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10-29-a Public Health Surveillance, Public Health Law, and Epidemics (outbreak investigation)
- Assessment
- Policy development
- Assurance
- Ten essential Public health services
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Federal Basis: .
- Commerce Clause – interstate commerce – feds can regulate the drugs here
- Taxing and spending power – granting or withholding federal funds
- State Basis: .
- Police power – Threat to society
- “parens patriae” (state act as father) – threat to self
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Surveillance
- Establish baseline data: Estimate magnitutde, determine geographic distribution
- Evaluate time trends: long-term secular trends; seasonal variation – mode of transmission
- Identify outbreaks: disease outbreak is occurrence of disease at unexpectedly high frequency; epidemic threshold
- Evaluate control measures: vaccination
- Set disease control priorities: monitor changes in infectious disease agents; detect changes in health practices; facilitate planning
- Generate hypothesis/research: MDR tuberculosis and AIDS; stimulate research – vaccines
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Surveillance: Establish baseline data: Estimate magnitutde, determine geographic distribution
- Necessary for detection of epidemics
- Analysis by
- Time: date or hour of onset of illness
- Person: characteristics such as age
- Place: geographic area
- Gives an idea where and on whom might want to focus screening and prevention to prevent the spread of an epidemic
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Morbidity – prevalence
- Proportion (not rate) of individuals in a population who have disease for a specific time period
- P = k * #existing cases of disease / total population
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Morbidity – incidence
- Number of new cases in a population of a specific time
- I = k * number of new cases in specified time period / total population at risk
- Used more in iteologic studies
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Selected sources of Data
- Environmental monitoring systems
- Animals/vectors
- Individuals
- Laboratories
- Medical Records
- Administrative records
- Police records
- Birth/death certificates
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Data sources and methods for surveillance
- Notifiable diseases
- Lab speciments
- Vital records
- Sentinel surveillance
- Registries
- Surveys
- Administrative data systems
- Other data sources
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Responsibility for surveillance
- Federal: Centers for Disease Control and Prevention
- State: state agency
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Surveillance Activities
- Passive surveillance: NY state Dept. of Health waits for report from physicians, labs, hospitals
- Active surveillance: NY State Dept. of Health calls health care providers
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Infectious Disease Surveillance in New York State
- About 50 legally reportable communicable disease
- Notifiable disease if link between case report and public health action
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New York State Communicable Disease Data Sources
- Physicians: case reports
- Laboratories: lab specimen reports
- Hospitals: case reports
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New York State reporting
- Report to local county or city health department except AIDS/HIV
- Then local dept. reports to New York State
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Chronic Disease Data Sources:
- Viral records: death certificates, computerized database
- Registries: cancer registries; hospital-based with medical record review
- Surveys: behavioral risk factor surveillance system (BRFSS); state-based telephone survey
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National Notifiable Disease Surveillance
Report to local, local reports to State, reports transmitted to CDC primarily through an electronic dsease surveillance system (National Electronic Disease Surveillance System) – NEDSS: .
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Current status: National Notifiable Diseases Surveillance System (NNDSS)
- CSTE/CDC collabotation
- List revised at annumal CSTE meeting
- Voluntary reporting by states to CDC
- Reporting mandated at state level
- Reportable diseases vary by state
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National non-infectious disease surveillance
- Death rates across the country, births, deaths, marriages, divorces
- National Infant Mortality Surveillance (NIMS):
- Linked birth and infant death data; and the National Death Index
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Use of NCHS Data systems for Surveillance
- Population-based surveys:
- National health interview survey
- National health and nutrition examination survey
- Provider-based surveys:
- National hospital discharge survey
- National ambulatory medical care
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Limitations of Surveillance
- Completeness, accuracy, and representativeness of data
- Underreporting
- Lack of telephones, small sample of minorities
- Latency period of data
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National HIV Case Sruveillance
- Advances antiretroviral therapy: slowed progression of disease and decline in AIDS 1996
- New treatment for HIV infection
- AIDS trends not representative of HIV trends
- CDC recommends surveillance
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Invesitgating outvreaks
- Epidemic: upon the population
- Endemic: disease at usual level
- Purpose of investigation: describe outbreak; attack rate = new cases/ exposed persons
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How to conduct an outbreak investigation
- Establish the diagnosis
- Establish the case definition – specific criteria – symptoms, lab, epidemiology – location, contacts
- Determine whether an epidemic exists: look for unreported cases; determine population at risk; ongoing surveillance
- Characterize the epidemic by: place, person, time
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Questions regarding time: epidemic curve exercise
- What is the index case?
- What is the incubation period?
- When was the exposure?
- What is the type of exposure?
- Common source vs propagated?
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Outbreak investigation
- Develop hypotheses about disease transmisson: source and pattern of spread
- Test the hypotheses: cases vs controls; question cases, laboratory studies
- Initiate control measures: sanitation, prophylaxis (vaccination), Dx and treatment, control of disease vector
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