Lecture 9 : Surveillance

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Epidemiology

• Lecture 9 Surveillance

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Learning outcomes

• Describe the use of surveillance in monitoring
  the health of the community
• Define the keys elements of a health surveillance
  system
• Interpret surveillance data
• Describe key data sources for health surveillance

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Public Health Approach
Implementation How do you do it?
Intervention Evaluation What works?
Problem
Response
CDC, 2001
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Surveillance

• is the continuous and systematic collection,
  analysis, interpretation and dissemination of
  descriptive information for monitoring health
  problems
• asks the question What is the problem?

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Surveillance systems

• Include networks of people and activities that
  maintain the surveillance process
• May function at a range of levels, from local to
  international

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Objectives of Surveillance

• Describe the epidemiology of health problems and
  issues
• Monitor the occurrence of disease/ health event
  indicators over time within specific populations
• Links to planning and provision of services
• Education and policy
• Evaluation of interventions (control and
  prevention)
• Project changes
• Detect outbreaks/ epidemics
• Stimulate research

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Elements of a Surveillance System

• Case definition e.g. WHO
• Population under surveillance
• Cycle of Surveillance
• Confidentiality
• De-identified core unit data are supplied
  fortnightly for collation, analysis and
  dissemination
• Anonymous
• Coded
• Incentives to participation

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Example Hepatitis A Case Definition

• Notifications
• a) Detection of anti-hepatitis A virus IgM
  antibody, in the absence of recent vaccination
• or
• b) A clinical case of hepatitis (jaundice
  elevated aminotransferase levels, without a
  non-infectious cause) and an epidemiological link
  to a serologically confi rmed case.
• Hospitalisations and deaths
• The ICD10AM/ICD10 codes B15 (hepatitis A) were
  used to identify hospitalisations and deaths

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Cycle of Surveillance
Collect
Analyse
Link to practice
Interpret
Disseminate
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Information Loop of Public Health Surveillance
Analysis
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Approaches to surveillance

• Notifiable disease reporting
• Laboratory-based reporting
• Sentinel surveillance and surveys
• Special surveillance networks Volunteer
  providers
• Active and passive surveillance
• Disease Registries
• Birth, Death Registers
• Information systems (Administrative data)
• Environmental monitoring
• Record linkages

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• Record linkage brings together information from
  two independent source records believed to relate
  to the same individual or family and is critical
  for creating an information-rich environment.

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Approaches to surveillance

• Notifiable disease reporting
• Collation of reports about a disease that must
  be reported to the authorities by law or
  ministerial decree.

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NNDSS

• The National Notifiable Diseases Surveillance
  System (NNDSS) was established in 1990 under the
  auspices of the Communicable Diseases Network
  Australia (CDNA).
• The System co-ordinates the national surveillance
  of more than 50 communicable diseases or disease
  groups.
• Computerised, de-identified unit records of
  notifications are supplied to the Department of
  Health and Ageing for collation, analysis and
  publication on the
• Internet and
• quarterly journal Communicable Diseases
  Intelligence.

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• Notification data provided include
• a unique record reference number
• state or territory identifier
• disease code
• date of onset
• date of notification to the relevant health
  authority
• sex
• age
• Indigenous status
• postcode of residence

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• The quality and completeness of data compiled in
  the National Notifiable Diseases Surveillance
  System are influenced by various factors.
• Notifications may be required from treating
  clinicians, diagnostic laboratories or hospitals.
  
• In addition, the mechanism of notification varies
  between States and Territories and in some cases
  different diseases are notifiable by different
  mechanisms.
• The proportion of cases seen by health care
  providers which are the subject of notification
  to health authorities is not known with certainty
  for any disease, and may vary among diseases,
  between jurisdictions and over time.

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(No Transcript)
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Approaches to surveillance

• Laboratory-based reporting The starting point is
  the identification or isolation of a particular
  organism in a laboratory. For example
  surveillance of Salmonellosis
• For example HIV/AIDS
• National surveillance for HIV disease is
  coordinated by NCHECR, in collaboration with
  State and Territory health authorities and the
  Commonwealth of Australia.
• Cases of HIV infection are notified to the
  National HIV Database on the first occasion of
  diagnosis in Australia, by
• either the diagnosing laboratory (ACT, New South
  Wales, Tasmania, Victoria) or
• by a combination of laboratory and doctor sources
  (Northern Territory, Queensland, South Australia,
  Western Australia)

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Sentinel surveillance and surveys

• The surveillance of a specified health event in a
  sample of the population at risk. The sample
  should be representative of the total population
  at risk.
• Monitoring of key health events through sentinel
• Sites
• Events
• Providers
• Vectors/animals

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• Sentinel Sites
• Sentinel Sites might be medical clinics,
  hospitals, health centres which cover certain
  populations at risk.
• They could be networks of individual
  practitioners such as primary health care
  physicians.
• Such sentinels can often provide an early
  assessment of occurrence in an outbreak and are
  most useful for diseases that occur frequently.
• Sentinel Providers
• Physician sentinels are often used for
  surveillance of influenza.
• However, in some instances, physician networks
  can be used to detect rare events such as acute
  flaccid paralysis.

