Week 7 Flashcards
first indication that a potential outbreak of a disease occurs
increased number of new cases of disease/illness
Questions at initial stage that need immediate answering
Is there an unusual number of health outcomes in the population of interest?
Is that number stable, increasing or decreasing?
What type of exposure may have caused it?
What are the potential spread and anticipated future course of this outbreak?
Initial stages in outbreak investigation
- establish the existence of an outbreak
- verify the diagnosis
- establishing the case definition
- develop line listing and case findings
- establish the existence of an outbreak
Identify investigation team and resources required to establish the outbreak
Investigators should prepare for fieldwork and conduct tests to establish the outbreak and factors associated with it
Need to determine whether this increased number of cases is expected for the surveilled population in a specific geographic area or time period
Investigators should review the epidemiology of adverse health outcomes similar to the reported cases
- verify the diagnosis
Investigators should identify nature of disease, confirmed via clinical and lab tests
May be necessary to send investigators to visit some of the cases to confirm the initial reports
- establishing the case definition (4 components)
Clinical information about the disease
Characteristics of the persons affected
Information about the place
Specification of the time based on incubation
Case definition
standard to identify those who are cases from those who are not cases
- develop line listing and case findings
Identify cases through health care facilities
Information collected includes demographic and exposure information (risk factor), clinical information (symptom type and duration) and identification information on each individual (for follow up and debriefing)
Further stages of outbreak investigation
- develop hypotheses- perform descriptive epidemiology
- evaluate hypothesis and perform additional tests
- implementing control measures
- communicating findings and maintain surveillance
- develop hypotheses- perform descriptive epidemiology
What trends appear overtime during potential outbreak (including place and population affected)
Develop causal hypotheses
Data in the form of epic-curves helps:
Suggest the type of exposure (point-source, person to person)
Suggest time of exposure (if agent is known)
Suggest possible agents (if time of exposure is known)
- evaluate hypothesis and perform additional tests
Additional tests (case control or cohort studies) required when stage 5 does not confirm hypothesis
When to use cohort study in stage 6
assess exposed and non exposed individuals and following up to see who contracts the disease
Needs to include all exposed
Only if we have a complete list of individuals
Use RR for a measure of association
when to use case control study in stage 6
assess exposure among those who are ill and non ill
Used when a complete list is not available or too large
May include national outbreaks
Use OR for a measure of association
- implementing control measures
Measures put in place at any point during the outbreak to minimise contamination and spread
May include isolation, cohorting, product recall
Balance between preventing further disease and protecting credibility and reputation of the institution
- communicating findings and maintain surveillance
Findings of the investigation must be communicated:
Oral briefing for local health authorities: response to media attention important to address public concerns about outbreak
Written report: including all information with a blueprint for an action
Maintain Surveillance: deciding if the outbreak is over; documenting the effectiveness of control measures
In residential facilities: 7 days elapsed since resolution of symptoms in last case