Make epidemiologic associations.

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

foods).

(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

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