Outbreak Investigation
A disease outbreak is when more cases of disease occur than expected (Centers for Disease Control and Prevention, 2012). Disease outbreaks are discovered by routinely reviewing surveillance data, such as laboratory results, or linking individual actions of many people to one common experience. Health departments or tribal agencies, hospital infection control practitioners, laboratories, or other agencies all collect and review surveillance data and can identify an outbreak.
Determining how extensively a possible outbreak should be investigated, varies between health departments (Centers for Disease Control and Prevention, 2012). Factors such as the severity of an illness, number of cases, source, transmission rate, availability of prevention/control measures, and department resources and/or capacity are all factors that impact disease investigation. The purpose of outbreak investigations is to learn enough about the situation to implement appropriate control and prevention measures (Centers for Disease Control and Prevention, 2012).
If a field investigation is warranted for an outbreak, it is important to work “quick and clean” using the steps outlined below (Centers for Disease Control and Prevention, 2012). Using a systematic approach will help ensure all steps are taken and nothing is missed.
The steps of an outbreak investigation include:
- Prepare for field work
- Establish the existence of an outbreak
- Verify the diagnosis
- Construct a working case definition
- Find cases systematically and record information
- Perform descriptive epidemiology
- Develop hypotheses
- Evaluate hypotheses epidemiologically
- As necessary, reconsider, refine, and re-evaluate hypotheses
- Compare and reconcile with laboratory and/or environmental studies
- Implement control and prevention measures
- Initiate or maintain surveillance
- Communicate findings
Despite the best intentions, outbreak responses can inadvertently and disproportionality affect people who are experiencing poverty or who are historically marginalized (Kawachi, 2020). Decision makers should be aware of these inequities so they can determine how to best mitigate the health consequences of policies that impact prevention measures (Kawachi, 2020).
Watch A Guide to Outbreak Investigation (10 min).
This video describes the steps of an outbreak investigation and how infectious disease is controlled (Let’s Learn Public Health, 2017).
Watch How Association of Public Health Laboratories Contains Emerging Infectious Diseases (2 min).
Public Health Laboratories continuously work to discover, track, and respond to emerging infectious diseases. This video shows how laboratories contribute to outbreak investigations (APHL, 2016).
Complete Case Study: Legionnaires’ Disease (8 min).
This case study will highlight a Legionnaire’s disease outbreak and showcase how various public health professionals may contribute to the surveillance, investigation, and response of an outbreak.