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• Sentinel Events
• Sentinel events are measured occurrences that can
  be used to bring attention to problems in
  practices, procedures or systems.
• For example, maternal mortality has long been
  used as one indicator of the efficacy of maternal
  and child health programmes.
• Sentinel vectors/animals
• For example sentinel chicken surveillance
  program for West Nile virus infection
• Sentinel surveillance is a means to provide
  information for mosquito control to be more
  effective

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• Sentinel general practitioner surveillance
  schemes for influenza monitor the consultation
  rates for influenza-like illness (ILI).
• In Australia, there are 5 such schemes
• the Australian Sentinel Practice Research Network
  (ASPREN) which collects data at a national level
• the New South Wales Influenza Surveillance
  Scheme,
• the Victorian Influenza Surveillance Scheme,
• Western Australian sentinel general practices
• the Northern Territory Tropical Influenza
  Surveillance Scheme.
• ASPREN and the Northern Territory Tropical
  Influenza Surveillance Scheme report ILI rates
  throughout the year,
• while the other sentinel surveillance schemes
  report from May to October each year.

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• In 2003, an average of 47 (range 3262) general
  practices reported ILI cases on an average of
  4,962 (range 2,1386,587) consultation per week.

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Sentinel surveillance and surveys
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Approaches to surveillance

• Special surveillance networks
• Set up to monitor specific health events often
  for short term specific purpose
• eg
• World Cup
• Hospital Infection Surveillance system

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Approaches to surveillance

• Active surveillance
• The dynamic seeking of data from participants in
  the surveillance system on a regular basis. It is
  labour intensive, costly and seldom done e.g.
  personal visits, telephone calls to obtain
  required data
• Health department initiated
• Passive surveillance
• Surveillance where reports are awaited and no
  attempt made to actively seek reports from the
  participants in the system. Most common form of
  surveillance. Mandatory
• Provider initiated

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Approaches to surveillance

• Disease Register
• is a list of patients with a given condition.
• eg Diabetes, Cancer
• Birth, Death Registers
• Information systems (Administrative data)
• Environmental monitoring
• Record linkages

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Attributes of surveillance systems

• Sensitivitydoes the SS identify all events in a
  target pop?
• Timeliness the length of time it takes to
  complete the entire information cycle
• Representativeness does the SS represent all the
  cases in the target pop? (only identifying
  extreme cases rather then all cases)
• Predictive value are the reported cases really
  cases?

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Attributes of surveillance systems ctd.

• Accuracy and completeness of descriptive
  information is the information reliable and
  descriptive in terms of potential exposure and
  high risk situations?
• Simplicity is the method of data collection
  unobtrusive, user friendly, easy to complete
  (forms)?
• Flexibility can the SS adapt to monitoring new
  standards of disease/information?
• Acceptability is the SS accepted by the
  participants?

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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Portray the natural history of a disease
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in infectious agents
• Detect changes in health practices
• Facilitate planning

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Asthma in Australia 2003

• http//www.asthmamonitoring.org/

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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Estimated prevalence of National Health Priority
Area diseases/conditions, all ages, Australia,
2001
Source ABS National Health Survey 2001.
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Trends in the prevalence of asthma,adults,
Australia, 19902001
Sources Comino et al. 1996 Taylor et al. 1998
Wilson et al. 2002, 2003 Woods et al. 2001.
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Prevalence of current asthma, by age group and
sex, Australia, 2001
Source ABS National Health Survey 2001.
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Death rates for asthma,all ages and age 534
years, by sex,Australia, 19792001
Source AIHW National Mortality Database.
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Children with and without current asthma with one
or more cigarette smokers in the household, by
age group and sex, Australia, 2001
Source ABS National Health Survey 2001.
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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Asthma Mortality Rates, by health service area,
United States,1995-97
National, Heart, Lung Blood Institute.
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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Asthma-related health care encounters, per
100,000 population, Australia and New South
Wales, 19982002
Sources BEACH Survey of General Practice AIHW
National Hospital Morbidity Database NSW Health
Department Emergency Department Collection (EDDC)
(HOIST) Centre for Epidemiology and Research, NSW
Department of Health.
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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Number of structured general practice asthma
review visits, all ages and age 5 to 34 years,
Australia, Oct 2001 - June 2003
Source MBS statistics.
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Claims for the performance of spirometry and
complex lung function tests which included
spirometry, all ages, Australia, 19942002
Source HIC health statistics.
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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Children with and without current asthmawith one
or more cigarette smokers in the household, by
SEIFA quintile, age 0 to 14 years, Australia, 2001
Source ABS National Health Survey 2001.
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Pollen Map, US
Source Allergy Health Centre
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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning

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Changes over time in the proportion of people
with asthma who report possession of a (written)
asthma action plan, Australia, 19902001
Sources Comino et al. 1996 Gibson et al. 2000,
Public Health Division 2001 Wilson et al. 2002,
2003.
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Proportion of people with current asthma with a
written asthma action plan, by age group and sex,
Australia, 2001
Source ABS National Health Survey 2001.
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Emergency Department presentations for asthma per
100,000 population, by month and age group, New
South Wales, January 1998 to March 2003
ED presentations for asthma per 100,000 population
Source NSW Health Department Emergency
Department Data Collection (HOIST), Centre for
Epidemiology and Research, NSW Department of
Health.
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Hospital separations for asthma,per 100,000
population, Australia, 19932001
Source AIHW National Hospital Morbidity Database.
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Uses of Public Health Surveillance

• Estimate magnitude of the problem
• Determine geographic distribution of illness
• Detect epidemics/define a problem
• Generate hypotheses, stimulate research
• Evaluate control measures
• Monitor changes in risk factors or causal agents
• Detect changes in health practices
• Facilitate planning