Public Health Surveillance Systems

1
Public Health Surveillance Systems
2
Goals

• Adverse events surveillance
• Syndromic surveillance
• Registries
• Laboratory data

• Review purpose of surveillance
• Describe types of state and local surveillance
  systems
• Vital records
• Disease reporting
• (morbidity data)
• Surveys
• Sentinel surveillance
• Zoonotic disease
• surveillance
• Provide example of public health actions
  resulting from surveillance data

3
Purpose of Surveillance

• Collecting surveillance data has many purposes
• Monitoring disease trends
• Detecting outbreaks
• Providing information to plan public health
  interventions
• Stimulating research

4
Purpose of Surveillance

• Specific uses of surveillance data vary depending
  on organization or agency
• National agencies
• Monitoring disease trends over time to inform
  policy
• State and local agencies
• Assuring accurate diagnosis and treatment of
  infected persons
• Managing people exposed to disease
• Detecting outbreaks
• Guiding public health prevention and
  control programs

5
Types of State and Local Surveillance Systems

• Surveillance systems used to monitor disease
  trends and plan public health programs
• Vital statistics, disease reporting, surveys
• More specialized systems
• Sentinel surveillance, zoonotic disease
  surveillance, adverse events surveillance,
  syndromic surveillance, disease registries,
  laboratory surveillance
• Some types more useful for certain diseases than
  others each fills a specific need

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Vital Statistics

• Records of births and deaths a basic but
  critical cornerstone of public health
  surveillance
• Mortality data over past century show decrease in
  rate of deaths due to infectious diseases rate
  of death from non-infectious causes remain steady
  
• Infant mortality rate (number of deaths among
  infants per 1,000 births) long used as indicator
  of overall population health
• Birth data used to monitor incidence of preterm
  birth, risk factor for variety of adverse health
  outcomes

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Vital Statistics

• In United States, vital statistics available from
• National Center for Health Statistics
• State vital records offices
• CDC WONDER online system containing data on
  births, deaths, many diseases from Centers for
  Disease Control and Prevention (CDC)

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Disease Reporting (Morbidity Data)

• Disease reporting required internationally by
  World Health Organization through International
  Health Regulations
• Smallpox
• Wild-type poliomyelitis
• Severe acute respiratory syndrome (SARS)
• Human influenza caused by new subtypes
• Any public health emergency of international
  concern
• Broad definition used to capture any disease,
  condition, event that could represent
  international risk

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Disease Reporting (Morbidity Data)

• In the United States, disease reporting mandated
  by state law
• List of reportable diseases varies by state
• States report nationally notifiable diseases to
  CDC on voluntary basis
• List of notifiable diseases updated regularly by
  Council of State and Territorial Epidemiologists
  and CDC

10
Surveys

• Especially useful for monitoring chronic diseases
  and health-related behaviors
• Youth Risk Behavior Survey (YRBS) asks high
  school students about substance use, sexual
  behavior, physical activity, nutrition
• Results used to monitor trends in health
  behaviors, plan public health programs, evaluate
  public health policies at national and state
  levels

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Surveys
Percent of high school students who reported
smoking in the 30 days prior to the survey,
United States, 1997-2007 

• YRBS shows decline in youth smoking from 36 in
  1997 to 20 in 2007

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Surveys

• Other national surveys conducted by CDC
• Behavioral Risk Factor Surveillance System
  (BRFSS)
• National Health Interview Survey (NHIS)
• Pregnancy Risk Assessment Monitoring System
  (PRAMS)
• National Health and Nutrition Examination Survey
  (NHANES)

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Sentinel Surveillance

• Alternative to population-based surveillance,
• Involves collecting data from sample of reporting
  sites (sentinel sites)
• Example Selected health care providers report
  number of cases of influenza-like illness to
  state health department on weekly basis
• Allows states to monitor trends using relatively
  small amount of information

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Sentinel Surveillance
Percentage of visits for influenza-like illness
reported by US sentinel provider network,
2006-2007, 2007-2008

• Graph indicates peak of influenza activity during
  2007- 2008 season in late February and
  early March (Weeks 7-9)

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Sentinel Surveillance

• Sentinel providers also used to gather more
  specific information
• Example sentinel provider network in British
  Columbia, Canada, used in a study of vaccine
  effectiveness during 2005-2006 influenza season

16
Zoonotic Disease Surveillance

• Surveillance of zoonotic diseases (diseases found
  in animals that can be transmitted to humans)
  often involves system for detecting infected
  animals
• Example 2001 Florida surveillance for West Nile
  Virus (WNV)
• Web site and telephone hotline to report dead
  birds, some collected and tested for WNV
• Mosquitoes collected and tested for WNV in 10
  counties
• Blood collected from 3-12 sentinel chickens in
  each of 212 flocks up to 4 times per month,
  tested for antibodies to WNV
• Veterinarians asked to test horses with
  neurologic symptoms consistent with WNV
• Health care providers reminded of reporting and
  diagnostic criteria for possible human cases of
  WNV

