TEPS OF AN
In the investigation of an ongoing outbreak, working quickly is essential. Getting the right answer is
essential, too. Under such circumstances, epidemiologists find it useful to have a systematic approach
to follow, such as the sequence listed below. This approach ensures that the investigation proceeds
forward without missing important steps along the way.
Steps of an outbreak investigation
1. Prepare for field work
2. Establish the existence of an outbreak
3. Verify the diagnosis
4. Define and identify cases
a. establish a case definition
b. identify and count cases
5. Perform descriptive epidemiology
6. Develop hypotheses
7. Evaluate hypotheses
8. As necessary, reconsider/refine hypotheses and execute additional studies
a. additional epidemiologic studies
b. other types of studies – laboratory, environmental
9. Implement control and prevention measures
10. Communicate findings
The steps described above are in conceptual order. In practice, however, several steps may be done
at the same time, or the circumstances of the outbreak may dictate that a different order be followed.
For example, control measures should be implemented as soon as the source and mode of
transmission are known, which may be early or late in any particular outbreak investigation.
Step 1: Preparing for Field Work
Anyone about to embark on an outbreak investigation should be well prepared before leaving for the
field. Preparations can be grouped into three categories: (a) investigation, (b) administration, and (c)
consultation. Good preparation in all three categories will facilitate a smooth field experience.
First, as a field investigator, you must have the appropriate scientific knowledge, supplies, and
equipment to carry out the investigation. You should discuss the situation with someone
knowledgeable about the disease and about field investigations, and review the applicable literature.
You should assemble useful references such as journal articles and sample questionnaires. Before
leaving for a field investigation, consult laboratory staff to ensure that you take the proper laboratory
material and know the proper collection, storage, and transportation techniques. Arrange for a laptop,
Dictaphone, camera, and other supplies.
Second, as an investigator, you must pay attention to administrative procedures. In a health agency,
you must make travel and other arrangements and get them approved. You may also need to take
care of personal matters before you leave, especially if the investigation is likely to be lengthy.
Third, as an investigator, you must know your expected role in the field. Before departure, all parties
should agree on your role, particularly if you are coming from “outside” the local area. For example,
are you expected to lead the investigation, provide consultation to the local staff who will conduct the
investigation, or simply lend a hand to the local staff? In addition, you should know who your local