Disease Surveillance and Monitoring Systems

Syndromic surveillance: An alert is issued when ...

Case counts reach threshold

Surveillance: proving a disease is present

Case finding Measure level of disease

Passive surveillance systems used to monitor biological agents

Case-based (animals and people) Syndromic (people, sometimes animals)

Surveillance: systematic ___, ___, and interpretation of data and the ___ of information to those who need to know in order to ___

Collection Analysis Dissemination Take action

Why is surveillance important?

Control and/or prevent disease -any data collected must be organized and carefully examined -any results need to be communicated to stakeholders

Types of sampling: non probability sampling

Convenience sampling

Reasons to sample populations

Describe the characteristics of a population Test specific hypotheses

Sampling steps

1. Define objectives 2. ID target population 3. Determine required precision 4. Decide sampling units 5. Develop sampling frame

Monitoring is surveillance without ...

A threshold

PASSIVE//ACTIVE surveillance systems may have high levels of completeness but are usually much more expensive to maintain

Active

Surveillance often targets ___ for which a rapid, direct, predetermined action is warrented

Agents/diseases *maximize early detection and minimize false-positives

Passive surveillance utilizes samples or observations collected primarily for ...

Another purpose

For early detection, the surveillance system should ...

Be continuous Have comprehensive coverage of the population Be sensitive w/a very low design prevalence

Example of syndromic surveillance

BioSense program (CDC): syndromes created for BT-related and non-related infectious agents -compares baselines (expected) to observed count of visits for the current day

Active surveillance systems used to monitor for biological agents

Biosensor (environment) Pathogen screening (animals, sometimes people)

Surveillance to "measure disease" DOES//DOESN'T need to be continuous, should be based on ____ sampling to avoid bias, and should use a big enough sample size to give ____

Doesn't (can be ad how or periodic) Representative sampling Adequate precision

Surveillance to demonstrate freedom from disease DOES//DOESN'T need to be continuous and can use ____ sampling to increase efficiency as well as uses a LOWER//HIGHER design prevalence than early detection

Doesn't (instead may be ad hod or intermittent) Risk-based Higher

Surveillance: proving a disease is absent

Early detection Demonstrate freedom

Biosensors monitor samples from the ___ with a timeliness of ____ hours after an agent is released; representativeness, sensitivity

Environment 12-36 hours Representativeness: discrete locations only Sensitivity: does not confirm human exposure

"Representative" representativeness: prevalence in a population is EQUAL//LESS THAN//NOT EQUAL to the prevalence in the sample

Equal

Sampling: deciding sampling units

Group (herd), individual, udder quarter, etc.

Passive surveillance is reliant upon ... to report cases of disease, and the primary advantage is ____, but a disadvantage is the possibility of ...

Health care providers or laboratories Efficiency Incomplete date due to underreporting

Main resources required for surveillance

Human Financial Transport and communication Laboratory

Objective of "early detection"

Identify disease rapidly before significant spread

Screening: testing to identify individual with ... ; objective is either ...

Infection of disease Personal intervention Protection of the public *Measurement of prevalence in screened populations

"Risk-based" representativeness: prevalence in a population is EQUAL//LESS THAN//NOT EQUAL to the prevalence in the sample

Less than

Sampling: developing sampling frame

List of sampling units from which sample will be drawn

Active animal-based surveillance: disease/processing status

Live/heathy animals -random sampling -sentinels Specific clinical signs Slaughter

Surveillance: data collection to measure ___, ___, and ___ in populations; the objective is ...

Magnitude Changes Trends Intervention in defined populations

Uses of surveillance information

Monitoring disease trends Describing natural hx of diseases ID epidemics or new syndromes Monitoring changes in infectious agents ID areas of research Planning health policy Evaluating interventions

Types of sampling

Non-probability sampling Probability sampling

"Biased" representativeness: prevalence in a population is EQUAL//LESS THAN//NOT EQUAL TO the prevalence in the sample

Not equal to

Active surveillance involves an ONGOING//REGULAR//AD HOC search for cases and is needed for EASILY DETECTED//HARD TO DETECT diseases

Ongoing Hard to detect

Timeliness of surveillance: "categories"

Ongoing Regular Ad hoc

The majority of government surveillance systems are PASSIVE//ACTIVE

Passive

Major types of surveillance

Passive Active

Objective of "demonstration of freedom"

Provide proof of no disease

Effectiveness of surveillance is dependent upon ...

Quality Amount Distribution

Syndromic surveillance has high SENSITIVITY//SPECIFICITY and low SENSITIVITY//SPECIFICITY

Sensitivity Specificity *less severe cases may not be identified

Why should human and animal surveillance be integrated?

Shared environmental concerns Shared risk and exposure with zoonotic diseases

Syndromic surveillance: monitor ____ indicative of a disease or disorder and often uses _____ data; timeliness, representativeness

Signs/symptoms Electronic healthcare encounter data Timeliness: near "real time" Representativeness: entities willing/able to participate

"____ sample" selects a fixed percentage of the sampling frame using a formal random process, and a known probability that an individual sampling unit will be selected from the sampling frame

Simple random sample

Types of sampling: probability sampling

Simple random sampling Systematic random sampling Stratified random sampling Cluster sampling Multistage sampling

Attributes of surveillance systems

Simplicity Flexibility Data quality Sensitivity Cost Representativeness Predictive positive value

Sampling is the procedure by which ...

Some members (a subset) of a given population are selected and measured as representatives of the entire population or herd

Active animal-based surveillance is used for these specific disease programs

Srapie Bovine tuberculosis Chronic wasting disease Avian influenza

Animal health surveillance agencies in the US

State departments of agriculture USDA APHIS NAHLN

Human health surveillance agencies in the US

State/regional public health CDC FDA

Sampling: determining the required precision is dependent upon ...

Surveillance objectives

Three principles to meet surveillance objectives

Timeliness Population coverage Representativeness

Case-based surveillance: timeliness, representativeness, and sensitivity

Timeliness of reporting: days to weeks Representativeness: required ind all states Sensitivity: predetermined case definitions *list of disease/pathogens reportable to overseeing authority (varies by state)

Objective of "measuring disease"

To detect changes in the level of disease

Objective of "case finding"

To identify infected animals, flocks, or herds during a control program

Active surveillance utilizes samples or observations collected specifically for ...

Use by the surveillance program

"Case finding" surveillance should ...

Use comprehensive coverage of the population Be ongoing Have good individual herd or animal sensitivity