. Sentinel sites - monitor conditions in subgroups that may be more vulnerable E.g., drug clinic, STD clinic, MCH clinic Sentinel providers - monitor activity in ambulatory care settings.
For diseases that are not reportable For influenza Flu Surveillance Visits for influenza-like illness (ILI) Sentinel Providers / Lab Surveillance Outbreak Surveillance (and control) Pediatric Deaths report to health dept if flu-associated death and age < 18 Weekly Activity Level Influenza Incidence Surveillance Project
ILI Visits Reported from ED/Urgent Care Sentinel Providers/Lab Surveillance 55 sentinel provider sites from 31 health districts 29 physician offices 26 ED/urgent care facilities. Providers submit two specimens per month from patients meeting the ILI case definition to DCLS fever with sore throat and/or cough in the absence of another known cause Confirmatory lab results from other labs also used Identifies which particular flu viruses are circulating
Flu Outbreak Surveillance Outbreaks are reported by phone Most are from group residential settings VDH recommends control measures 5-6 specimens collected/outbreak for lab testing Monitor outbreak to its end Complete outbreak report form for documentation 66 Flu - Weekly Activity Level
None Sporadic Local Regional Widespread Based on ILI visits/region, lab findings, outbreaks Reported to CDC
Shown on weekly State Epidemiologist map 67 *Influenza Incidence Surveillance Project: Selected providers test a sample of patients who have ILI each week and laboratory tests identify which specific viruses caused the illness. Deaths with Pneumonia or Influenza Mentioned on the Death Certificate, Virginia, 2009-10 Influenza Season Compared with 2008-09 Season Influenza Dashboard 200 180
160 N um ber of D eaths 140 120 100 80 60 40 20 0 Week Ending Date 2008-09 Flu Season
2009-10 Flu Season Percent of Emergency Department and Urgent Care Visits for Influenza-like Illness (ILI) by Age Group, Virginia, 2008-09 and 2009-10 Influenza Seasons 30.0 Percent of Visits for ILI 25.0 20.0 15.0 10.0 5.0
0.0 0-4 Positive Laboratory Reports* and ILI Visits by Week, Virginia, 2008-09 and 2009-10 Influenza Seasons 1000 65+ All Ages Percent of Emergency Department and Urgent Care Visits for Influenza-like Illness (ILI) by Week, Virginia, 2009-10 Influenza Season Compared with the Previous Two Seasons
16.0 16 900 14.0 14 800 10.0 600 500 8.0
400 6.0 300 4.0 200 12 Percent of Visits for ILI 12.0 700
Percent of Visits with ILI 10 8 6 4 2 2.0 100 10 10 /4/2 /2 0
1 5/ /10 22 6/ /10 12 / 7/ 10 3 7/ /10 24 /1 0 Week Ending Date B
A/Unknown A Seasonal** A/H1, Seasonal A/H3 2009 H1N1 ILI Activity *Positive laboratory reports are presented by week of specimen collection. Data are added as new test results become available; therefore, information for the most recent week will always be incomplete. ** 'A Seasonal' indicates a positive Influenza A finding that is negative for Novel H1N1 with no further subtyping. Week Ending Date
2007-08 2008-09 2009-10 10 /2 9/ 11 8/ 21 7/ 31
7/ 10 6/ 19 5/ 8 5/ 29 4/ 17 3/
6 3/ 27 2/ 13 1/ 2 1/ 23 12 /1 2
11 /2 1 0.0 10 /3 1 0 0 10 /1
0 Number of Positive Labs Reports Week Ending Date 25-49 50-64 5-24 Syndromic Surveillance Uses pre-diagnostic indicators to identify emerging health problems Self medication Medical
care Diagnosis Insurance billed Onset of symptoms Medical consultation Laboratory testing Prescription filled
Automating Syndromic Surveillance Began as manual activity just after 9/11/01 Automated in 2004 with ESSENCE Electronic Surveillance System for the Early Notification of Community-Based Epidemics (Johns Hopkins University, Applied Physics Laboratory) Access limited to approved VDH staff Collaborate with District of Columbia and Maryland to monitor national capital region ESSENCE Hospital emergency departments and urgent care centers electronically transmit chief complaints to secure VDH server every day Receive chief complaints from ~9,500 patient
visits each day System also includes: Over-the-counter drug sales School attendance Syndromes Complaints tallied into syndrome categories Death
Sepsis (serious infection) Rash Respiratory (e.g., cough) Gastrointestinal (e.g., diarrhea) Unspecified Infection (fever) Neurological (e.g., dizziness) Other Syndromic Analyses Automated analyses identify unusual patterns and increases are investigated Drill Down Ability Animal bites Uses of Syndromic Data Monitor trends in influenza, gastrointestinal illness
Detect outbreaks or individual cases of disease, especially illnesses with unique symptoms or names (e.g., scombroid poisoning) Special event surveillance (e.g., Olympic Games, Presidential Inauguration, National Boy Scout Jamboree) Disaster surveillance (e.g., hurricanes, ice storms, etc.) Exposure Detection U.S. Postal Services BioHazard Detection System Tests for anthrax in mail sorting area every hour Selected Post Offices in Virginia Response is collaborative Homeland Security/DOD BioWatch System
DC area, including northern Virginia Central Virginia around Richmond Eastern Virginia around military bases Monitors for biologic agents atop buildings Data Source: Surveys If done continually or periodically, can monitor risk factors and changes in prevalence over time Can also assess knowledge, attitudes People usually queried only once and not monitored on an individual basis after that
From questionnaires, interviews (in person or telephone), or record review National Surveys www.cdc.gov/nchs National Health Interview Survey Random selection of households In-home interview gathering information on all in the household Self-reported illnesses, chronic conditions, injuries, impairments, use of health services Civilian, non-institutionalized population National Surveys, continued National Health and Nutrition Examination Survey (NHANES) Prevalence of chronic conditions, distribution of
physiologic and anthropomorphic measures, and nutritional status for representative samples of the U.S. population National Health Care Survey, includes National Hospital Discharge Survey National Ambulatory Medical Care Survey BRFSS Behavioral Risk Factor Surveillance System Random digit telephone surveys on noninstitutionalized adults health behavior and use of prevention services Height, weight, physical activity, smoking, alcohol use, seatbelt use, cholesterol screening, mammography, etc. Done in most states (including Virginia) CDC program
BRFSS Charts PRAMS Pregnancy Risk Assessment Monitoring System Assesses maternal attitudes and experiences before, during, and shortly after pregnancies that resulted in a live birth. In Virginia, about 100 mothers of 2-6 month old infants are randomly selected each month from birth certificate data. Eligible mothers are mailed surveys, and phone interviews are conducted if a survey is not returned Survey does not represent pregnancies that resulted in induced termination.
