Notes

Outline

Epidemiology & Surveillance

Learning Objectives Upon completion of this presentation, participants should be able to: Define epidemiology, and describe its relevance to various agencies and positions Understand the importance of both descriptive and analytic epidemiology

Learning Objectives, continued Define an outbreak, and list the ways by which outbreaks are typically identified Define surveillance, and identify types of surveillance and why they are conducted Specify the 10 steps of an outbreak investigation

Learning Objectives, continued Understand roles and responsibilities during an outbreak investigation Demonstrate how to distinguish naturally occurring outbreaks from bioterrorism

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination

What is Epidemiology? “The study of the distribution and determinants of disease in populations”

Descriptive Epidemiology The summary of health-related characteristics according to person, place and time Tells you the who, where and when of disease occurrence

Analytic Epidemiology The study of the causal relationships between exposures and outcomes Tells you why disease occurs

Analytic Epidemiology Causality is typically achieved by establishing hypotheses and formally evaluating these hypotheses The observed outcome of a subgroup of people with a particular exposure is compared to the expected outcome of the population as a whole  Statistical methods are used to determine if the difference between the observed outcome and the expected outcome are significantly different If so, there is likely to be a causal relationship between exposure and the outcome

Descriptive vs. Analytic Epidemiology Descriptive Who, where, when Illustrates potential associations Analytic Why Evaluates the causality of associations

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination

Practice Routine Surveillance What is surveillance? Why is surveillance important? Types of surveillance

What is Surveillance?

Why is Surveillance Important? Provides an accurate assessment of the status of health in a given population Allows for the detection of an outbreak – the occurrence of more cases of disease than expected over a defined period of time

Why is Surveillance Important? Public health surveillance data can be used to: guide disease control & prevention measures measure the burden of disease evaluate public policy detect changes in health practices prioritize the allocation of health resources describe the clinical course of disease provide a basis for epidemiologic research

Types of Surveillance Routine surveillance Active surveillance Syndromic surveillance

Routine Surveillance The ongoing systematic collection of data on specific diseases Each state has a list of notifiable diseases: diseases for which reporting of all suspected cases to public health authorities is mandated by law

Routine Surveillance in Maine The Maine Bureau of Health requires the report of Category 1 conditions immediately by telephone, and the report of Category 2 conditions within 48 hours For more information on Maine’s notifiable conditions, go to:

Routine Surveillance in Maine In Maine, the Notifiable Condition Reporting Form must include: Disease or condition Demographic information for the case-person Diagnostic laboratory findings Healthcare provider’s name & contact information

Active Surveillance The directed identification of cases of a particular disease Usually initiated by Bureau of Health Most common during an epidemic Can also be event-based

Syndromic Surveillance The use of data on symptoms that precede diagnosis to detect an outbreak Syndromic surveillance is typically automated Ideally, surveillance of symptoms instead of diagnoses allows for earlier detection Most effective when coupled with routine surveillance

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination

How are Outbreaks Recognized? Review of routinely collected surveillance data Astute observation of a sentinel event or cluster of events by a health care provider Members of the community observe unusual trend in illness

Outbreak Detection & Response

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination

Why Investigate an Outbreak? Disease control & prevention Public/political/legal concerns Program considerations Training Research

A Typical Outbreak Investigation Unexpected event… Need to investigate quickly… Pressure for answers… Multiple agencies involved… Under media spotlight… Work carried out in the field… …requires systematic approach!

Goals of Outbreak Investigation During an outbreak investigation, one typically hopes to determine the following: Characteristics of the outbreak Who is at risk of disease What exposures increase risk of disease Characteristics of the agent Source Mode of transmission

The 10 Steps of Outbreak Investigation Prepare for field work Establish the existence of an outbreak Verify the diagnosis Define & identify cases Perform descriptive epidemiology Develop hypotheses Perform analytic epidemiology Refine hypotheses & conduct additional studies Implement control & prevention measures Communicate findings

Step 1: Prepare for Field Work Before leaving for the field, one should: Research the disease Gather equipment & supplies Make necessary administrative arrangements Determine roles & responsibilities

Step 2: Establish the Existence of an Outbreak Before proceeding with the investigation, one must confirm that the suspected outbreak is a real outbreak This is done by comparing the observed number of cases to the historically expected number of cases

Step 3: Verify the Diagnosis Identify the illness as accurately as possible Requires review of clinical findings and laboratory results Also requires talking to case-patients about their illness

Step 4: Define & Identify Cases The next step is to establish a case definition: a set of standard criteria for deciding whether a person has a particular illness The case definition should include: Clinical information about the disease Information regarding person Information regarding place Information regarding time

Step 4: Define & Identify Cases The case definition should be specific enough so that not all people in Maine are identified as cases At the same time, the case definition should also be sensitive enough so that cases are not missed

Step 4: Define & Identify Cases

Step 4: Define & Identify Cases Once the case definition is established, it is used to identify additional cases

Step 5: Perform Descriptive Epidemiology Once data have been collected, the epidemic can be described in terms of person, place, and time An epidemic curve can be drawn to provide further information about the agent and source

Step 6: Develop Hypotheses Consider what is known about the disease: What is the agent’s usual reservoir? How is it usually transmitted? What are the known risk factors? “Round up the usual suspects”

Step 7: Perform Analytic Epidemiology Analyze the available data in order to formally evaluate the proposed hypotheses

Step 8: Refine Hypotheses & Conduct Additional Studies Even when your analytic study identifies an association between exposure and disease, you may need to refine your hypotheses and conduct additional, more specific studies An initial study may implicate a particular restaurant in a food-borne outbreak, while a second study may narrow the cause down to a particular menu item

Step 9: Implement Control & Prevention Measures Should be consistent with the outbreak investigation findings Should be implemented as soon as possible to prevent further infection Can range from throwing away contaminated food to administering mass prophylaxis & vaccination

Step 9: Implement Control & Prevention Measures Implement control and prevention measures as early as possible Usually target one or more: Eliminate the source Interrupt transmission Reduce susceptibility

Step 10: Communicate Findings Oral briefing for health authorities and people responsible for implementing control and prevention measures This should be accompanied by a written scientific report of the outbreak investigation

Step 10: Communicate Findings

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination

Is it Bioterrorism? Single case caused by uncommon agent without alternative explanation Unusual, atypical, genetically engineered or antiquated strain Unusually high morbidity & mortality Unusual disease presentation

Is it Bioterrorism? Unusual geographic or seasonal distribution Unexpected increase in endemic disease Atypical mode of transmission Related to common ventilation system Coexisting unusual diseases in individual(s)

Is it Bioterrorism? Unusual illness affecting large, disparate populations Unusual age group Unusual patterns in humans more so than in animals Unusual patterns in animals more so than in humans

Is it Bioterrorism? Point source with compressed epidemic curve Similar genetic isolates from disparate sources Simultaneous clusters in disparate areas Large numbers of unexplained deaths

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination

Interagency Coordination During a naturally occurring outbreak, this is the typical structure:

Interagency Coordination During a suspected bioterrorism event:

Fundamental Components of Epidemiology & Surveillance Practice routine surveillance Identify potential outbreaks Investigate each outbreak in a systematic manner Determine if bioterrorism was the cause Understand interagency coordination