What is the next step in managing an outbreak of acute gastroenteritis among hospital staff who consumed food from the same restaurant?

Next Step: Conduct a Case-Control Study

The next step is to conduct a formal case-control study (Option B) to systematically identify which specific food items from the restaurant are associated with illness through structured comparison of affected and unaffected individuals. 1

Rationale for Case-Control Study as the Immediate Priority

The outbreak has already been established with 15 of 50 staff ill with similar symptoms and common restaurant exposure. 1 The current phase of investigation requires conducting a case-control study to:

• Define cases systematically and identify appropriate controls among the 35 unaffected staff members who also ate at the restaurant 1
• Conduct structured interviews about specific food items consumed to identify the exact vehicle of infection 1
• Quantify the strength of association between suspected exposures and illness using odds ratios, as demonstrated in similar outbreaks where specific items like potato salad showed odds ratios as high as 84.0 2, 1

Why Other Options Are Premature or Inappropriate

Isolation of Affected Individuals (Option A)

• Isolation is not the priority in a foodborne outbreak investigation where the source is external to the hospital 2
• Standard infection control precautions are sufficient while the investigation proceeds 2

Quarantine of Restaurant Staff (Option C)

• Quarantining restaurant staff before identifying the specific contaminated food item wastes time and resources without epidemiologic direction 1
• The case-control study must first identify which specific food items are implicated before targeting food handler investigations 2, 1

Detailed Restaurant Data Collection (Option D)

• Environmental and laboratory investigation of the restaurant's food processing is the subsequent phase that follows after the case-control study identifies specific high-risk items 1
• Pursuing environmental investigations first without epidemiologic direction is inefficient 1

Sequential Investigation Steps

Phase 1 (Current): Conduct case-control study

• Interview all 50 staff members about specific foods consumed 2, 1
• Calculate odds ratios for each food item 2, 1

Phase 2 (Following): Environmental and laboratory investigation

• Collect samples of implicated foods for microbiologic testing 1
• Screen food handlers for infection, particularly those who prepared the implicated items 2, 1
• Exclude infected food handlers until stool cultures are negative 1

Phase 3: Implement control measures

• Provide food handler education on hygiene practices 1
• Review employee health policies with restaurant management 2

Critical Considerations

• Do not assume all restaurant exposures are equal — the case-control study identifies specific high-risk items that guide targeted interventions 1
• Do not overlook asymptomatic food handlers — they can be colonized and transmit infection without symptoms, as demonstrated in outbreaks where asymptomatic workers tested positive for Salmonella 2, 1
• Multiple pathogens may be involved — testing should include serotyping and molecular characterization if resources permit 2