What is the next step in managing an outbreak of acute gastroenteritis among hospital staff who ate at the same restaurant?

Next Step in Outbreak Management

The next step is to conduct a case-control study to identify common exposures and confirm the association between illness and specific food items from the restaurant (Option B).

Rationale for Case-Control Study

After preliminary interviews establish a common exposure (the restaurant), the standard epidemiologic approach is to conduct a formal case-control study to:

• Identify specific food items or exposures associated with illness through systematic comparison of cases and controls 1
• Quantify the strength of association between suspected exposures and illness using odds ratios 1
• Guide targeted control measures based on identified risk factors rather than broad interventions 1

The Connecticut Department of Public Health investigation demonstrates this approach: after identifying a common exposure (reception food), they immediately conducted a case-control study among attendees, comparing food consumption histories between 9 cases and 14 controls, which successfully identified potato salad as the source (OR = 84.0) 1.

Why Other Options Are Premature

Isolation of Affected Individuals (Option A)

• Not the immediate priority for gastroenteritis outbreaks, which are typically self-limited 2
• Standard infection control measures (handwashing, excluding symptomatic staff from food handling) are sufficient 1
• Isolation is reserved for specific high-risk settings or pathogens, not routine foodborne outbreaks 1

Quarantine of Restaurant Staff (Option C)

• Premature without epidemiologic confirmation that the restaurant is definitively the source 1
• Staff screening and exclusion should follow after the case-control study confirms the restaurant association 1
• Symptomatic food handlers should be excluded for at least 2 days after symptom resolution once identified 1

Detailed Restaurant Data Collection (Option D)

• Environmental investigation follows, not precedes, epidemiologic confirmation 1
• The case-control study must first establish which specific foods or practices are associated with illness 1
• Environmental audits and food sample collection are then targeted based on epidemiologic findings 3

Systematic Outbreak Investigation Algorithm

Phase 1: Establish the Outbreak (Already Completed)

• 15 of 50 staff ill with similar symptoms and common restaurant exposure 1

Phase 2: Conduct Case-Control Study (Current Step)

• Define cases (e.g., diarrhea ≥3 loose stools in 24 hours within 5 days of exposure) 1
• Identify controls (exposed individuals without illness) 1
• Conduct structured interviews about specific food items consumed 1
• Calculate odds ratios to identify implicated foods 1

Phase 3: Environmental and Laboratory Investigation

• Collect samples of implicated foods for microbiologic testing 1, 3
• Conduct environmental audit of restaurant food handling practices 3
• Screen food handlers for infection, particularly those handling implicated items 1

Phase 4: Implement Control Measures

• Exclude infected food handlers until stool cultures negative 1
• Address identified food safety violations 3
• Provide food handler education on hygiene practices 1

Critical Pitfalls to Avoid

• Do not delay the case-control study to pursue environmental investigations first—this wastes time and resources without epidemiologic direction 1
• Do not assume all restaurant exposures are equal—the case-control study identifies specific high-risk items (in one outbreak, potato salad had OR = 84.0 while other foods were not associated) 1
• Do not overlook asymptomatic food handlers—they can be colonized and transmit infection without symptoms 1
• Ensure adequate sample size for the case-control study by actively recruiting both cases and controls through contact tracing 1