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Zoonotic Disease Surveillance

• Surveillance systems allowed public health
  authorities to determine intensity of WNV by
  geographic area
• Detection of WNV led to public health control
  measures
• Advising public to protect against mosquito bites
• Intensifying mosquito abatement efforts

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Adverse Events Surveillance

• Surveillance system focusing on patient safety
  Adverse Events Reporting System (AERS), operated
  by Food and Drug Administration (FDA)
• Negative effects experienced by people who
  received approved drugs, therapeutic agents
• Voluntary reports from health care providers
  (physicians, pharmacists, nurses) and public
  (patients, lawyers)
• Health care providers/patients may report events
  directly to product manufacturer manufacturer
  required to report event to AERS
• FDA uses AERS to identify possible safety
  concerns associated with approved products

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Adverse Events Surveillance

• Vaccine Adverse Events Reporting System (VAERS)
  also focused on patient safety operated by CDC
  with FDA
• Like AERS, but for negative effects experienced
  by people who have received licensed vaccines
• Used in 2003 for smallpox vaccines to health care
  and public health professionals in preparation
  for bioterrorist attack
• gt100 adverse events reported after smallpox
  vaccination, 16 suspect and 5 probable cases of
  myocarditis or pericarditis
• Advisory Committee on Immunization Practices
  recommended ending vaccination after health
  care and public health response teams

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Adverse Events Surveillance

• Passive surveillance systems may be limited by
  underreporting or biased reporting, cannot be
  used to determine whether a drug or vaccine
  caused a specific adverse health event
• (See FOCUS Volume 5, Issue 5 for definitions of
  active and passive surveillance)
• Used as early warning signals
• Possible associations between drugs or vaccines
  and adverse events examined using well designed
  epidemiologic study, appropriate action based on
  results

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Syndromic Surveillance

• Relatively new surveillance method, uses clinical
  information about disease signs and symptoms,
  before diagnosis is made
• Often use electronic data from hospital emergency
  rooms

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Syndromic Surveillance

• Example New York City operates syndromic
  surveillance system using emergency department
  chief-complaint data from approximately 44
  hospitals
• Data monitored electronically for beginning of
  disease outbreak
• In 2002, system detected higher than usual number
  of diarrheal and vomiting symptoms
• Health department notified hospital emergency
  departments of possible outbreak and collected
  stool specimens, several tested positive for
  norovirus

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Syndromic Surveillance

• Example New York City (continued)
• Similar outbreak later that year not detected by
  the system
• Failure to detect attributed to incorrect coding
  of chief complaint by emergency departments
• Illustrates potential benefits of syndromic
  surveillance, areas where changes needed to
  increase usefulness of system

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Registries

• Surveillance system used for particular
  conditions
• Often established at state level to collect
  information about persons diagnosed with
  condition
• Example cancer registries collect information
  about type of cancer, anatomic location, stage of
  disease at diagnosis, treatment, outcomes
• Used to improve prevention programs
• Example women in rural areas diagnosed with
  breast cancer later than women in urban areas
  choose to promote mammography screening
  in rural areas using mobile van

25
Laboratory Data

• Public health laboratories routinely conduct
  tests for viruses, bacteria, other pathogens
• In US, labs participate in National Salmonella
  Surveillance System through electronic reporting
  of Salmonella isolates
• 2006 gt40,000 isolates reported
• Lab serotyping provides information about cases
  likely to be linked to common source
• Serotypes are useful for detecting local, state,
  or national outbreaks

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Laboratory Data

• Another lab system PulseNet by CDC and
  Association of Public Health Laboratories to
  monitor foodborne illness outbreaks
• Enables labs across US to compare pulsed-field
  gel electrophoresis (PFGE) patterns of bacteria
  from ill persons and determine similarity
• Allows scientists to determine whether outbreak
  is occurring, even at geographically distant
  locations
• Can decrease time required to identify outbreaks
  of foodborne illness and causes

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Public Health Actions Resulting From
Surveillance Poliomyelitis

• Global example monitoring progress toward
  eradication of poliomyelitis

• Dramatic decrease in paralytic poliomyelitis in
  US following licensure of inactivated polio
  vaccine (1955), oral polio vaccine (1961)

Number of cases of paralytic poliomyelitis by
year, United States, 1967-1997 
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Public Health Actions Resulting From
Surveillance Poliomyelitis