Reasons for Not Using Birth Control Before Pregnancy Among Women Not Trying to Become Pregnant, VA PRAMS, 2008-09 Other Survey Examples Exit interviews at health facilities Special studies Risk-behavior Cluster surveys Rapid surveillance after emergencies Data Source: Administrative Data Routinely collected for other reasons. E.g., hospital discharge data collected for billing purposes, Medicaid and Medicare
data, emergency department data, data collected by managed care organizations. Virginia Health Information (VHI) maintains our states hospital discharge database. Causes of Injury Death, Virginia, 2009 From Hospital Discharge Data Mechanism Number of Deaths Population Rate Age Adjusted Rate
Struck by, against TOTAL 3,798 http://www.vahealth.org/Injury/voirs/reports/DeathRates.aspx Usefulness of Administrative Data Depends on: What information is computerized Standardization of codes for diagnoses, symptoms, procedures, reasons for the visit Time between occurrence of health event and availability of data Ability to link with other data systems
Whether supplementary information can be obtained Data Sources We Covered Vital Statistics Notifiable Diseases Registries Sentinel Surveillance Syndromic Surveillance Surveys
Administrative Data Other Important Surveillance Systems Injury Diabetes Child/Adolescent Hospitalizations Special temporary systems Drug safety
Food safety Etc. Public health collects a lot of information on the health of our communities! Analysis of Surveillance Data Line list of cases include demographic and clinical info, risk factors, lab results, etc Descriptive epidemiology Person: age, race/ethnicity, sex Place: county, district, state Time: day, month, year onset vs. reported Incidence and prevalence Rates -- crude, specific, standardized Trends and seasonality Geographic clustering (maps)
Graphics Used to Describe Data Interpretation of Surveillance Data Limitations Under-reporting Biased reporting Inconsistent case definitions Consider context Seasonality Recent policy changes or interventions Interpretative Uses of Surveillance Data
Identifying epidemics Identifying new syndromes or risk groups Monitoring trends Evaluating public policy Projecting future needs Data Dissemination What should be said? To whom? Through what communication medium? How should the message be stated? What effect did the message create? Determine answers based on the purpose of
the system. SOCO - single overriding communication objective. [What is new? Who is affected? What works best?] Data Dissemination MESSAGE AUDIENCE CHANNEL Evaluating Surveillance Systems System objectives and usefulness Actions taken as a result of the data. Does the system do what its supposed to do?
Operation of the system Who is reporting? To whom? What information is collected? How is information stored? Who analyzes the data? What are the findings? How often are reports disseminated? to whom? Cost Evaluation - System Attributes Simplicity Should be as simple as possible and as easy to operate as possible. Flexibility Should be able to adapt to changing needs.
Acceptability Willingness of individuals or organizations to participate in the surveillance system. (Judge based on completeness, timeliness, reporting) Evaluation - System Attributes Sensitivity Proportion of cases detected by the system. Completeness of reporting. Detect epidemics? Increased awareness, new diagnostic test, change in surveillance method may impact. Predictive Value Positive Proportion of persons identified as having the disease who actually have it. Sensitivity/Specificity and
Predictive Value +/- (PVP/PVN) Detected by Surveill Condition Present Yes No Yes True positive
Representativeness Do the characteristics of reported events compare favorably with those in the population. Is there case ascertainment bias? Bias in descriptive information about a reported case? Timeliness Any delay between the steps? (onset, diagnosis, report to public health, disease control actions) CDC Guidelines for Evaluating Public Health Surveillance Systems: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5013a1.htm Ethical and Legal Issues Relating to Surveillance Professional obligations Protecting confidentiality and privacy
Informed consent Mandated activity vs. research Maintaining public trust Right of Access Conclusion Surveillance provides information on the health of the community Public health relies on information from medical care providers and takes preventionoriented actions based on information received Surveillance involves taking information in, analyzing & interpreting it, and disseminating it to those who need it Contact Information
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