CHAPTER 1, FOOD SAFETY
further as confirmed or suspected. A confirmed case meets the case
definition and has laboratory evidence of infection (e.g., diarrhea and
laboratory isolation of a pathogenic bacteria), while a suspected case
meets the case definition but laboratory confirmation is lacking or
incomplete (e.g., diarrhea only).
e. Make epidemiologic associations.
(1) Although the investigation is not complete, a preliminary
assessment of available data helps to confirm that an outbreak has or has
not occurred. The investigator needs to decide if two or more persons
experienced a similar illness and that the cases are associated by time
(e.g., onset within a few hours or days of each other), place (e.g., eating
at the same establishment or event) and/or person (e.g., eating same
(2) Develop a hypothesis about the type of illness, possible
vehicles of transmission and means by which the vehicle was contaminated.
Hypotheses are possible explanations for the outbreak; more investigation
and/or more data may be necessary to prove or disprove their role in the
outbreak. Table 1-10 provides information concerning incubation periods,
clinical syndromes, and criteria for confirming the etiology once an FBDO
has been identified. The information on incubation periods and clinical
syndromes is provided as a guideline and should not be included in the
confirmation criteria. These guidelines may not include all etiologic
agents and diagnostic tests. Decisions on additional investigative efforts
(case and control finding, laboratory analyses, etc.) and their priority
should be guided by the resulting information's value in providing or
disproving the current hypotheses.
f. Provide information. Keep everyone with a "need to know" informed
of the progress and findings to the investigation. Who "needs to know"
varies with the outbreak but may include: appropriate line commanders; the
commanding officer, preventive medicine staff and/or laboratory officer of
the supporting MTF; appropriate public affairs officers (PAO); and local
health department representatives. If the situation requires informing the
public, work with a PAO or local risk communication personnel to provide
objective factual information about the outbreak and clear recommendations
on actions that the public should take. File a Medical Event Report in
accordance with BUMEDINST 6220.12 series.
g. Expand the investigation. Often the initial investigation will
identify a pathogen. The investigator may have a plausible hypothesis for
the vehicle and its method of contamination. The food service manager may
have implemented the recommendations to prevent further illness. It is
often tempting to conclude the investigation at this point. Such
superficial investigations may underestimate the true number of cases, miss
the true method of contamination, and fail to alter potentially hazardous
food handling procedures. At this point it is important to find and
interview additional persons (both ill and well) at risk. Complete food