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 requires conducting a case-control study to:

• Define cases precisely 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 2, 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 Misdirected

Isolation (Option A) - Not Indicated

• Isolation of affected individuals is not the priority in a foodborne outbreak investigation where person-to-person transmission is not the primary concern 2
• The focus should be on identifying the contaminated food source rather than isolating cases 1

Restaurant Staff Quarantine (Option C) - Premature

• Quarantining restaurant staff before identifying the specific contaminated food item wastes time and resources without epidemiologic direction 1
• Environmental and food handler investigations should follow after the case-control study identifies specific high-risk items 1
• Screening food handlers becomes targeted once you know which food items to investigate 2

Food Processing Data Collection (Option D) - Lacks Direction

• Collecting detailed food processing data without knowing which specific food item caused the outbreak is inefficient 1
• The case-control study provides the epidemiologic direction needed to focus environmental investigations 1

Subsequent Steps After Case-Control Study

Once the case-control study identifies the implicated food item(s), the investigation proceeds to:

1. Environmental and laboratory investigation including collecting samples of implicated foods for microbiologic testing 1
2. Screening food handlers for infection, particularly those who prepared the implicated items 2, 1
3. Excluding infected food handlers until stool cultures are negative (typically requiring two consecutive negative cultures ≥24 hours apart) 2, 1
4. Providing food handler education on hygiene practices to prevent future outbreaks 1

Critical Pitfalls to Avoid

• Do not assume all restaurant exposures are equal - the case-control study identifies specific high-risk items rather than implicating the entire menu 1
• Do not overlook asymptomatic food handlers - they can be colonized and transmit infection without symptoms, as demonstrated in the Connecticut outbreak where an asymptomatic food service worker tested positive for Salmonella 2, 1
• Do not delay the case-control study to pursue environmental investigations first, as this approach lacks epidemiologic direction and wastes critical time 1