• Global example monitoring progress toward
  eradication of poliomyelitis (continued)
• Using data from countries around world, World
  Health Organization implemented intensive
  vaccination programs where decline not as
  significant

29
Public Health Actions Resulting From
Surveillance HIV/AIDS

• Example surveillance for HIV/AIDS ongoing since
  detection of disease in the US in 1981
• Data on incidence and prevalence among population
  subgroups, geographic areas important to guide
  prevention, control efforts
• 2003-2006 estimated number of cases increased
  among men who have sex with men, remained steady
  among heterosexuals, decreased among injection
  drug users
• Suggests that prevention programs working more
  effectively in some groups than others   

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Public Health Actions Resulting From
Surveillance HIV/AIDS

• Mapping rates shows clear pattern of higher risk
  in southeastern states than in rest of nation
• Suggests need for more prevention measures in
  southeast

Rates of diagnosed HIV/AIDS, by area of
residence, United States, 2006 
31
Conclusion

• Many sources of public health surveillance data
  at local, state, national levels
• Knowing where to look for different types of data
  can save time and resources
• Data used for variety of purposes
• Guiding prevention strategies and targeting
  resources
• Detecting disease outbreaks of local, national,
  international significance
• Evaluating control measures

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Resources

• National Vital Statistics System
• Data on births, deaths, marriages, divorces,
  fetal deaths from all 50 states, 2 cities
  (Washington, DC, and New York City), 5
  territories (Puerto Rico, Virgin Islands, Guam,
  American Samoa, Commonwealth of the Northern
  Mariana Islands) much of information available
  online
• http//www.cdc.gov/nchs/nvss.htm
• CDC WONDER
• User-friendly query system providing public
  health information on births, deaths, cancer
  incidence, HIV and AIDS, tuberculosis,
  vaccinations, census data
• http//wonder.cdc.gov/
• Nationally Notifiable Infectious Diseases
• List of diseases recommended for states to report
  to CDC
• http//www.cdc.gov/ncphi/disss/nndss/phs/infdis.ht
  m

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References

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   RE, eds. Principles and Practice of Public
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2. Armstrong GL, Conn LA, Pinner RW. Trends in
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4. Centers for Disease Control and Prevention.
   Summary of notifiable diseases United States,
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5. Centers for Disease Control and Prevention.
   Cigarette use among high school students United
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   200857(25)689-691.

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References

1. FluView. Outpatient illness surveillance. Centers
   for Disease Control and Prevention Web site.
   http//www.cdc.gov/flu/weekly/. Updated October
   10, 2008. Accessed October 14, 2008.
2. Skowronski DM, Masaro C, Kwindt TL, et al.
   Estimating vaccine effectiveness against
   laboratory-confirmed influenza using a sentinel
   physician network results from the 2005-2006
   season of dual A and B mismatch in Canada.
   Vaccine. 200725(15)2842-2851.
3. Blackmore CGM, Stark LM, Jeter WC, Oliveri RL,
   Brooks RG, Conti LA, Wiersma ST. Surveillance
   results from the first west nile virus
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4. Food and Drug Administration, Center for Drug
   Evaluation and Research. Adverse Event Reporting
   System (AERS) Web site. http//www.fda.gov/cder/ae
   rs/default.htm. Published August 7, 2002.
   Updated September 5, 2008. Accessed November 21,
   2008.

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References

1. Zhou W, Pool V, Iskander JK, et al. Surveillance
   for safety after immunization vaccine adverse
   events reporting system (VAERS) United States,
   1991-2001. MMWR CDC Surveill Summ.
   200352(SS-1)1-11.
2. Centers for Disease Control and Prevention.
   Update adverse events following civilian
   smallpox vaccination United States, 2003. Morb
   Mortal Wkly Rep. 200453(5)106-107.
3. Centers for Disease Control and Prevention.
   Advisory Committee on Immunization Practices
   (ACIP) statement on smallpox preparedness and
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   2003. Accessed October 23, 2008.
4. Steiner-Sichel L, Greenko J, Heffernan R, Layton
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   200453(suppl)190-195.

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References

1. Centers for Disease Control and Prevention.
   Salmonella surveillance annual summary, 2006.
   http//www.cdc.gov/ncidod/dbmd/phlisdata/salmonell
   a.htm. Published 2008. Accessed October 14,
   2008.
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3. Centers for Disease Control and Prevention. What
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   http//www.cdc.gov/pulsenet/whatis.htm. Published
   July 24, 2006. Accessed December 3, 2008.
4. Centers for Disease Control and Prevention.
   Summary of notifiable diseases, United States,
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5. Centers for Disease Control and Prevention.
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